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|Spotted Hyena - Crocuta Crocuta|
|Tweet Topic Started: Jan 7 2012, 08:21 AM (26,589 Views)|
|Canidae||Jan 7 2012, 08:21 AM Post #1|
Species: C. crocuta
Conservation status: Least Concern
The spotted hyena (Crocuta crocuta), also known as the laughing hyena or tiger wolf, is a species of hyena native to Sub-Saharan Africa. It is listed as Least Concern by the IUCN on account of its widespread range and large numbers estimated at 10,000 individuals. The species is however experiencing declines outside of protected areas due to habitat loss and poaching. The species may have originated in Asia, and once ranged throughout Europe for at least one million years until the end of the Late Pleistocene.
The spotted hyena is the most social of the Carnivora in that it has the largest group sizes and most complex social behaviours. Its social organisation is unlike that of any other Carnivore, bearing closer resemblance to that of cercopithecine primates (baboons and macaques) with respect to group-size, hierarchical structure, and frequency of social interaction among both kin and unrelated group-mates. However, the social system of the spotted hyena is openly competitive rather than cooperative, with access to kills, mating opportunities and the time of dispersal for males depending on the ability to dominate other clan-members. Females provide only for their own cubs rather than assist each other, and males display no paternal care. Spotted hyena society is matriarchal; females are larger than males, and dominate them.
The spotted hyena is a highly successful animal, being the most common large carnivore in Africa. Its success is due in part to its adaptability and opportunism; it is both an efficient hunter and a scavenger, with the capacity to eat and digest skin, bone and other animal waste. In functional terms, the spotted hyena makes the most efficient use of animal matter of all African carnivores. The spotted hyena displays greater plasticity in its hunting and foraging behaviour than other African carnivores; it hunts alone, in small parties of 2-5 individuals or in large groups. During a hunt, spotted hyenas often run through ungulate herds in order to select an individual to attack. Once selected, their prey is chased over long distance, often several kilmoetres, at speeds of up to 60 km/h.
Taxonomy & Evolution
Unlike the striped hyena, for which a number of subspecies were proposed in light of its extensive modern range, the spotted hyena is a genuinely variable species, both temporally and spatially. Its range once encompassed almost all of Africa and Eurasia, and displayed a large degree of morphological geographic variation, which lead to an equally extensive set of specific and subspecific epithets. It was gradually realised that all of this variation could be applied to individual differences in a single subspecies. In 1939, biologist L. Harrison Matthews demonstrated through comparisons between a large selection of spotted hyena skulls from Tanzania that all the variation seen in the then recognised subspecies could also be found in a single population, with the only set of characters standing out being pelage (which is subject to a high degree of individual variation) and size (which is subject to Bergmann's Rule). When fossils are taken into consideration, the species displayed even greater variation than it does in modern times, and a number of these named fossil species have since been classed as synonymous with Crocuta crocuta, with firm evidence of there being more than one species within the genus Crocuta still lacking.
Both Björn Kurtén and Camille Arambourg promoted an Asiatic origin for the species; Kurtén focussed his arguments on the Plio-Pleistocene taxon Crocuta sivalensis from the Siwaliks, a view defended by Arambourg, who nonetheless allowed the possibility of an Indo-Ethiopian origin. This stance was contested by Ficarelli and Torre, who referred to evidence of the spotted hyena's presence from African deposists dating from the early Pleistocene, a similar age to the Asian C. sivalensis. Studies on the phylogeographic distribution of mtDNA haplotypes indicates three migration events from Africa to Eurasia, though neither the topology of the phylogenetic tree or the fossil record exclude the possibility of an Asian origin. The earliest migration of spotted hyenas from Africa to Eurasia began less than 3.5 million years ago, most probably from the area where the first spotted hyena fossils were discovered, reaching East Asia and most likely also Pakistan. The second migration of spotted hyenas occurred less than 1.3–1.5 million years ago and resulted in the first arrival of hyenas in Europe and a separation of African spotted hyenas in a southern and a northern population. The third spotted hyena migration took place after 0.36 million years ago, starting from the northern African population and reaching both Europe and Asia. Unlike other African carnivores, with the exception of the leopard, there is no evidence to suggest that spotted hyenas underwent a genetic bottleneck during the Pleistocene.
The ancestors of the genus Crocuta diverged from Hyaena (the genus of striped and brown hyenas) 10 million years ago. The ancestors of the spotted hyena probably developed social behaviours in response to increased pressure from other predators on carcasses, which forced them to operate in teams. At one point in their evolution, spotted hyenas developed sharp carnassials behind their crushing premolars; this rendered waiting for their prey to die no longer a necessity, as is the case for brown and striped hyenas, and thus became pack hunters as well as scavengers. They began forming increasingly larger territories, necessitated by the fact that their prey was often migratory, and long chases in a small territory would have caused them to encroach into another clan's land. It has been theorised that female dominance in spotted hyena clans could be an adaptation in order to successfully compete with males on kills, and thus ensure that enough milk is produced for their cubs. Another theory is that it is an adaptation to the length of time it takes for cubs to develop their massive skulls and jaws, thus necessitating greater attention and dominating behaviours from females. Its appearance in Europe and China during the Cromerian period coincided with the decline and eventual extinction of Pachycrocuta brevirostris, the giant short-faced hyena. As there is no evidence of environmental change being responsible, it is likely that the giant short-faced hyena became extinct due to competition with the spotted hyena.
The spotted hyena has a strong and well developed neck and forequarters, but relatively underdeveloped hindquarters. The rump is rounded rather than angular, which prevents attackers coming from behind from getting a firm grip on it. The head is wide and flat with a blunt muzzle and broad rhinarium. In contrast to the striped hyena, the ears of the spotted hyena are rounded rather than pointed. Each foot has four digits, which are webbed and armed with short, stout and blunt claws. The paw-pads are broad and very flat, with the whole undersurface of the foot around them being naked. The tail is relatively short, being 300–350 mm long, and resembles a pompom in appearance. Unusually among hyaenids, and mammals in general, the female spotted hyena is considerably larger than the male. Both sexes have a pair of anal glands which open into the rectum just inside the anal opening. These glands produce a white, creamy secretion which is pasted onto grass stalks by everting the rectum. The odour of this secretion is very strong, smelling of boiling cheap soap or burning, and can be detected by humans several metres downwind. The spotted hyena has a proportionately large heart, constituting close to 1% of its body weight, thus giving it great endurance in long chases. In contrast, a lion's heart makes up only 0.45-0.57 percent of its body weight. The now extinct Eurasian populations were distinguished from the modern African populations by their shorter distal extremities and longer humerus and femur.
The skull of the spotted hyena differs from that of the striped hyena by its much greater size and narrower sagittal crest. For its size, the spotted hyena has one of the most powerfully built skulls among the Carnivora. The dentition is more dual purposed than that of other modern hyena species, which are mostly scavengers; the upper and lower third premolars are conical bone-crushers, with a third bone-holding cone jutting from the lower fourth premolar. The spotted hyena also has its carnassials situated behind its bone-crushing premolars, the position of which allows it to crush bone with its premolars without blunting the carnassials. Combined with large jaw muscles and a special vaulting to protect the skull against large forces, these characteristics give the spotted hyena a powerful bite which can exert a pressure of 800 kgf/cm2 (11,400 lbf/in²), which is 40% more force than a leopard can generate. The jaws of the spotted hyena outmatch those of the brown bear in bonecrushing ability, and free ranging hyenas have been observed to crack open the long bones of giraffes measuring 7 cm in diameter.
The spotted hyena is the largest extant member of the Hyaenidae. Adults measure 95.0—165.8 cm in body length, and have a shoulder height of 70.0-91.5 cm. Adult male spotted hyenas in the Serengeti weigh 40.5—55.0 kg (89—121 lb), while females weigh 44.5—63.9 kg (98—141 lb). Spotted hyenas in Zambia tend to be heavier, with males weighing on average 67.6 kg (149 lb), and females 69.2 kg (153 lb). Exceptionally large weights of 81.7 kg (180 lb) and 86 kg (190 lb) are known. It has been estimated that adult members of the now extinct Eurasian populations weighed 102 kg (225 lbs).
Fur colour varies greatly and changes with age. Unlike the fur of the striped and brown hyena, that of the spotted hyena consists of spots rather than stripes and is much shorter, lacking the well defined spinal mane of the former two species. The base colour generally is a pale greyish-brown or yellowish-grey on which an irregular pattern of roundish spots is superimposed on the back and hind quarters. The spots, which are of variable distinction, may be reddish, deep brown or almost blackish. The spots vary in size, even on single individuals, but are commonly 20 mm in diameter. A less distinct spot pattern is present on the legs and belly but not on the throat and chest. A set of five, pale and barely distinct bands replace the spots on the back and sides of the neck. A broad, medial band is present on the back of the neck, and is lengthened into a forward facing crest. The crest is mostly reddish-brown in colour. The crown and upper part of the face is brownish, save for a white band above both eyes, though the front of the eyes, the area around the rhinarium, the lips and the back portion of the chin are all blackish. The limbs are spotted, though the feet vary in colour, from light brown to blackish. The fur is relatively sparse and consists of two hair types; moderately fine underfur (measuring 15–20 mm) and long, stout bristle hairs (30–40 mm). European Paleolithic rock art depicting the species indicates that the Eurasian populations retained the spots of their modern-day African counterparts.
Although the genitalia of the male spotted hyena is not unusual, that of the female closely resembles that of the male; the clitoris is shaped and positioned like a penis, and is capable of erection. The female also possesses no external vagina, as the labia are fused to form a pseudo-scrotum. The pseudo-penis is traversed to its tip by a central urogenital canal, through which the female urinates, copulates and gives birth. This unusual trait makes mating more laborious for the male than in other mammals, whilst also ensuring that rape is physically impossible. The pseudo-penis can be distinguished from the males' genitalia by its greater thickness and more rounded glans. The formation of the pseudo-penis appears largely androgen independent, as the pseudo-penis appears in the female fetus before differentiation of the fetal ovary and adrenal gland. After parturition, the pseudo-penis is stretched, and loses much of its original aspects; it becomes a slack-walled and reduced prepuce with an enlarged orifice with split lips.
