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|Common Bottlenose Dolphin - Tursiops truncatus|
|Topic Started: Jan 9 2012, 12:27 PM (1,627 Views)|
|Taipan||Jan 9 2012, 12:27 PM Post #1|
Common Bottlenose Dolphin - Tursiops truncatus
Species: Tursiops truncatus
PHYSICAL DESCRIPTION: This is a relatively robust dolphin with a usually short and stubby beak - hence the name "bottlenose". The bottlenose dolphin (like the beluga) has more flexibility in its neck than other oceanic dolphins, because 5 of the 7 neck vertebrae are not fused together as in the other oceanic dolphins. There are 18-26 pairs of sharp, conical teeth in each side of its jaw.
COLOR: The color of the bottlenose dolphin varies considerably, but generally this dolphin is light gray to slate gray on the upper part of the body shading to lighter sides and pale, pinkish gray on the belly.
FINS AND FLUKE: The dorsal fin is high and falcate (curved) and located near the middle of the back. The flukes are broad and curved with a deep median notch. The flippers are of moderate length and pointed.
Length and Weight: Adult length is from 8-12 feet (2.5-3.8 m). These dolphins may weigh as much as 1,430 pounds (650 kg) off Great Britain, though most are much smaller in other parts of the world. Males are significantly larger than females.
Feeding: Feeding behaviors are diverse, primarily involving individual prey capture, but sometimes involving coordinated efforts to catch food, feeding in association with human fishing, and chasing fish into mudbanks. An adult bottlenose dolphin may consume 15-30 pounds (8-15 kg) of food each day. Bottlenose dolphins eat a wide variety of food, including primarily fishes, and sometimes squid, and crustaceans.
Mating and Breeding: Males reach sexual maturity at about 10 years. Females reach sexual maturity at about 5-10 years. The gestation period is 12 months. Calving can take place year-round with peaks in some areas during spring and fall. Calves nurse for over a year (12-18 months), and stay with their mothers for 3-6 years learning how to catch fish and other important tasks.
Distribution and Migration: Bottlenose dolphins are found worldwide in temperate and tropical waters, absent only from 45 degrees poleward in either hemisphere. They are frequently seen in harbors, bays, lagoons, estuaries, and river mouths. There appear to be two ecotypes: a coastal form and an offshore form. Population density appears to be higher nearshore. Biochemical studies now are providing more information about the relationship within and between the ecotypes. In some areas, dolphins have limited home ranges; in others, they are migratory. A second species Tursiops aduncus, inhabits the Indian Ocean.
Natural History: Based on a number of studies of nearshore populations, bottlenose dolphins seem to live in relatively open societies. Mother and calf bonds and some other associations may be strong, but individuals may be seen from day-to-day with a variety of different associates. Group size is often less than 20 nearshore; offshore groups of several hundred have been seen. Much of what we know of the general biology of dolphins comes from studies of bottlenose dolphins, both in captivity and in the wild.
|Taipan||Jan 11 2012, 09:41 PM Post #2|
1. Bottlenose dolphins live in groups called pods (Scott, Wells, and Irvine, 1990).
• A pod is a coherent long-term social unit.
• The size of a pod varies significantly with its composition. On the west coast of Florida, mean pod size is about seven animals (Scott, Wells, and Irvine, 1990).
• In the wild, pod composition and structure are based largely on age, sex, and reproductive condition (Wells, 1991).
° Researchers on the eastern U.S. coast commonly sight mother-calf pairs and pods of mature females with their most recent offspring (Wells, 1991).
° Subadults typically occur in mixed-sex and single-sex groups (Wells, 1991).
° Adult males are often observed alone, or in pairs or occasional trios (Wells, 1991). Adult males commonly move between female groups in their range, and may pair up with females for brief periods. Adult males rarely associate with subadult males (Wells, 1991; Herman, 1980).