The spotted hyena is a social animal which lives in large communities called "clans", which can consist of up to 80 individuals. Group-size varies geographically; in the Serengeti, where prey is migratory, clans are smaller than those in the Ngorongoro Crater, where prey is sedentary. Spotted hyena clans are more compact and unified than wolf packs, but are not as closely knit as those of African wild dogs. Females dominate males, with even the lowest ranking females being dominant over the highest ranking males. It is typical for females to remain with their natal clan, thus large clans usually contain several matrilines, whereas males typically disperse from their natal clan at the age of 2½ years. The clan is a fission-fusion society, in which clan-members do not often remain together, but may forage alone or in small groups. High-ranking hyenas maintain their position through aggression directed against lower-ranking clan-members. Spotted hyena hierarchy is nepotistic; the offspring of dominant females automatically outrank adult females subordinate to their mother. However, rank in spotted hyena cubs is greatly dependent on the presence of the mother; low-ranking adults may act aggressively toward higher-ranking cubs when the mother is absent. Although individual spotted hyenas only care for their own young, and males take no part in raising their young, cubs are able to identify relatives as distantly related as great-aunts. Also, males associate more closely with their own daughters rather than unrelated cubs, and the latter favour their fathers by acting less aggressively toward them.
Spotted hyena societies are more complex than those of other carnivorous mammals, and are remarkably similar to those of cercopithecine primates in respect to group size, structure, competition and cooperation. Like cercopithecine primates, spotted hyenas use multiple sensory modalities, recognise individual conspecifics, are conscious that some clan-mates may be more reliable than others, recognise 3rd party kin and rank relationships among clan-mates, and adaptively use this knowledge during social decision making. Also, like cercopithecine primates, dominance ranks in hyena societies are not correlated with size or aggression, but with ally networks. In this latter trait, the spotted hyena further show parallels with primates by acquiring rank through coalitions. However, rank reversals and overthrows in spotted hyena clans are very rare.
Territory size is highly variable, ranging from less than 40 km² in the Ngorongoro Crater to over 1,000 km² in the Kalahari. Home ranges are defended through vocal displays, scent marking and boundrary patrols. Clans mark their territories by either pasting or pawing in special latrines located on clan range boundraries. Clan boundraries are usually respected; hyenas chasing prey have been observed to stop dead in their tracks once their prey crosses into another clan's range. Hyenas will however ignore clan boundraries in times of food shortage. Males are more likely to enter another clan's territory than females are, as they are less attached to their natal group and will leave it when in search of a mate. Hyenas travelling in another clan's home range typically exhibit bodily postures associated with fear, particularly when meeting other hyenas. An intruder can be accepted into another clan after a long period of time if it persists in wandering into the clan's territory, dens or kills.
Reproduction and Development
The spotted hyena is a non-seasonal breeder, though a birth peak does occur during the wet season. Females are polyestrus, with an estrus period lasting two weeks. Like many felid species, the spotted hyena is promiscuous, and no enduring pair bonds are formed. Members of both sexes may copulate with several mates over the course of several years. Males will show submissive behaviour when approaching females in heat, even if the male outweighs its partner. Females usually favour younger males born or joined into the clan after they were born. Older females show a similar preference, with the addition of preferring males with whom they have had long and friendly prior relationships. Passive males tend to have greater success in courting females than aggressive ones. Copulation in spotted hyenas is a relatively short affair, which typically only occurs at night with no other hyenas present. The mating process is complicated, as the female's reproductive tract is entered and exited through her pseudo-penis rather than directly through the vagina, which is blocked by the false scrotum and testes. Once the female retracts her clitoris, the male enters the female by sliding beneath her, an operation facilitated by the penis' upward angle. Once this is accomplished, a normal mating stance is adopted.
The length of the gestation period tends to vary greatly, though 110 days is the average length of time. In the final stages of pregnancy, dominant females provide their developing offspring with higher androgen levels than lower-ranking mothers do. The higher androgen levels - the result of high concentrations of ovarian androstenedione - are thought to be responsible for the extreme masculinization of female behavior and morphology. This has the effect of rendering the cubs of dominant females more aggressive and sexually active than those of lower ranking hyenas; high ranking male cubs will attempt to mount females earlier than lower ranking males. The average litter consists of two cubs, with three occasionally being reported. Males take no part in the raising of young. Parturition is difficult, as females give birth through their narrow clitoris, and spotted hyena cubs are the largest carnivoran young relative to their mothers' weight. During parturition, the clitoris ruptures in order to facilitate the passage of young, and may take weeks to heal. Cubs are born with soft, brownish black hair, and weigh 1.5 kg on average. Unique among carnivorous mammals, spotted hyenas are also born with their eyes open and with 6–7 mm long canine teeth and 4 mm long incisors. Also, cubs will attack each other shortly after birth. This is particularly apparent in same sexed litters, and can result in the death of the weaker cub. This neonatal siblicide kills an estimated 25% of all hyenas in their first month. Male cubs which survive grow faster and are likelier to achieve reproductive dominance, while female survivors eliminate rivals for dominance in their natal clan. Lactating females can carry 3–4 kg (6.5-9 lb) of milk in their udders.Spotted hyena milk has the highest protein content of any terrestrial carnivore, and its fat content is second only to that of the polar bear and sea otter. Cubs will nurse from their mother for 12–16 months, though they can process solid food as early as three months. Mothers do not regurgitate food for their young.Females are very protective of their cubs, and will not tolerate other adults, particularly males, approaching them. Spotted hyenas exhibit adult behaviours very early in life; cubs have been observed to ritually sniff each other and mark their living space before the age of one month. Within ten days of birth, they are able to move at considerable speed. Cubs begin to lose the black coat and develop the spotted, lighter coloured pelage of the adults at 2–3 months. They begin to exhibit hunting behaviours at the age of eight months, and will begin fully participating in group hunts after their first year. Spotted hyenas reach sexual maturity at the age of three years. The average lifespan in zoos is 12 years, with a maximum of 25 years.
The clan's social life revolves around a communal den. While some clans may use particular den sites for years, others may use several different dens within a year or several den sites simultaneously. Spotted hyena dens can have more than a dozen entrances, and are mostly located on flat ground. The tunnels are usually oval in section, being wider than they are high, and narrow down from an entrance width of ½-1 metre to as small as 25 cm. In the rocky areas of East Africa and Congo, spotted hyenas use caves as dens, while those in the Serengeti use kopjes as resting areas in daylight hours. Dens have large bare patches around their entrances, where hyenas move or lie down on. Because of their size, adult hyenas are incapable of using the full extent of their burrows, as most tunnels are dug by cubs or smaller animals. The structure of the den, consisting of small underground channels, is likely an effective anti-predator device which protects cubs from predation during the absence of the mother. Spotted hyenas rarely dig their own dens, having been observed for the most part to use the abandoned burrows of wathogs, springhares and jackals. Faeces are usually deposited 20 metres away from the den, though they urinate wherever they happen to be. Dens are used mostly by several females at once, and it is not uncommon to see up to 20 cubs at a single site. The general form of a spotted hyena den is tunnel-shaped, with a spacious end chamber used for sleeping or breeding. This chamber measures up to 2 metres in width, the height being rather less. Females generally give birth at the communal den or a private birth den. The latter is primarily used by low status females in order to maintain continual access to their cubs, as well as ensure that they become acquainted with their cubs before transferral to the communal den.
Unlike other large African carnivores, spotted hyenas do not preferentially prey on any species, and only buffalo, giraffe and plains zebra are significantly avoided. Spotted hyenas prefer prey with a body mass range of 56–182 kg, with a mode of 102 kg. When hunting medium to large sized prey, spotted hyenas tend to select certain categories of animal; young animals are frequently targeted, as are old ones, though the latter category is not so significant when hunting zebras, due to their aggressive antipredator behaviours. The spotted hyena tracks live prey by sight, hearing and smell. Carrion is detected by smell and the sound of other predators feeding. During daylight hours, it watches vultures descending upon carcasses. Its auditory perception is powerful enough for it to detect sounds of predators killing prey or feeding on carcasses over distances of upt to 10 km. Unlike the grey wolf, the spotted hyena relies more on sight than smell when hunting, and does not follow its prey's prints or travel in single file. Small prey is killed by being shaken in the mouth, while large prey is eaten alive.
Spotted hyenas usually hunt wildebeest either singly, or in groups of two or three. They catch adult wildebeest usually after 5 km chases at speeds of up to 60 km/h. Chases are usually initiated by one hyena and, with the exception of cows with calves, there is little active defense from the wildebeest herd. Wildebeest will sometimes attempt to escape hyenas by taking to water though, in such cases, the hyenas almost invariably catch them. Zebras require different hunting methods to those used for wildebeest, due to their habit of running in tight groups and aggressive defence from stallions. Typical zebra hunting groups consist of 10-25 hyenas, though there is one record of a hyena killing an adult zebra unaided. During a chase, zebras typically move in tight bunches, with the hyenas pursuing behind in a crescent formation. Chases are usually relatively slow, with an average speed of 15–30 km/h. A stallion will attempt to place itself between the hyenas and the herd, though once a zebra falls behind the protective formation it is immediately set upon, usually after a chase of 3 km. Though hyenas may harass the stallion, they usually only concentrate on the herd and attempt to dodge the stallion's assaults. Unlike stallions, mares typically only react aggressively to hyenas when their foals are threatened. Unlike wildebeest, zebras rarely take to water when escaping hyenas. When hunting Thompson's gazelles, spotted hyenas usually operate alone, and prey primarily on young fawns. Chases against both adult and young gazelles can cover distances of 5 km with speeds of 60 kmph. Female gazelles do not defend their fawns, though they may attempt to distract hyenas by feigning weakness.
The spotted hyena is the most carnivorous member of the Hyaenidae, and is better equipped for scavenging than other African predators; not only is it able to splinter and eat the largest ungulate bones, it is also able to digest them completely. Spotted hyenas can digest all organic components in bones, not just the marrow. Any inorganic material is excreted with the faeces, which consist almost entirely of a white powder with few hairs. They react to alighting vultures more readily than other African carnivores, and are more likely to stay in the vicinity of lion kills or human settlements. Wildebeest are the most commonly taken medium sized ungulate prey item in both Ngorongoro and the Serengeti, with zebra and Thomson's gazelles coming close behind. Cape buffalo are rarely attacked due to differences in habitat preference, though adult bulls have been recorded to be taken on occasion. In Kruger National Park, blue wildebeest, cape buffalo, Burchell's zebra, greater kudu and impala are the spotted hyena's most important prey, while giraffe, impala, wildebeest and zebra are its major food sources in the nearby Timbavati area. Springbok and kudu are the main prey in Namibia's Etosha National Park, and springbok in the Namib. In the southern Kalahari, gemsbok, wildebeest and springbok are the principal prey. In Chobe, the spotted hyena's primary prey consists of migratory zebra and resident impala. In Kenya's Masai Mara, 80% of the spotted hyena's prey consists of topi and Thomson's gazelle, save for during the four month period when zebra and wildebeest herds migrate to the area. Bushbuck, suni and buffalo are the dominant prey items in the Aberdare Mountains, while Grant's gazelle, gerenuk, sheep, goats and cattle are likely preyed upon in northern Kenya. In west Africa, it is thought that the spotted hyena is primarily a scavenger, but will occasionally attack domestic stock and medium-size antelopes in some areas. In Cameroon, it is common for spotted hyenas to feed on small antelopes like kob, but may also scavenge on reedbuck, kongoni, buffalo, giraffe, African elephant, topi and roan antelope carcasses. Records indicate that spotted hyenas in Malawi feed on medium to large-sized ungulates such as waterbuck and impala. In Tanzania's Selous Game Reserve, spotted hyenas primarily prey on wildebeest, followed by buffalo, zebra, impala, giraffe, reedbuck and kongoni. In Uganda, it is thought that the species primarily preys on birds and reptiles, while in Zambia it is primarily a scavenger. Spotted hyenas have also been found to catch fish, tortoises, humans, black rhino, hippo calves, young African elephants, pangolins and pythons.There is at least one record of four hyenas killing an adult hippopotamus in Kruger National Park. The fossil record indicates that the now extinct European spotted hyenas primarily fed on Przewalski's horses, Irish elk, reindeer, red deer, roe deer, fallow deer, wild boar, ibex, steppe wisent, aurochs, and woolly rhinoceros. Spotted hyenas are thought to be responsible for the dis-articulation and destruction of some cave bear skeletons. Such large carcasses were an optimal food resource for hyenas, especially at the end of winter, when food was scarce. Spotted hyenas may consume leather articles such as boots and belts around campsites. Jane Goodall recorded spotted hyenas attacking or savagely playing with the exterior and interior fittings of cars, and the species is thought to be responsible for eating car tyres.
A single spotted hyena can eat at least 14.5 kg of meat per meal. Although spotted hyenas act aggressively toward each other when feeding, they compete with each other mostly through speed of eating, rather than by fighting as lions do. When feeding on an intact carcass, spotted hyenas will first consume the meat around the loins and anal region, then open the abdominal cavity and pull out the soft organs. Once the stomach, its wall and contents are consumed, the hyenas will eat the lungs and abdominal and leg muscles. Once the muscles have been eaten, the carcass is disassembled and the hyenas carry off pieces to eat in peace. Spotted hyenas are adept at eating their prey in water: they have been observed to dive under floating carcasses to take bites, then resurface to swallow. A single hyena can take less than two minutes in eating a gazelle fawn, while a group of 35 hyenas can completely consume an adult zebra in 36 minutes.Spotted hyenas do not require much water, and typically only spend 30 seconds drinking.
Enemies and Competition
In areas where spotted hyenas and lions are sympatric, the two species occupy the same ecological niche, and are thus in direct competition with one another. In some cases, the extent of dietary overlap can be as high as 68.8%. Lions typically ignore spotted hyenas, unless they are on a kill or are being harassed by them. Lions will readily appropriate the kills of spotted hyenas; in the Ngorongoro crater, it is common for lions to subsist largely on kills stolen from hyenas. Lions are quick to follow the calls of hyenas feeding, a fact demonstrated by field experiments, during which lions repeatedly approached whenever the tape-recorded calls of hyenas feeding were played. When confronted on a kill by lions, spotted hyenas will either leave or wait patiently at a distance of 30–100 metres until the lions have finished eating. In some cases, spotted hyenas are bold enough to feed alongside lions, and may occasionally force lions off a kill. This mostly occurs during the nighttime, when hyenas are bolder. Spotted hyenas usually prevail against groups of lionesses unaccompanied by males if they outnumber them 4:1. The two species may act aggressively toward one another even when there is no food at stake. Lions may charge at hyenas and maul them for no apparent reason; one male lion was filmed killing two hyenas on separate occasions without eating them, and lion predation can account for up to 71% of hyena deaths in Etosha. Spotted hyenas have adapted to this pressure by frequently mobbing lions which enter their territories and will attack and kill old or young lions in particular. Experiments on captive spotted hyenas revealed that specimens with no prior experience with lions act indifferently to the sight of them, but will react fearfully to the scent.
Although cheetahs and leopards preferentially prey on smaller animals than those hunted by spotted hyenas, hyenas will steal their kills when the opportunity presents itself. Cheetahs are usually easily intimidated by hyenas, and put up little resistance, while leopards, particularly males, may stand up to hyenas. There are records of some male leopards preying on young hyenas. Hyenas are nonetheless dangerous opponents for leopards; there is at least one record of a young adult male leopard dying from a septicemia infection caused by wounds inflicted by a spotted hyena.
Spotted hyenas will follow packs of African wild dogs in order to appropriate their kills. They will typically inspect areas where wild dogs have rested and eat any food remains they find. When approaching wild dogs at a kill, solitary hyenas will approach cautiously and attempt to take off with a piece of meat unnoticed, though they may be mobbed by the dogs in the attempt. When operating in groups, spotted hyenas are more successful in pirating dog kills, though the dog's greater tendency to assist each other puts them at an advantage against spotted hyenas, who rarely work in unison. Cases of dogs scavenging from spotted hyenas are rare. Although wild dog packs can easily repel solitary hyenas, on the whole, the relationship between the two species is a one sided benefit for the hyenas, with wild dog densities being negatively correlated with high hyena populations.
Spotted hyenas dominate other hyena species wherever their ranges overlap. Brown hyenas encounter spotted hyenas in the Kalahari, where the brown species outnumbers the spotted. The two species typically encounter each other on carcasses, which the larger spotted species usually appropriate. Sometimes, brown hyenas will stand their ground and raise their manes while emitting growls. This usually has the effect of seemingly confusing spotted hyenas, which will act bewildered, though they will occasionally attack and maul their smaller cousins. Similar interactions have been recorded between spotted and striped hyenas in the Serengeti.
Jackals will feed alongside hyenas, though they will be chased if they approach too closely. Spotted hyenas will sometimes follow jackals during the gazelle fawning season, as jackals are effective at tracking and catching young animals. Hyenas do not take to eating jackal flesh readily; four hyenas were reported to take half an hour in eating a golden jackal. Overall, the two animals typically ignore each other when there is no food or young at stake.
Spotted hyenas usually keep a safe distance from Nile crocodiles. Though they readily take to water to catch and store prey, hyenas will avoid crocodile infested waters
Compared to other hyenas, the spotted hyena shows a greater relative amount of frontal cortex exclusive to motor control functions. Studies strongly suggest convergent evolution in spotted hyena and primate intelligence. A study done by evolutionary anthropologists demonstrated that spotted hyenas outperform chimpanzees on cooperative problem-solving tests; captive pairs of spotted hyenas were challenged to tug two ropes in unison to earn a food reward, successfully cooperating and learning the maneuvers quickly without prior training. Experienced hyenas even helped inexperienced clan-mates to solve the problem. In contrast, chimps and other primates often require extensive training, and cooperation between individuals is not always as easy for them. The intelligence of the spotted hyena was attested to by Dutch colonists in 19th century South Africa, who noted that hyenas were exceedingly cunning and suspicious, particularly after successfully escaping from traps. Spotted hyenas seem to plan on hunting specific species in advance; hyenas have been observed to indulge in activities such as scent marking before setting off to hunt zebras, a behaviour which does not occur when they target other prey species. Also, spotted hyenas have been recorded to utilise deceptive behaviour, including giving alarm calls during feeding when no enemies are present, thus frightening off other hyenas and allowing them to temporarily eat in peace. Similarly, mothers will emit alarm calls in attempting to interrupt attacks on their cubs by other hyenas.
Spotted hyenas have a complex set of postures in communication. When afraid, the ears are folded flat, and are often combined with baring of the teeth and a flattening of the mane. When attacked by other hyenas or by wild dogs, the hyena lowers its hindquarters. Before and during an assertive attack, the head is held high with the ears cocked, mouth closed, mane erect and the hindquarters high. The tail usually hangs down when neutral, though it will change position according to the situation. When a high tendency to flee an attacker is apparent, the tail is curled below the belly. During an attack, or when excited, the tail is carried forward on the back. An erect tail does not always accompany a hostile encounter, as it has also been observed to occur when a harmless social interaction occurs. Although they do not wag their tails, spotted hyenas will flick their tails when approaching dominant animals or when there is a slight tendency to flee. When approaching a dominant animal, subordinate spotted hyenas will walk on the knees of their forelegs in submission. Greeting ceremonies among clan-members consist of two individuals standing parallel to each other and facing opposite directions. Both individuals raise their hind legs and lick each others' anogenital area.
It is said that feasting Hyaenas engage in violent fights, and there is such a croaking, shrieking and laughing at such times that a superstitious person might really think all the inhabitants of the infernal regions had been let loose.
—Alfred Brehm (1895)
The spotted hyena has an extensive vocal range, with sounds ranging from whoops, fast whoops, grunts, groans, lows, giggles, yells, growls, soft grunt-laughs, loud grunt-laughs, whines and soft squeals. The loud "who-oop" call, along with the maniacal laughter, are among the most recognisable sounds of Africa. Typically, very high-pitched calls indicate fear or submission, while loud, lower-pitched calls express aggression. The pitch of the laugh indicates the hyena's age, while variations in the frequency of notes used when hyenas make noises convey information about the animal's social rank.
Disease and Parasites
Spotted hyenas may contract brucellosis, rinderpest and anaplasmosis. They are vulnerable to Trypanosoma congolense, which is contracted by consuming already infected herbivores, rather than through direct infection from tsetse flies. It is known that adult spotted hyenas in the Serengeti have antibodies against rabies, canine herpes, canine brucella, canine parvovirus, feline calysi, leptospirosis, bovine brucella, rinderpest and anaplasmosis. During the canine distemper outbreak during 1993-1994, molecular studies indicated that the viruses isolated from hyenas and lions were more closely related to each other than to the closest canine distemper virus in dogs. Evidence of canine distemper in spotted hyenas has also been recorded in the Masai Mara. Exposure to rabies does not cause clinical symptoms or affect individual survival or longevity. Analyses of several hyena saliva samples showed that the species is unlikely to be a rabies vector, thus indicating that the species catches the disease from other animals rather than from intraspecifics. The microfilaria of Dipetalonema dracuneuloides have been recorded in spotted hyenas in northern Kenya. The species is known to carry at least three cestode species of the genus Taenia, non of which are harmful to humans. It also carries protozoan parasites of the genus Hepatozoon in the Serengeti, Kenya and South Africa. Spotted hyenas may act as hosts in the life-cycles of various parasites which start life in herbivores ; Taenia hyaenae and T. olnogojinae occur in hyenas in their adult phase. Trichinella spiralis are found as cysts in hyena muscles.