2. In general, size of pods tend to increase with water depth and openness of habitat. This may be correlated with foraging strategies and protection (Shane, et al., 1986).
3. Several pods may join temporarily (for several minutes or hours) to form larger groups called herds or aggregations. Up to several hundred animals have been observed traveling in one herd (Shane, et al., 1986).
4. Researchers have identified certain factors that tend to cause a pod to either draw together or to disperse somewhat (Herman, 1980).
• Factors that tend toward cohesion include protection, fright, and familial associations.
• Factors that tend toward dispersion include alertness, aggression, and feeding.
5. There may be a social hierarchy within a group of bottlenose dolphins.
1. Dolphins in a pod appear to establish strong social bonds. Behavioral studies suggest that certain animals prefer association with each other and recognize each other after periods of separation. Field observations suggest that mother-calf bonds are long-lasting.
• Mother-calf bonds are long-lasting; a calf typically stays with its mother three to six years or more (Wells, 1991).
• Adult male pair bonds are strong and long-lasting. Male pairs often engage in a number of cooperative behaviors (Wells, 1991).
2. Bottlenose dolphins establish and maintain dominance by biting, chasing, jaw-clapping, and smacking their tails on the water (Shane, et al., 1986; Herman, 1980).
3. Dolphins often show aggression by scratching one another with their teeth, leaving superficial lacerations that soon heal (Shane, et al., 1986). Traces of light parallel stripes remain on the skin of the dolphin. These marks have been seen in virtually all species of dolphins. Dolphins also show aggression by emitting bubble clouds from their blowholes.
4. During courtship, dolphins engage in head-butting and tooth-scratching (Shane, et al., 1986).
5. Bottlenose dolphins often hunt together.
DAILY ACTIVITY CYCLES
1. Observations indicate that dolphins undergo daily cycles of activity.
2. Bottlenose dolphins are active to some degree both day and night (Shane, et al., 1986).
3. Social behavior comprises a major portion of bottlenose dolphins'daily activities (Shane, et al., 1986).
4. Feeding usually peaks in the early morning and late afternoon (Shane, et al., 1986).
1. Dolphins frequently ride on the bow waves or the stern wakes of boats. This is probably adapted from the natural behavior of riding ocean swells, the wakes of large whales, or a mother dolphin's "slip stream" (hydrodynamic wake) (Shane, et al., 1986).
2. Dolphins have been seen jumping as high as 4.9 m (16 ft.) from the surface of the water and landing on their backs or sides, in a behavior called a breach.
3. Both young and old dolphins chase one another, carry objects around, toss seaweed to one another, and use objects to solicit interaction. Such activity may be practice for catching food.
PROTECTION & CARE
1. Large adult males often roam the periphery of a pod, and may afford some protection against predators (Herman, 1980).
2. Researchers have observed scouting behavior in bottlenose dolphins. An individual may investigate novel objects or unfamiliar territories and "report" back to the pod (Herman, 1980).
3. Bottlenose dolphins may aid ill or injured pod mates. They may stand by and vocalize, or they may physically support the animal at the surface so it can breathe.
|Taipan||Jan 11 2012, 09:41 PM Post #3|
b]Dolphins ‘know each other’s names’
Whistles are used for individual recognition[/b]
research showing they communicate by whistling out their own “names”.
The evidence suggests dolphins share the human ability to recognise themselves and other members of the same species as individuals with separate identities. The research, on wild bottlenose dolphins, will lead to a reassessment of their intelligence and social complexity, raising moral questions over how they should be treated.
The research was carried out by Vincent Janik of the Sea Mammal Research Unit at St Andrews University, who has found bottlenose dolphins to be among the animal world’s quickest learners of new sounds.
He said: “Each animal develops an individually distinctive signature whistle in the first few months of its life, which appears to be used in individual recognition.”
The research has its origin in the 1960s when dolphin trainers first noticed that captive animals each had their own personal repertoire of whistles.