Range, Habitat and Population
The spotted hyena's distribution once ranged in Europe from the Iberian Peninsula to the Urals, where it remained for at least one million years. Remains have also been found in the Russian Far East, and it has been theorised that the presence of hyenas there may have delayed the colonisation of North America. The causes of the species' extinction in Eurasia are still largely unknown. In Western Europe at least, the spotted hyena's extinction coincided with a decline in grasslands 12,500 years ago. Europe experienced a massive loss of lowland habitats favoured by spotted hyenas, and a corresponding increase in mixed woodlands. Spotted hyenas, under these circumstances, would have been outcompeted by wolves and humans which were as much at home in forests as in open lands, and in highlands as in lowlands. Spotted hyena populations began to shrink after roughly 20,000 years ago, completely disappearing from Western Europe between 14-11,000 years ago, and earlier in some areas.
Historically, the spotted hyena was widespread throughout Sub-Saharan Africa. It is present in all habitats save for the most extreme desert conditions, tropical rainforests and the top of alpine mountains. Its current distribution is patchy in many place, especially in West Africa. Populations are concentrated in protected areas and surrounding land. There is a continuous distribution over large areas of Ethiopia, Kenya, Tanzania, Botswana, Namibia and the Transvaal Lowvkel areas of South Africa.
Relationships with Man : Livestock predation, human attacks and grave desecration.
When targeting livestock, the spotted hyena primarily preys upon cattle, sheep and goats, though hyenas in the southern parts of Ethiopia's Tigray region preferentially target donkeys. Reports of livestock damage are often not substantiated, and hyenas observed scavenging on a carcass may be mistaken for having killed the animal. The rate at which the species targets livestock may depend on a number of factors, including stock keeping practices, the availability of wild prey and human-associated sources of organic material, such as rubbish. Surplus killing has been recorded in South Africa's eastern Cape Province. Attacks on stock tend to be fewer in areas where livestock is coralled by thorn fences and where domestic dogs are present. One study in northern Kenya revealed that 90% of all cases of livestock predation by hyenas occurred in areas outside the protection of thorn fences.
As with most mammalian predators, the spotted hyena is typically shy in the presence of humans, and has the highest flight distance (up to 300 metres) among African carnivores. However, this distance is reduced during the night, when hyenas are known to follow people closely. Although spotted hyenas do prey on humans in modern times, such incidences are rare. However, attacks on humans by spotted hyenas are likely to be underreported. Man-eating spotted hyenas tend to be very large specimens; a pair of man-eating hyenas, responsible for killing 27 people in Mlanje, Malawi in 1962 and were weighed at 72 kg (159 lb) and 77 kg (170 lb) after being shot. Victims of spotted hyenas tend to be women, children and sick or infirm men, and there are numerous cases of biologists in Africa being forced up trees in order to escape them. Attacks occur most commonly in September, when many people sleep outdoors, and bush fires make the hunting of wild game difficult for hyenas.
In 1903, Hector Duff wrote of how spotted hyenas in the Mzimba district of Angoniland would wait at dawn outside people's huts and attack them when they opened their doors. In 1908-09 in Uganda, spotted hyenas regularly killed sufferers of African sleeping sickness as they slept outside in camps. Spotted hyenas are widely feared in Malawi, where they have been known to occasionally attack people at night, particularly during the hot season when people sleep outside. Hyena attacks were widely reported in Malawi's Phalombe plain, to the north of Michesi Mountain. Five deaths were recorded in 1956, five in 1957 and six in 1958. This pattern continued until 1961 when eight people were killed. During the 1960s, Flying Doctors received over two dozen cases of hyena attacks on humans in Kenya. An anecdotal 2004 news report from the World Wide Fund for Nature indicates that 35 people were killed by spotted hyenas during a 12 month period in Mozambique along a 20 km stretch of road near the Tanzanian border.
Although attacks against living humans are rare, the spotted hyena readily feeds on human corpses. In the tradition of the Maasai and the Hadza, corpses are left in the open for spotted hyenas to eat. A corpse rejected by hyenas is seen as having something wrong with it, and liable to cause social disgrace, therefore it is not uncommon for bodies to be covered in fat and blood from a slaughtered ox. In Ethiopia, hyenas were reported to feed extensively on the corpses of victims of the 1960 attempted coup and the Red Terror. Hyenas habituated to scavenging on human corpses may develop bold behaviours towards living people; hyena attacks on people in southern Sudan increased during the Second Sudanese Civil War, when human corpses were readily available to them.
- Hans Kruuk : The Spotted Hyena: A Study of Predation and Social Behaviour.
Will add more later!
|Wolf Eagle||Jan 7 2012, 09:14 AM Post #2|
M E G A P H Y S E T E R
Great profile. Here are some pictures:
|Canidae||Jan 9 2012, 08:07 PM Post #3|
Hyena impact and relations with Ngorongoro Lions, O.P'ed by Taipan -
Top-down population regulation of a top predator:
lions in the Ngorongoro CraterBernard M. Kissui and Craig Packer- Department of Ecology, Evolution and Behavior, University of Minnesota
The ratio of lions to hyenas living in Crater has changed over time, with the rapid decline of lions in the 1960's due to disease, and their subsequent recovery -
"Despite the relatively small size of the lion population in
recent years, the hyena–lion population ratio was only
4.2 : 1 in the late 1990s (Ho¨ner et al. 2002) compared with
an estimated 14 : 1 in the late 1960s (Kruuk 1972) when
the lion population was nevertheless able to grow rapidly.
Some of the key findings in relation to the Spotted Hyena include -
"Spotted hyenas are most successful in stealing carcasses from lions when they greatly outnumber them, and hyenas are far less successful at supplanting male lions than females."
"Ho¨ner et al. (2002) report 22 cases in which hyenas obtained carcasses from lions during 1996–1999. However, during our low-density study periods in 1999–2000, we observed lions feeding from more than 260 carcasses, but hyenas never succeeded in supplanting the lions. We observed the hyenas waiting until the lions had finished the meat and scavenging the bones and skin only after the lions had moved off."
"Kruuk (1972) found that the Crater lions stole more food from spotted hyenas than vice versa in the 1960s, and Hanby et al. (1995) found that the Crater lions obtained 21% of their prey biomass from hyenas while losing no edible biomass to hyenas in 1976–1977. Ho¨ner et al. (2002) suggested that the situation had changed by the late 1990s, but our data do not support their proposition. While large groups of hyenas may occasionally take kills from the Crater lions, we observed hyenas feeding on scraps only after the lions had left voluntarily. In fact, Ho¨ner et al.’s data confirm that lions usually surrender a carcass only after they have eaten their fill. In the hyena ‘takeovers’ that Ho¨ner et al. observed in detail, the lions had already eaten at least 13 kg per capita in 11 out of 16 cases. Since lions eat 8 kg per day when prey is superabundant (Packer et al. 1990) hyenas prevented lions from exceeding their daily requirement only five times during Ho¨ner et al.’s entire study."
Prey selection differences -
"Finally, even though lions and hyenas specialize on the same prey species and might therefore be expected to suffer from exploitation competition, lions were significantly more likely to kill adults whereas hyenas took more juveniles (p < 0.01 for buffalo and p < 0.02 for wildebeest).Thus, the two species show a degree of niche separationby specializing on different age–sex classes.
"Finally, there is scant evidence of ‘exploitation competition’ between lions and hyenas: lions preferentially feed on buffalo versus wildebeest for hyenas, and lions mostly capture adult buffalo and wildebeest whereas hyenas specialize on juveniles of these two species."
|Canidae||Jan 9 2012, 08:08 PM Post #4|
Bite force / bone-crushing comparison with a Brown Bear (Ursus Arctos), O.P'ed by Mighty Kharza -
Among the Carnivora, the Hyaenidae is the best known for the bone-eating habits of most of its living members and the most derived of these is the spotted hyena, Crocuta crocuta (Werdelin and Solounias, 1991). Savage (1955) reported an experiment in which he fed horse humeri to the spotted hyena and the brown bear (Ursus arctos); the bear tried valiantly to crack the bone but was unable to remove more than a few small flakes, whereas the spotted hyena had no difficulty in fracturing the bone. I recently fed a series of vertebrae of domestic cow to several spotted hyenas in the Berkeley hyena colony; none of these individuals required more than three or four minutes to fracture and consume a vertebra.
|Canidae||Jan 9 2012, 08:10 PM Post #5|
Hyena info O.P'ed by Taipan -
"Hyenas: scavengers of the Savanna"
PSA Journal, March, 2005 by Derek Slattery
Spotted Hyena (Crocuta crocuta)
The fully grown Spotted Hyena stands around 32-36 inches, weighing between 100-170 pounds; it is powerfully built with a sloping back, a broad head with large eyes and short rounded ears. The coat is short, light brown for adults with irregularity but entirely marked with blackish rounded spots. The lace, muzzle, and the lower parts of the limbs are dark brown while the throat is lighter colored and unspotted: the short mane on the neck and shoulders bristle when alerted by danger; the tail which is fairly short stands erect when the animal is challenged.
Hyena dens are often abandoned warthog burrows or under rocky boulders especially in plains where there are no natural cavities. The Spotted Hyena lives singly or in pairs but occasionally in small packs of up to eight individuals, often at a carcass left by lions. The sense of smell is very acute and plays the largest part in the life of the Hyena for mutual recognition and for finding its way to carrion or other food. But sight is equally important as hyenas follow vultures to the spot where the birds congregate using them as pointers to food; the sense of hearing is good as well.
The Spotted Hyena is reputed to be a scavenger and actually feeds on carrion, subsisting largely on lion kills. It follows hunting lions and wild dogs from a distance and may sometimes force them off their kills; but lions, who hate hyenas and will keep them away if annoyed, can kill or mutilate the hyena when one ventures too close especially if they have young lion cubs.
The hyena is reputed to be cowardly and timid. But be aware, it can become bold and even dangerous to man, attacking human beings sleeping in the open and causing serious mutilation by biting at the face with their powerful jaws.