This prompted speculation that dolphins had their own language and might even have individual “names”. However, the theory was controversial among whale and dolphin researchers, and until now, there had been no means of testing it.
Janik’s work was based on a group of dolphins living in Sarasota Bay, Florida, who have been studied for more than 30 years. Over that time researchers have built up a detailed picture of individual dolphins, their family ties and their “social” interaction.
They have also made extensive recordings of the noises made by individual dolphins and isolated the sounds thought to be their “signature whistles” or names.
In the study some of the Sarasota Bay animals were corralled in a net. The researchers then played synthetic versions of the signature whistles of other dolphins through underwater loudspeakers to see if they would evoke a response in the captive animals. The use of synthetic whistles ruled out the possibility that the animals might simply be recognising the sound of each other’s voices.
They found that dolphins responded strongly to the whistles of their relatives and associates while generally ignoring those of dolphins to whom they had no link.
Janik said: “Bottlenose dolphins are the only animals other than humans to have been shown to transmit identity information independent of the caller’s voice.”
The findings are supported by other authorities. Denise Herzing, research director at the Wild Dolphin Project at Florida Atlantic University, said it was already clear that many of the 77 known cetacean (whale and dolphin) species had rudimentary languages.
“We know that dolphins’ brains are nearly as large and complex, relative to body size, as those of humans. They have evolved to be intelligent and that implies being able to communicate,” she said.
Dolphins may, however, be just the first of many species where individuals are found to have their own names. Other researchers have already found evidence for highly developed language skills in parrots, crows and primates.
Great apes, such as chimpanzees and orang-utans, have been a popular subject for research because they are so closely related to humans.
Their limited vocal apparatus means they cannot speak but researchers at Georgia State University have taught chimpanzees to communicate in English via computers equipped with customised keyboards and voice synthesizers.
The African grey parrot is another renowned linguist, able not only to learn words but to use them in the right context.
Even some rodent species may have developed a rudimentary language. Con Slobodchikoff of Northern Arizona University recently found that prairie dogs, a large rodent found in the western United States, shared a language of at least 100 words.
Donald Broom, professor of animal welfare at Cambridge University, said species living in large groups all had advanced communication skills. “They have a complex social structure where they have to live with others, negotiate friendships and find mates. If dolphins are using names I expect we will find the same in other species with similar lifestyles.”
|Taipan||Jan 11 2012, 09:42 PM Post #4|
Some Bottlenose Dolphins Don't Coerce Females To Mate
ScienceDaily (Apr. 9, 2007) — Mating strategies are straightforward in bottlenose dolphins, or are they? Much of the work carried on male-female relationships in that species to date show that males tend to coerce females who are left with little choice about with whom to mate.
This explains the complex relationships we observe in male bottlenose dolphins, which are only paralleled by human social strategies: the formation of alliances and alliances of alliances, also called coalitions. These alliances and coalitions are then used to out-compete other male bands to access females.
A population of bottlenose dolphins in Fiordland, New Zealand, may be rewriting the textbooks. In this population males form alliances and coalitions and have complex social relationships, but they do not coerce females into mating.
David Lusseau, in a study published this week in PLoS ONE, posits that the complexity of male social relationships in this population emerge to compete for female choice. Male coalition formation is observed during fights in this population. Usually coalition formation will be driven by short-term gains for the helper (for example access to females). But there do not appear to be any short-term benefits in coalition and alliance formation in this population. Instead one male band seems to spend much more time with sexually receptive females and females with new calves than others.
Lusseau says: "In a mating system driven by female selection being able to exclude other males from the vicinity of oestrus females means that individuals can be more readily picked as a favourite partner."
The old saying seems to hold true for these dolphins: "far from the eyes, far from the heart."
Two bottlenose dolphin males butt heads in Doubtful Sound, New Zealand.