This hideous mammal might not be the most beautiful, but its general behavior makes interesting observation to see their true character. Observations over the years which come quickly to mind follow:
a. At the Ark in the Aberdare National Park in Kenya (sadly, too dark to photograph), a pack of 14-plus Spotted Hyenas was observed, surrounding a solitary bull buffalo at the salt lick. The buffalo stood his ground and eventually won over the hyenas that did not attack and eventually moved off in different directions leaving the buffalo to finish licking the salt from the earth.
b. In Mombo Park in Botswana just after two leopards killed an Impala, they were attacked by a hyena that chased the leopards off the kill. The hyena carried this large antelope in his jaws to the nearby bush 50 yards away, then later the older leopard returned and regained its kill and hauled the kill through the bush to the largest tree in the area which he then climbed straight up with the Impala in its mouth.
c. At Duba Plains, Okavango Delta, Botswana, our vehicle followed a hyena across an open plain (without tracks) for more than one and a half miles to photograph it carrying a large portion of a recent kill in its jaws at speeds up to 20-25 miles per hour. It was finally lost when it outpaced us running into bush or possibly its den.
d. We observed for hours in Amboseli National Park a hyena den burrowed under a rocky granite outcrop which had several burrows, noted to be shared with nearby warthogs. During the day, the hyena cubs were guarded by one adult near the den while some younger adults patrolled at some distance the surrounding area for possible danger. Most of the adults spent the day resting while they waited for the other adults to return from their daily hunt. As the sun was beginning to set, the adult hyenas returned home and were welcomed by all the cubs. First, the cubs played with the three returning adults and were cleaned before the adults regurgitated the food from their stomachs to feed the cubs. At the scene, lurking nearby, was a male warthog wanting to return home to his burrow for the night knowing he first must face the gauntlet of the three adult hyenas standing shoulder-to-shoulder protecting their cubs. He decided to challenge the three hyenas who stood ready to battle with their hackles raised; but after a short confrontation, both sides saw better of the situation even though the warthog was easily outnumbered. He slipped the hostile group and ran off to his burrow entering backwards leaving the adult hyenas annoyed."
|Canidae||Jan 9 2012, 08:14 PM Post #6|
One of Reddhole's great posts regarding Hans Kruuk's work :
Below is my summary of one of the most important studies on spotted hyenas - Hans Kruuk's book "The Spotted Hyena."
The studies were done in the Serengeti and the Ngrorongoro Crater.
In the Serengeti, the adult female hyenas weighed from
98 lbs. - 141 lbs., averaging 122 lbs. Males weighed from 89 lbs. - 121 lbs., averaging 98 lbs. These weights are almost exactly equal to the weights of wolves in Yellowstone National Park. Another study in Zambia had hyenas weigh significantly more, averaging 152 lbs. for females and 149 lbs. for males.
One interesting element of this was the signficance of lion predation as shown below:
As you can see, 57% of adult hyena deaths and 55% of all hyena deaths were due to lions, usually around kills.
Hunting Vs. Scavenging
As you can see below, hyenas in the Ngorongoro Crater hunted most of their food, but in the Serengeti a more significant amount of their food was obtained from scavenging.
The main prey animals were wildebeest, zebra and thompson's gazelle. In the Ngorongoro, hyenas had a higher percentage of adult wildebeest and zebra in their diet than the percentage these animals made up of the prey populations. The opposite was true for thompson's gazelle. Thus, hyena "preferred" wildebeest and zebra and "avoided" thompson's gazelles. The data was in reverse in the Serengeti, but this was probobly due to migrations of prey animals (which are largely confined in the Ngorongoro Crater) out of the area and/or scavenging skewing the numbers.
The 1 adult buffalo kill was an animal of unknown condition. Kruuk had observed it alive, and then dead in the same spot a few hours later with 69 hyenas feeding. The number that actually killed the buffalo was not known.
Sex of Adult Prey Killed
Hyenas killed wildbeest in the Ngorongoro Crater roughly equal to the ratio of male and female wildebeest in the entire population, though more males seemed to be taken in the Serengeti. Female zebras were taken much more than males. Tommies had much more males killed by hyenas, probobly because of their tendency to roam to patrol territories.
Age of Prey Killed
From the data, it appeared that hyenas killed slightly more younger wildbeest than what was available in the population and what lions killed. It would seem hyena coursing method of hunting would cause them to pick off stragglers in the herd, which often were younger animals.
Since zebras mature at about 3-6 years, it seems hyenas took a lot of younger ones. However, accurate estimates of the age structure of the zebra population were not available to know if they "preferred" this group, but common sense would indicate that they did.
43% of these kills were fawns (mosty less than 3 weeks old), which indicates hyenas "preferred" this group - probobly because adult gazelles are usually too fast.
Condition of Animals Caught
Unfortunately, most of the carcasses were not in condition to be examined (lots of scavengers), so marrow fat percentages (to determine nutritional condition of the animals killed) was not available. However, Kruuk strongly believed that substandard animals were being taken as the hyenas would naturally kill stragglers in a herd they were chasing. Like with wolf researchers, he couldn't tell the difference between these and other animals so these animals vulnerabilities were likely subtle.
With adult wildebeest, one or two hyenas would usually get
a herd running, the chase would last usually a few hundred meters, though sometimes as long as 5 km. During the way, often more hyenas would join in (probobly cause they sense a meal is soon). Approximately 25% of the chases had 1 hyena kill the adult wildebeest. On average 2.5 hyenas killed each adult wildebeest. The speeds were as high as 60 km/hr, but usually averaged 40-50 km/hr. When the wildbeest is caught, its attacked at the hind legs, and if multiple hyenas were present, they'd mob it, however no specific killing bites are used. The wildbeest plays the classic victim, and puts up little fight once caught and would go down in 6 minutes time on average, with quicker times being when more hyenas were present.
37% of adult wildbeest chased more than 50 m were killed, with longer chases resulting in higher success rates (< 1 km were 15% successful, > 1.5 km were 54% successful).
In contrast to wildbeest, hyenas hunting zebra always start out with a pack, which are on average 11 strong. Single hyenas are ignored by zebra groups.Typically, hyenas slowly approach the zebra group within a few meters and are often met with the aggressive stallion. Eventually, the hyenas get the zebra family moving, who pack together tightly. The chase is very slow (15-30 km/hr), and the stallion tries to attack the hyenas by kicking and biting them and the hyenas try to bite any zebra. The only other zebra that fights the hyenas is a mare who is attacking her foal. If one zebra strays from the tight group or is pulled out by the hyenas, it is attacked by all of them. Once the zebra is stopped, it puts little defense up, and is mobbed and pulled down in a manner similar to adult wildebeest.
34% of all chases of zebra (including foals) were successful.
Hyenas usually hunt both adults and fawns alone, and at high speeds. Adult tommies are killed by disemboweling, not by a killing bite. Chases of young gazelles were successful 36% of the time, and adult gazelles were caught 20% of the time.
|Canidae||Jan 9 2012, 08:18 PM Post #7|
Another of Reddhole's posts, this time on predator interaction -
Below is some information about hyena interactions with other predators, much of which will be familiar to african wildlife film aficionados.
Lions - Hyenas
Lions generally dominate, and caused 55% of hyena deaths in this study. Still, hyenas put up a respectable showing against such a formidable foe. In the Serengeti, both have overlapping diets (both mostly hunt wildbeest and zebra), although the hyena probobly takes prey a bit more selectively (more younger, older, vulnerable animals), and lions hunt very large prey occassionally (8% of the lion's diet in another study was cape buffalo). As a result, there's lots of competition between the two.
A typical encounter at a carcass:
Lions typically ignore hyenas except at kills or when harrassed by them. Hyenas will harrass lions when the hyenas are in good-sized groups. Lions may ignore them or attack them, as in the case below. However, also the hyenas may sometimes come on top, which is the second case below:
Photo of the lioness initially attacking the female hyena from the first case above:
Lions would also sometimes take a prey from hyenas as they were killing it. However, lions would usually take hyena kills after they hear the hyenas making noise. Hyenas would usually hang around, and wait for the lions to finish. Occassionally, the hyenas chase off the lion, including attacking them sometimes:
Photos of such an event:
Hyenas & Cheetahs, Hyenas & Leopards
Hyena-Cheetah is quite clear. I don't want to get into the hyena-leopard fight, the information is below, decide for yourselves!
Hyena-African Wild Dog
This is a complex interaction. Generally, hyenas would follow AWDs to get food, as the AWDs are very efficient hunters. AWDs however chased hyenas off their kills 5 times, but generally speaking, hyenas attempted to scavenge off of AWDs more. If AWDs were in small numbers, hyenas were usually successful, however, once in larger packs, their greater cohesion usually allowed them to fend the hyenas off (usually ganging up on individual hyenas and attacking the rear). Usually, an outnumbered hyena slowly approaches an AWD kill in a posture "indicating fear" and then tries to grab some scraps. Much more recent studies have been done indicating the great importance of pack size for AWDs in defending their kills from hyenas. However, sometimes there are exceptions to the numbers game for each side.
Hyenas & Jackals, Hyenas & Bat Eared Foxes
Hyenas usually ignore these, but on a rare occassion killed them or stole their kills (jackals).
Hyenas & Honey Badgers
One incident was observed where two ratels encountered a group of hyenas and chased them away a short distance while snarling.
|Canidae||Jan 9 2012, 08:20 PM Post #8|
Prey comparison of African Wild Dog, Spotted Hyena and Lion in Faro NP, Cameroon - O.P'ed by Taipan
22.214.171.124 Spotted hyenas
Only little information is available on the diet of spotted hyenas in Central and
West Africa (Di Silvestre et al. 2001). Scat analysis has been widely used to
determine food choice of spotted hyenas (Bearder 1977; Henschel & Skinner 1990;
Sillero & Gotelli 1992; Korb 2000). Quantitative data from hyena faeces is open to
a number of pitfalls, because of their scavenging behaviour and regurgitation
Spotted hyenas main prey is Buffon’s kob, maybe because kob is most
abundant (Holecamp et al. 1997). Diet of spotted hyenas is influenced by prey
availability and abundance in many areas (Henschel & Skinner 1990). Hyenas eat
a wide range of animals (Kruuk 1972). 16 prey species were found. Hyenas
consume prey from very small mammals to buffalos. Prey species found in hyena
faeces in comparable to finding in Senegal (Di Silvestre et al. 2000). Although
faecal analyses don’t give information, if the prey was killed or scavenged, it’s
highly assumed that solitary hyenas are not able to kill buffalos. Buffalo proved to
be overestimated using faecal analysis (Henschel & Skinner 1990). Hyenas
commonly hunt solitary (Holecamp et al. 1997). Individuals are often travelling
separately or in cohesive groups (Bearder 1977; Frank 1986; Sillero-Gottelli 1993;
Holecamp 1997). So the high average prey weight of 83.3 kg might result mostly
from carcasses and not from kills (Di Silvestre et al. 2000). Only few prey items of
monkeys were found because they are difficult to capture (Di Silvestre et al. 2000).