Citation: Lusseau D (2007) Why Are Male Social Relationships Complex in the Doubtful Sound Bottlenose Dolphin Population?. PLoS ONE 2(4): e348. doi:10.1371/journal.pone.0000348 (http://dx.doi.org/10.1371/journal.pone.0000348)
Adapted from materials provided by Public Library of Science, via EurekAlert!, a service of AAAS.
|Taipan||Jan 11 2012, 09:42 PM Post #5|
Dolphin rescues stranded NZ whales
Posted 4 hours 4 minutes ago
Updated 3 hours 9 minutes ago
A dolphin has guided two stranded whales to safety after human attempts to keep the animals off a New Zealand beach failed, a conservation official said.
"I've never heard of anything like this before, it was amazing," Conservation Department officer Malcolm Smith said.
The actions of the dolphin, known for playing with people in the water at Mahia Beach on the east coast of the North Island, probably meant the difference between life and death for the whales, he said.
Mr Smith had been working for over an hour-and-a-half to save the two pygmy sperm whales, which had repeatedly become stranded despite his attempts to push them back out to sea.
A dolphin, named Moko by locals, appeared and guided the whales to safety after apparently communicating with them, he said.
The whales, a three-metre female and her 1.5-metre male calf, were apparently confused by a sandbar just off the beach and could not find their way back to open water.
Mr Smith had been alerted at daybreak by a neighbour about the two stranded whales on Mahia Beach near his home.
"Over the next hour and a half I pushed them back out to sea two or three times and they were very reluctant to move offshore," he said.
"I was starting to get cold and wet and they were becoming tired. I was reaching the stage where I was thinking it's about time to give up here, I've done as much as I can."
In that situation, whales are often humanely killed to end their suffering.
Moko to the rescue
Mr Smith said Moko arrived on the scene and he could hear the whales and the dolphin making noises, apparently to one another.
"The whales made contact with the dolphin and she basically escorted them about 200 metres parallel with the beach to the edge of the sandbar," he said.
"Then she did a right-angle turn through quite a narrow channel and escorted them out to sea and we haven't seen those whales since.
"What the communication was I do not know, and I was not aware dolphins could communicate with pygmy sperm whales, but something happened that allowed Moko to guide those two whales to safety."
Soon after, Moko was seen playing with swimmers on Mahia Beach, one of her favourite activities since she took up residence at the beach nearly a year ago.
The two-metre bottlenose dolphin has become well known for her antics at Mahia, which include playing in the surf with swimmers, approaching boats to be patted and pushing kayaks through the water with her snout.
"She likes people with flippers on, she's attracted to them, she's attracted to kayaks and boogy boards as well, and that'll keep her occupied for some time," Mr Smith said.
Such close interaction with humans is very rare among dolphins but not unknown.
"She's become isolated from her pod obviously for one reason or another, but obviously made Mahia home just at the moment."
Mahia gets up to 30 whale strandings a year, most of which end with the whales having to be put down.
"I don't know if next time we have a whale stranding we can get her to come in again. She certainly saved the day for us and the whales this time."
A dolphin guided the whales to safety after apparently communicating with them. (File photo) (AAP: Dave Hunt)
Video : Moko the Dolphin
|Taipan||Jan 11 2012, 09:43 PM Post #6|
Adelaide dolphins learn to ‘Tailwalk’
Wave tailwalking in the Port River, near Adelaide.
August 2008. A wild dolphin in Adelaide has been teaching other wild dolphins the art of ‘tailwalking', a behaviour which is extremely rare in the wild but is a trick much loved by dolphinarium trainers all over the world.
Scientists from WDCS have been stunned to witness a number of dolphins from a group living in the waters off Port Adelaide performing the trick, which is usually only seen in captivity, when dolphins have been trained to entertain the public by surging vertically out of the water and then propelling themselves backwards while remaining almost fully upright in the air, ‘walking' through the water.
Probably learned in captivity
It would appear that Billie, a female bottlenose dolphin, picked up this odd behaviour during a short time in captivity almost 20 years ago. In the early 1980s Billie became trapped behind a marina lock and, unable to return to the sea, she was captured by the local dolphinarium. Billie was kept in a concrete tank for three weeks before being released back into the wild, with a ‘3' branded on her dorsal fin to make her easily recognisable.
Despite receiving no formal training during this time, it would appear that Billie observed her cell mates being fed for performing tailwalking tricks, and learned the behaviour for herself. After she was released from the dolphinarium, Billie returned to her usual haunts and it is believed that she has passed on the skills she acquired during her captivity.
Dr Mike Bossley, of WDCS Australia said: "I have observed all the local dolphins over a number of years, and have watched Billie occasionally performing tailwalks in the years since her release, sometimes in the bow wave of large ships, which is an awesome sight!
Three ‘tailwalking' dolphins
"About five years ago another female dolphin called Wave began performing the same behaviour, but does so with much greater regularity than Billie. A third adult female dolphin has also been seen tailwalking."
It is not known why the Adelaide dolphins have begun performing this behaviour, although observations are now being carried out to determine whether the behaviour might be a form of play or communication, and also to find out whether other members of the dolphin group will inherit the tailwalking skills.
Dr Mike Bossley commented: "Irrespective of function, it would seem that tail walking in the Adelaide waters is another example of cultural behaviour in large brained animals. By cultural behaviour we mean a behaviour that is transmitted between individuals and becomes a characteristic of a particular social group."
Cultural behaviour in animals
The most famous example of this is Jane Goodall's discovery that apes used twigs to capture termites in the Gombe Stream reserve, and more recently examples have been found in dolphins, including a small group of dolphins in Western Australia which hold sponges over their noses as they search for spiny fish on the ocean floor.
Dr Mike Bossley added: "If tailwalking is a true cultural behaviour, it will gradually spread through the local population, probably by being adopted by youngsters. WDCS will maintain its quiet, non invasive observations of these enigmatic animals and continue to document the behaviour of these wild, free dolphins."
Cathy Williamson, Anti-captivity Campaigner for WDCS said: "This behaviour by the Adelaide dolphins demonstrates their intelligence and is even more proof that these animals are unsuitable for confinement in captivity, where they are unable to express natural behaviour or form normal social groups with other animals."
Billie and Wave are both part of WDCS's adopt-a-dolphin program - www.adoptadolphin.com.au
|Taipan||Jan 11 2012, 09:43 PM Post #7|
Dolphin "Chef" Follows Cuttlefish Recipe
National Geographic News
January 28, 2009
A wild dolphin has been observed following a specific recipe for preparing a mollusk meal, even stripping the animal of its internal shell and beating it free of ink, a new study says.
The female Indo-Pacific bottlenose dolphin was seen repeatedly catching, killing, and preparing giant cuttlefish, which are relatives of octopuses and squid.
The creatures spawn in huge numbers in South Australia's Upper Spencer Gulf.
"It's an example of quite sophisticated behavior," said study co-author Tom Tregenza, a research fellow at the University of Exeter.
Despite their lack of limbs, dolphins have developed clever ways to use their snouts, Tregenza noted.
"A dolphin is like a genius trapped in the body of a fish."
In 2003 and 2007, the same dolphin (identified by the circular scars on its head) was filmed underwater prepping its meal by researchers Mark Norman and Julian Finn of Museum Victoria in Melbourne, Australia.
The female herded a cuttlefish to the seafloor, pinned it with her snout, and thrusted downward, breaking the cuttlefish's internal shell, or cuttlebone, and instantly killing it.
The dolphin then raised the dead body into the water and beat it with her snout, draining its ink.
Next the prey was returned to the seafloor, where the dolphin scraped it along the sand to strip off its bone.
Ink is difficult to digest and is generally unpleasant to the dolphin, Tregenza said, and the bone is not nutritious.