Read more: http://carnivora.proboards.com/index.cgi?board=ursidae&action=display&thread=1789#ixzz1ixOqSImk
|Canidae||Jan 9 2012, 08:21 PM Post #9|
Hyena Zebra Predation - O.P'ed by Maze & Taipan
"When hunting in small groups, the hyenas approach their prey from downwind (so their scent is not picked up by the prey) in fan formation to promote an uneven dispersal of the target prey. When the prey are dispersed in this way, it is easier for the group to spot lame individuals and to separate the young from older individuals. Zebra are the only species of prey that the spotted hyena hunts in groups. The hunting group size for zebra, however, is extraordinarily large with eleven individuals involved on average due to the difficulty of separating young from the parents and associated harem (Holekamp et al., 1997). "
|Canidae||Jan 9 2012, 08:22 PM Post #10|
Boerboels vs. Hyena, O.P'ed by ocs
|Canidae||Jan 9 2012, 08:23 PM Post #11|
Hyenas avoiding incest, O.P'ed by Dasyurus
How Hyenas Avoid Incest
By LiveScience Staff
posted: 15 August 2007 01:00 pm ET
The simple but very effective rules that female hyenas employ to prevent incest with closely related males are now known. The females go for familiar, younger males, a new study states.
The research, detailed in the Aug. 16 issue of the journal Nature, shows that a young female hyena prefers to mate with younger males in her clan—that is, males born into, or who joined, the group after she was born.
Older females also apply this rule and have an additional requirement: They prefer males that have built friendly relationships with them for several years.
The female preferences mean that most male hyenas end up leaving the group they were born into for other groups where females are less picky and more receptive.
"This is the first time a study has shown that in mammal species the system is driven by females using very simple rules to avoid breeding incestuously," said study team member Terry Burke of the University of Sheffield in the United Kingdom.
Inbreeding can be hazardous to a population because it weakens the gene pool by increasing the probability of inheriting harmful traits. Animals generally avoid inbreeding by either moving away from home or, like humans, learning who their relatives are and avoid mating with them.
|Canidae||Jan 9 2012, 08:24 PM Post #12|
Hyena courting & mating, O.P'ed by WBT -
It’s a dog’s life - aggressive male hyenas fail to impress the girls
The old adage “treat them mean keep them keen” has been turned on its head by new research published in the Royal Society’s journal Proceedings: Biological Sciences today; at least as far as hyenas are concerned.
Scientists studying Serengeti spotted hyena clans in Tanzania found that male hyenas displaying “friendly” behaviour had much more luck with the ladies than their more aggressive counterparts.
Using genetic techniques, the researchers discovered that males rarely sired offspring with females that they attempted to manipulate through monopolization or harassment, whereas males that invested time and energy in developing amicable relationships with females successfully sired offspring.
Dr Marion East, one of the authors of the study said: “What this paper reveals is the enormous amount of sexual politics among members of large hyena clans. I suspect many might think that females would choose to mate with socially dominant males. Indeed this was an assumption made by many early behavioural scientists, but our results show this is not the case with hyenas. The friendlier male hyenas are and the longer they stick around, the more favourably they are looked on by female hyenas.”
Friendly tactics included grooming, greeting and amicable gestures. Aggressive tactics were split into high and low levels of harassment. Low levels of harassment involved a male approaching a female aggressively, lunging at or biting the female or attempting to mount when the female did not cooperate. Intense harassment termed “baiting”, involved coalition of male attacking typically solitary females. None of the males that harassed females sired cubs with them.
The study revealed that female hyenas favoured males who had spent a longer time with the clan. The number of cubs sired by these males increased with tenure, with most progeny sired when they held tenures of at least four years. Males sired 10 litters on average when tenured less than 2 years and 56 when they had tenured for four or more years. The number of females with whom these males sired cubs with also increased with tenure. Males mated with eight females when tenured less than 2 years and 46 when tenured for four or more years.
Other tactics used by males in attempts to woo females included shadowing and defending. Shadowing occurred when males followed a female for weeks or, in some cases months, and defending occurred when a male prevented other males interacting with a female. Neither of these tactics conferred any advantage to hyenas using them. Males gained paternity with females that they shadowed as often as with females they did not shadow and no males sired litters with females they had defended.
In a further blow to the male psyche, research revealed that female hyena’s have developed tactics to confuse belligerent males and keep them in their place. The research indicated that males may find it difficult to determine when females are receptive and fertile, making it difficult for them to know when to coerce them. The researchers also suggested that some females mate with multiple males to confuse paternity and counter infanticide by non-sires. So although females socially dominate males, they need to employ tactics to undermine the potential advantage of males of coercion.
|Canidae||Jan 9 2012, 08:25 PM Post #13|
Hyena reproduction, O.P'ed by Taipan -
The Painful Realities of Hyena Sex
By Bjorn Carey, LiveScience Staff Writer
posted: 26 April 2006 01:00 pm ET
When a mother does her best, she expects a well-behaved child. But for top-dog hyena moms, a hell-raiser is preferred.
Alpha females give a hormone boost to their developing cubs, making them more aggressive when fighting for food and increasing their chances of survival, according to a study in the April 27 issue of the journal Nature.
The extra hormones also inspire young males to mount females early and often, giving them a better shot at performing their tricky mating dance correctly down the road.
You won't believe how hard the act is, and why.
Unlike most mammalian societies, female spotted hyenas run the show and are significantly more muscular and aggressive than males. After studying hyenas in Kenya for nearly two decades, researchers discovered that in the final stages of pregnancy, high-ranking females provide their developing offspring with higher levels of androgen-a male sex hormone associated with aggression-than lower-ranking mothers provide to their developing young.
This is the first study to show that a mother's social status, and not just her genetic makeup, can directly affect her offspring's observable physical characteristics.
Aggressiveness is a good attribute for a creature living in a society where 40 to 60 individuals scrap over food, and especially for females requiring extra energy for developing offspring.
By infusing her developing young with androgen, the mother increases the likelihood that her genetic information will survive.
'Imagine giving birth through a penis'
But providing the extra hormones takes a toll on the mother. The dose of androgen that she received from her own alpha mother damages her ovaries, making it difficult to conceive.
It also causes female reproductive organs to grow. A lot. Her clitoris, which contains the birthing canal, protrudes 7 inches from her body.
"Imagine giving birth through a penis," said study co-author Kay Holekamp of Michigan State University. "It's really weird genitalia, but it seems to work. Although giving birth through a 'penis' isn't a trivial problem."
The clitoris' birth canal is only an inch in diameter, and the tissue often tears as a 2-pound cub squeezes through the narrow opening. The rip can be fatal, as evidenced by the high death rate for first-time mothers.
Practice makes perfect
Because of the female's awkward genitalia, successful mating for hyenas is tricky to pull off. It takes careful positioning for the male to crouch behind her and somehow get his penis to point up and backwards to enter her clitoris.
"Males need practice. After a couple of months of practicing, they get it lined up just right," Holekamp told LiveScience.
Since the sons of alpha females are born hyper-aggressive, they start trying to mount females at just a few months old, giving them a better shot at sealing the deal later in life.
|Canidae||Jan 9 2012, 08:26 PM Post #14|
Hyena predation videos, O.P'ed by Reddhole -
Video of single hyena killing an adult wildebeest (not the best quality video):
Group of hyenas killing a zebra stallion with a broken leg:
|Canidae||Jan 9 2012, 08:27 PM Post #15|
Hyena attacks on people, O.P'ed by Frank -
After leopard, hyena attacks children, injures three
26 Sep 2003, 2340 hrs IST,TNN
Print Save EMail Write to Editor
VADODARA: If man-eater leopards were not enough, a hyena created panic in the Kali Pipli village in Dahod, by attacking children near a school premises on Thursday. Three persons, including a woman and her daughter, were injured in the attack.
They have been shifted to a local hospital.
Villagers killed a hyena by shooting it down with arrows, said local forest department officials. According to them, the hyena had tried to enter the school premises, which led to panic and the attack.
The children may have tried to stone the animal and instigated it. Said Vadodara circle conservator of forest H S Singh, “Because of the good monsoon in the state this year the fields are full with tall standing crop of corn and maize and provide ideal hiding places for such animals.”
Singh added that the animal may have crossed over from nearby forest areas of neighbouring Madhya Pradesh but alert teachers closed the gates and informed the police.
Some villages in the Devgadh Baria taluka of Dahod are already in a state of panic over increasing attacks by man-eating leopards who have killed about 10 people so far. Last week the forest department had one killed man-eating leopard after which another woman was killed sparking fears of more than one man-eaters operating in the region.
|Canidae||Jan 9 2012, 08:27 PM Post #16|
Young Giraffe kill, by Frank & Witleos
Edited by Canidae, Jan 9 2012, 08:47 PM.
|Canidae||Jan 9 2012, 08:28 PM Post #17|
More hyena info from Frank -
A hyena lives in a social group known as a "clan" these clans are composed of a dominant female, followed by her cubs, and the second most dominant female, followed by her cubs and so on. Although hyenas are scavengers, they also do a lot of hunting and are more kleptoparasetic then carrion eaters. Hyenas are also thought to be amazingly intelligent and they have at least eleven vocal sounds that they make, although there can be up to thirteen (still debatable). A hyena can hide meat in water for days before returning to the same spot to eat it, and memorize the indivisual identification of eighty other clan members ! There jaws are also thought to be the most powerful amongst mammalian carnivores, a hyena can bite threw a cape buffalos thigh bone as if it was a knife cutting threw butter. Females are larger then males because of there increased testosterone level, it reaches so high that females evolved there genetalia being closer to that of males (althought there chromosomes still in fact do read (x,x)) which made much more aggressive, and ultimatley gave the females more masculine features. Hyenas are also highly territorial and will kill other hyenas outside of there clan. Despite modern legend, hyenas are very aggressiev and 25 % of the cubs in a hyena litter are killed by there siblings for battles over dominance. A hyena has stomache acid with a ph of nearly 1 and can melt down pieces of pots and pans. A hyena has 34 bulky, and resistant teeth. When a hyena whoops, data collected shows that each hyena has its own indivisual whoop and a females whoop is often given more attention to then a males. Hyenas can gallop at speeds of 25-31 mph, and can run and reach a top of 37 mph. Hyenas trot at a speed of 6 mph.
|Canidae||Jan 9 2012, 08:32 PM Post #18|
Spotted Hyena (left) skull comparison with 550lb Black Bear and large male Alaskan Grey Wolf, O.P'ed by Dinocrocuta
|Canidae||Jan 9 2012, 08:33 PM Post #19|
Frank's info on Lion Predation (first section) and hyena reproduction (second section) -
Spotted hyenas are successful hunters, but they also scavenge. Their main food competitors are lions. In the Etosha National Park, Namibia hyenas are unable to prevent kleptoparasitism by lions and fail to acquire kills from lions. The reasons are the small ratio of hyenas to female and subadult lions at kills and the presence of adult male lions. Because of the hyenas' small clan sizes and large territories they seem to be unable to recruit sufficient clan members to take over lion kills or deter lions from their own kills. In Etosha, 71% of hyena mortality was due to lions; four cubs and one adult female hyena were killed by male lions during a 1-year study. Hyenas have evolved adaptations against lions and initiate aggressive interactions with lions without the immediate availability of food, which is termed mobbing behaviour. Etosha hyenas initiated mobbing attempts when lions were near the hyena's communal den. Possibly, Etosha hyenas mobbed lions to distract lions from the hyenas' den and their cubs and to warn their dependent offspring to hide from lions
Sex and the Spotted Hyena
by Robin Meadows
Face to face with the spotted hyenas in the Berkeley hills, I find it hard to believe that these are the fearsome creatures I've been reading about for weeks. Where are the bone-crushing jaws and the propensity for a pack to strip a zebra in 15 minutes flat? These hyenas are fat and friendly, and are clearly interested in their human visitors, in a nonthreatening way. When biologist Laurence Frank enters an enclosure, he is encircled by three exuberant hyenas that look for all the world like large, shaggy, undisciplined dogs in search of love. My daughters and I are equally charmed. After my initial astonishment at the hyenas' amiability, however, I realize that this reception is not at all surprising. Frank bottle-raised this trio, which means he is the closest thing to a mother they have.
In the mid-1980s, Frank and his colleague Stephen Glickman captured 20 infant spotted hyenas in Kenya and brought them home to the University of California at Berkeley. The two researchers rightly anticipated that studies of captive hyenas would unravel the mysteries of these animals, which have been famous since the time of Aristotle for being hermaphrodites.
The misconception that spotted hyenas are bisexual was perpetuated well into the twentieth century by people from Hemingway, who as a writer of fiction can be excused, to biologists, who should have known better. The truth about spotted hyenas (Crocuta crocuta) is arguably as bizarre as the myth. To the untrained eye, females look and act almost exactly like males. The two sexes' remarkable resemblance goes right down to the nitty-gritty of their genitals, which appear to be identical. Moreover, the females of this species seem to be even more masculine than the males: Females are some 10 percent larger by weight and are so much more aggressive that they dominate males in nearly every social encounter, a fact that the Disney studio paid only lip service to when developing the hyena characters for last summer's animated movie "The Lion King." While the hyenas' ringleader was indeed female, her goofy sidekick should have been named Edwina rather than Ed. The Disney studio had ample opportunity to get it right because a team of illustrators came to Berkeley to sketch Frank and Glickman's brood.
More than mere curiosities, spotted hyenas challenge the conventional wisdom of what makes us female or male and so can give us insights into the limits and latitudes of our own sexuality. Many biologists who study female-male differences let their preconceptions affect their results. For instance, while testosterone and other so-called "male" hormones are quite common in female mammals, biologists almost always focus on their estrogen and other so-called "female" hormones, notes Frank.
Despite their dog-like appearance, the three species of hyenas belong to a superfamily that includes cats, mongooses, and civets. Spotted hyenas are named for the dark brown spots that stand out against their short, brownish-yellow fur. The demented-sounding cackle they make when squabbling gives them their other common name, the laughing hyena. Spotted hyenas live in the savannas and woodlands of sub-Saharan Africa, and their range overlaps with those of the other two species of hyenas, the striped and brown hyenas (Hyaena hyaena and Parahyaena brunnea). All three species have the long necks, powerful shoulders, and short hindlegs that give hyenas their characteristic attenuated look. Likewise, all hyenas are consummate scavengers, noteworthy for being the only carnivores that can ingest a carcass in its entirety. While carnivores' digestive tracts are typically short, those of hyenas are uncommonly long and are capable of extracting nearly all the protein and fat from bones. The mineral components of bone are reduced to a fine powder that is excreted, while the hair, ligaments, and other undigestible body parts are regurgitated in a pellet.
Spotted hyenas are distinguished from their relatives in two major ways. While striped and brown hyenas supplement their diets by catching small prey from insects to foxes, these species are predominantly scavengers. In contrast, spotted hyenas hunt for most of their food and usually prey on large animals. A single spotted hyena can catch an adult wildebeest after chasing it three miles at speeds of up to 35 miles per hour.
The second major difference is, as already mentioned, that female spotted hyenas have in many ways adopted the orthodox male role. Female spotted hyenas bear, suckle, and care for their young like any female mammal. But although their genitals are clearly female in function, they are male in form. The labia are fused into what looks like a scrotum, complete with two pads of fatty tissue that resemble testes. In addition, the clitoris is elongated to the point that it is nearly the size of a male's penis and is likewise fully erectile. Astonishingly, females mate and give birth through the long, narrow canal running down the center of this "pseudopenis." During mating it retracts much like a shirt sleeve being pushed up, and during birth it stretches so much that it looks like a water balloon. "From a human perspective, the process can be thought of as giving birth through an unusually large penis," says Frank.
While highly unusual, spotted hyenas are not as anomalous as they appear to be at first glance. Rather, they are at the extreme end of a continuum of female mammals with masculine characteristics. One-quarter of mammalian families contain species in which females are larger than males, and there are other female mammals with genitals that are masculinized to some degree. For instance, spider monkeys have a large, pendulous clitoris and the European mole has an elongated penis-like clitoris.
In addition to having male-like genitals, female spotted hyenas enjoy the social position accorded to males in most mammal species: dominance. Except for when they are ready to mate, female spotted hyenas completely dominate the adult males that join their clan. (As is true of many social mammals, female hyenas stay in the clan where they were born while males disperse when they reach puberty at about two years of age.) Most tellingly, males abandon kills once females show up--Frank has seen a single juvenile female keep five full-grown males from feeding on a buffalo carcass. Males typically skirt the edges of kill sites, snatching scraps dropped by females.
Aggression is a way of life for female spotted hyenas. "Rank is inherited from mothers, and higher-ranking females teach youngsters what their rank is through aggression," says Frank. "A mother-daughter pair or two sisters will attack a subordinate when her young are around [which teaches the subordinate's young where they stand]." Dominant females threaten a subordinate by walking toward her shoulder-to-shoulder with their manes and tails raised.
While many such displays are just meant to show who's boss, subordinates sometimes sustain considerable damage. After being separated for a few hours, spotted hyenas engage in "greeting" displays that entail lifting their legs and exposing their erect pseudopenises for inspection. Subordinate females often initiate greetings and this is the only known case
of an erection being a submissive gesture. "This unusual display is not without its risks [because] each hyena puts its reproductive organs in immediate proximity to very powerful jaws," says Frank. "On the rare occasions when the aggression escalates to fighting, the resulting damage may be severe enough to destroy or seriously compromise the reproductive competence of the injured party."
The big questions about spotted hyenas are obvious. Why do the females sport such extraordinary anatomy and behavior? And why are hyenas the only mammals with females that are masculinized to such an extreme degree? Attempts to answer the first question were confounded until Frank, who coordinates the field work, and Glickman, who directs the project, established their hyena colony. Studies on the 40-odd captive hyenas are explaining the physiological basis of behaviors that Frank and his colleagues have seen in their 16-year field study of spotted hyenas in the Talek clan living in Kenya's Masai Mara National Reserve.
One of Frank and Glickman's most striking findings is that compared to males, female spotted hyenas have much higher blood levels of a steroid hormone called androstenedione, which is an androgen or classically "male" hormone. Androstenedione is particularly interesting because it can be metabolized into either the "male" hormone testosterone or the "female" hormone estrogen depending on what enzyme is present: One enzyme converts androstenedione to estrogen, while another converts it to testosterone.
Placentas typically contain both enzymes but Glickman, University of California at Berkeley endocrinologist Paul Licht, and colleagues at the University of California at San Francisco, found that the balance is skewed in spotted hyenas. Human placentas (and presumably those of most mammals) convert maternal androgens to estrogen, thus protecting female fetuses from being masculinized. Spotted hyena placentas, on the other hand, actually convert the maternal androstenedione to testosterone.
Testosterone's effect on female fetuses has been well-documented in laboratory studies. Prenatal exposure to testosterone in female rats, dogs, and monkeys causes male-like genitals as well as increased body size, aggression, and dominance--in short, the suite of characteristics found in female spotted hyenas.
However, science is just like any other part of life in that the answers are not always easy. As the pundits say, there are three kinds of logic: deductive, inductive, and "seductive," that is, plausible but not necessarily true. The third kind of logic may apply to the argument that female spotted hyenas are masculinized due to prenatal exposure to testosterone. "Everything we know about sexual differentiation is simple: Testosterone makes males," says Frank. "But because of a whole series of hints, it looks like that may not be the whole picture in spotted hyenas." One of these hints is that treatments that reduce penis size in other species--prenatal exposure to compounds that inhibit androgens, and castration before puberty--have little effect on genital size in either sex in spotted hyenas. Such findings have led the researchers to speculate that, "an as yet undiscovered novel mechanism may contribute to sexual differentiation in this species." That is, the answers are not yet in on what separates the girls from the boys.
Frank and Glickman's studies of the captive spotted hyenas have also led to the surprising discovery that they fight violently at birth. The young of predatory birds including boobies, eagles, and egrets are known to attack and ultimately kill their younger siblings soon after hatching, which may be because the second egg serves only as parental insurance in case the first fails to hatch. However, this is the first such case known in mammals. Spotted hyenas typically give birth at the mouths of abandoned aardvark burrows, which are filled with passages that narrow as they diverge from the entrance. While the burrows protect the babies from lions and other hyenas, the narrow passages also prevent the mother hyena from reaching her cubs. When ready to nurse, she lies at the entrance and makes a low, groaning sound to call her babies to the surface. After the baby hyenas have lived in the security of their burrow for a few weeks or so, their mother carries them to a communal den shared by other hyena young.
Although spotted hyenas usually have twins, observations during the first decade of the Talek clan field study showed that mothers brought many more single cubs to the communal den than expected. Instead of being mostly twins, by a few weeks of age, more than 40 percent of the litters comprised lone cubs.
What was happening during those initial weeks in the aardvark burrows where the cubs were born? Because the narrow passages make the burrows inaccessible to predators and biologists alike, Frank was unable to solve this puzzle until the first hyenas were born in the Berkeley colony. Then he saw that unlike most carnivores, which are helpless at birth, spotted hyenas are born with both the equipment and inclination to attack. Their eyes are open, their incisors and canine teeth are fully erupted, and they are able to bite within minutes of birth. And bite they do, dotting each other's shoulders and necks with tell-tale puncture wounds until dominance is established. This aggression notwithstanding, spotted hyenas don't kill their siblings directly. Rather, the subordinate sibling is so cowed by the constant attacks that it stays away from the burrow entrance and so from its mother, which means it ultimately starves to death. In the wild, as many as one-quarter of all cubs apparently die in the depths of their natal aardvark burrows.
While Frank and Glickman have made considerable progress in determining the physiological basis for the female spotted hyenas' masculinization, the answer to why spotted hyenas are the only mammals with females that are so extremely masculinized is not as clear. The generally accepted theory is that the masculinization is a consequence of the species' highly competitive communal feeding. Higher-ranking females and their young get to eat first, and the argument goes that this favors increased aggression in females, which in turn favors increased "male" hormones in females. According to this scenario, the females' masculinized genitals and intense aggression from birth are just side-effects of the increased androgens. However, Frank cautions that many other carnivores also eat together, suggesting that competition for food is not the only reason behind the female spotted hyena's masculinization. "The ancestral spotted hyenas' endocrinology must have preadapted them to this development," says Frank.
Whatever the cause, female masculinization is apparently a very successful strategy for the spotted hyena, which is the most abundant large predator in its range. But this success comes at a cost that is tremendously high for the spotted hyena--and presumably prohibitively high for other species. Notably, giving birth is difficult and dangerous, especially for first-time mothers. The fact that the pseudopenis has such a long, narrow birth canal is enough to make it a poor organ for delivering a baby. But there is the added complication that the end of the pseudopenis cannot stretch enough to accommodate passage of the baby: In a first-time mother, the baby tears its way out. "It's the only time I've ever heard hyenas cry out in pain," notes Frank.
Even worse, the umbilical cords are so short that many first-born babies die. At only six-inches long, the umbilical cord is far too short to traverse the foot-long canal down the pseudopenis, which means that either the placenta detaches or the cord breaks before the baby is born. (For comparison, in women the birth canal is only a few inches long and the umbilical cord is a generous foot and a half long.) The longer a hyena's labor, the more likely her baby is to suffocate and be stillborn--and the more likely the mother is to die. In captivity, first-time mothers labor as long as 48 hours and nearly three-quarters of first-born cubs die. Without veterinary help, many of these mothers probably would have died along with their babies; in the wild, many females die at three to four years, the age when hyenas typically first give birth.
The high rate of siblicide is another significant cost to the female spotted hyena's masculinization. Producing babies that die shortly after birth is a tremendous waste of a mother's energy. Intriguingly, female spotted hyenas have apparently managed to wring what advantage they can out of their babies' inclination to kill each other. Frank believes that mothers use siblicide to manipulate the sex ratio of their offspring.
It is well known that many female mammals bias the sex ratio of their offspring. Biologists speculate that, for example, having sons may be advantageous to bushbabies, muskrats, and other species in which daughters grow up to share territories with--and so compete for resources with--their mothers. Frank found that high-ranking females in the Talek clan generally raised more sons than daughters when the population of the clan was high. But since 1990, when about a third of the adult females left to establish a new clan, high-ranking females in the Talek clan have raised more daughters than sons.
However, while most species somehow adjust the sex ratio before their babies are born, spotted hyenas appear to adjust the sex ratio of their babies after birth. Frank has seen that in the wild, female spotted hyenas sometimes put newborn twins into separate aardvark burrows, which keeps the babies from fighting and so greatly increases the likelihood that both will survive. The implication is that mother hyenas can intervene and save their babies if they are the desired sex. Ever since they were mistaken for hermaphrodites, spotted hyenas have been among the most misunderstood species on earth. Most people follow the lead of the Disney script-writers and cast hyenas as the bad guys of the animal world for their gruesome lifestyles. But as Frank and Glickman's work shows, the qualities for which they are reviled seem to arise from a noble goal: Like any mothers, the female hyenas are just trying to provide the best for their children. As for the rest, spotted hyenas, like many of us, are largely captives of their biology.
Robin Meadows is a contributing editor to ZooGoer.
(ZooGoer 24(3) 1995. Copyright 1995 Robin Meadows. All rights reserved.)
|Canidae||Jan 9 2012, 08:34 PM Post #20|
Parasites & Spotted Hyena, O.P'ed by Frank -
|Canidae||Jan 9 2012, 08:35 PM Post #21|
Hyena foraging, O.P'ed by Taipan -
Solitary Hyenas still get the last laugh
By Greg Soltis, LiveScience Staff
posted: 17 July 2008 04:44 pm ET
Spotted hyenas lived as solitary scavengers over a million years ago. But over time, they have become more of a communal species.
New research indicates that, to offset the cost of competition among the group, spotted hyenas still demonstrate an ancestral tendency to separate themselves when searching for their next meal.
Hyenas do find some strength in numbers in several ways. They may engage in turf battles with other local hyenas. Tracking down a meal is certainly easier as a group effort – spotted hyenas are 20 percent more likely to capture prey if they have help. And this collective approach then bodes well when defending their newly acquired food from lions.
But with these advantages come drawbacks as well. Additional help before the kill translates into additional competition afterwards. And with a well-established hierarchy, the spotted hyenas higher up the ladder get their meal while others suffer.
Consequently, hyenas still head out for food but later return to their community. This cyclic process of splitting up and then reuniting, similar to humans who return home after work, is referred to as fission-fusion dynamics.
Jennifer Smith, a doctoral zoology student at Michigan State University, recently published a paper in the journal Animal Behavior that offers these results. She based her work on research performed at Masai Mara National Reserve in Kenya.
Michigan State University zoology student Brittany Gunther took this photo of a fight between a group of spotted hyenas and a lioness while taking a study abroad class at Kenya’s Masai Mara National Reserve.
|Canidae||Jan 9 2012, 08:36 PM Post #22|
Prey preference, by Reddhole -
Here is the study:
Here is the abstract:
Spotted hyaenas Crocuta crocuta were once considered mere scavengers; however,
detailed research revealed that they are very efficient predators. Information on
what spotted hyaenas actually prefer to prey on and what they avoid is lacking, as
well as the factors that influence prey selection. Data from 14 published and one
unpublished study from six countries throughout the distribution of the spotted
hyaena were used to determine which prey species were preferred and which were
avoided using Jacobs’ index. The mean of these values for each species was used as
the dependent variable in multiple regression, with prey abundance and prey body
mass as predictive variables. In stark contrast to the rest of Africa’s large predator
guild, spotted hyaenas do not preferentially prey on any species. Also surprisingly,
only buffalo, giraffe and plains zebra are significantly avoided. Spotted hyaena
most prefer prey within a body mass range of 56–182 kg, with a mode of 102 kg.
The dietary niche breadth of the spotted hyaena is similar to that of the lion Panthera
leo, and the two species have a 58.6% actual prey species overlap and a
68.8%preferred prey species overlap. These results highlight the flexible and unselective
nature of spotted hyaena predation and are probably a reason for the species’
success throughout its range, despite a large degree of dietary overlap with lions.
Here are the details on the specific prey species. Species with a small + or - next to them have enough data to be "statistically significant" (i.e. buffalo, giraffe).
|Canidae||Jan 9 2012, 08:37 PM Post #23|
Hyena hunts Baboon, O.P'ed by Taipan -
Hyena Hunts Baboon
Date: Sunday, January 25, 2004
Producer: Ronnie Watt
Jakkie Spano of Newcastle videoed a scene of a hyena hunting a baboon… and that is not a common sight! The event took place at Maroela Camp in the Kruger national Park where a troop of baboons were feeding on the fruit of a Maroela tree. A camp staff member chases them off but one female lingers behind… to her detriment. Out of the blue a lone hyena attacks her, and that’s where Jakkie’s video starts.
At first the hyena has the baboon firmly clasped by her mouth and drags it along. She is trying to free herself with her hands but it is futile. The hyena then stops and changes grip… this time it bites down on the skull in the area of the eye. The baboon offers little resistance… every now and then there is some feeble thrashing.
Of interest is that the hyena does not immediately start to feed on the baboon. Usually when in a group, hyenas will start ripping flesh as soon as prey is subdued. But this is not the case here. The baboon has formidable incisors that can inflict serious wounds and so the hyena hangs on until it is sure that its prey is incapacitated.
Again it drops the baboon… and as soon as it realises that there is still life, the hyena grasps it again firmly. It looks as though it uses its body weight to press down onto the baboon. Only after it is sure there is no life left, does it rise and carry the carcass off.
It is not often that hyenas are successful in hunting baboons. A baboon troop has a formidable defense strategy and the dominant males or lookouts will come to the rescue of any individual in distress. I am sure that the hyena’s initial firm grip on the baboon’s mouth prevented her from uttering distress calls. The subsequent vise-like grip on the skull might even have allowed the powerful teeth to penetrate the bone and damage the central nervous system.
|Canidae||Jan 9 2012, 08:37 PM Post #24|
Hyena mass, O.P'ed by Manics -
From "Mammals of southern Africa"
Males 57.8kg range=49-66.3kg
Females 64.8kg range=55.8-76.7kg
Males 62.5 range 54-70kg
Females 68.2kg range 55-81kg
Males 66.6kg range 55-79kg
Females 70kg range 56-80kg
Males 59kg range 55.8-62.5kg
Females 70.9kg Range 67.1-75kg
I didnt realise Hyenas were so large. Theres not a huge difference in size between the sexes although females are clearly larger.
The largest Male leopards were from Kruger. Older males weighed average 63.1kg and females 37.2kg.
In Zimbabwe male leopards weighed 59.7kg (52.8-71.3kg)
Females only weighed 31.5kg (28.2-34.9kg)
Its easy to see why female leopards almost never stand up to even a solitrary hyena for food. Although it emphasises how impressive this is considering the size disparity.
|Canidae||Jan 9 2012, 08:40 PM Post #25|
Prey selection by Reddhole -
Summary: This study shows that spotted hyenas hunt most of their prey in the Namib desert. It also shows that the main prey are gemsbok and mountain zebra. Old adults of both species are targeted, but young/immature animals are also likely taken frequently. Male gemsbok are targeted due to rut injuries and female mountain zebra are preferred because they are less aggressive than stallions.
Source: Tilson, Blottnitz, and Henschel; "Prey Selection by the Spotted Hyena (Crocuta crocuta) in the Namib Desert"; Madoqua Vol. 12 No. 1 P 41-49 1980
Gemsbok and Mountain Zebra Comprise the Bulk of Hyena Diet
Below is scat data. Gemsbok and zebra make up about 80% and 13% of spotted hyena diet.
The authors conclude that hyenas killed most of these animals because the prey populations were not dense (i.e. hard for hyenas to find carcasses) nor were these prey populations in extremely poor health (i.e. few carcasses available for hyenas).
Old Adult Male Gemsbok and Old Adult Female Zebra Targeted by Spotted Hyenas
Below is the age/sex predation data. Note that the authors only concluded that half of these were definite hyena kills (see extract in section below). 23 of 29 gemsbok carcasses were 12 years or older. 16 of 26 mountain zebra were 8 years or older. 65% of gemsbok carcasses were males while 69% of mountain zebra carcasses were females.
The authors explain that hyenas preferred old male gemsbok and old female mountain zebra. In addition, the authors mention that many young, immature animals are also likely killed, but carcasses are hard to locate.
Hyena Predation in the Namib Desert
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