Such a complex series of behaviors are unusual among mammals, especially marine mammals, said Tregenza, whose research appeared January 21 in the journal PLoS One.
The skills are particularly advanced, he added, because the reward only comes at the end—the dolphin did not get a treat at the end of each step as it would have were it trained.
The study team observed behaviors of dolphin pods above-water in the Australian gulf that suggest such culinary prowess is widespread among that population.
For example, the team found intact, clean cuttlebones at the ocean's surface when pods of dolphins passed through.
Now, a "fascinating" question is whether the behaviors are learned, Tregenza said.
If the behavior is passed on, as is seen with sponge-tool use in Shark Bay, Australia, for instance, this gives the animal "an amazing amount of flexibility," Tregenza said.
Learned behavior "can bring the power of multiple generations to bear on a particular problem," he said, as opposed to a single individual inventing the process from scratch in its lifetime.
Stefanie Gazda, a dolphin researcher at the University of Massachusetts Dartmouth, researches how dolphins divide labor in Cedar Key, Florida.
The finding that several members of the Australian dolphin pod seem to be cuttlefish chefs "lends credence to the idea that the behavior is learned," Gazda said in an email. She has received funding from the National Geographic Society, which owns National Geographic News.
"This interesting behavior adds to the literature on the extensive variations on foraging strategies found in bottlenose dolphins," she added.
A wild dolphin in Australia has been observed following a set of steps to prepare a mollusk, a new study says.
The dolphin pinned the cuttlefish to the seafloor (top left), lifted it toward the surface (top right), beat it with her snout to release ink (bottom left), stripped it of its internal shell, and then consumed the animal whole (bottom right).
|Taipan||Jan 11 2012, 09:44 PM Post #8|
Dolphins Maintain Round-the-clock Visual Vigilance
ScienceDaily (May 1, 2009) — Dolphins have a clever trick for overcoming sleep deprivation. Sam Ridgway from the US Navy Marine Mammal Program explains that they are able to send half of their brains to sleep while the other half remains conscious. What is more, the mammals seem to be able to remain continually vigilant for sounds for days on end. All of this made Ridgway and his colleagues from San Diego and Tel Aviv wonder whether the dolphins' unrelenting auditory vigilance tired them and took a toll on the animals' other senses?
Ridgway and his team set about testing two dolphins' acoustic and visual vigilance over a 5 day period to find out how well they functioned after days without a break.
First Ridgway and his colleagues, Mandy Keogh, Mark Todd and Tricia Kamolnick, trained two dolphins to respond to a 1.5 s beep sounded randomly against a background of 0.5 s beeps every 30 s. Ridgway explains that the sounds were low enough for the dolphins to barely notice them as they swam through their enclosure, but the animals sprung into action every time they heard the 1.5 s tone, even after listening to the sounds for 5 days without a break. Their auditory vigilance remained as sharp as it had been 5 days earlier.
Next Allen Goldblatt and Don Carder designed a visual stimulus to test the dolphins' vigilance while they continued listening to the repetitive beeps. Knowing that the dolphins' binocular vision is limited because their eyes are situated on opposite sides of their heads, Kamolnick trained one of the dolphins, SAY, to recognise two shapes (either three horizontal red bars or one vertical green bar) with her right eye before training her to recognise the same shapes with the left eye, reasoning that if half of her brain was asleep during testing, the dolphin would only see the shapes through the eye connected to the conscious half of the brain.
But the team were in for a surprise when they began training SAY's left eye. She already recognised the shapes, even though her left eye had not seen them previously. Ridgway explains that the information must be transferred between the two brain hemispheres and suspects that the dolphin's inter-hemispheric commissures, which connects the two halves, may transfer the visual information.
Having trained both dolphins to recognise the shapes, the hard part began: monitoring and rewarding the dolphins continually over a 5 day period while the team tested the animals' responses to both the sound and visual stimuli. Amazingly, even after 5 days of listening out for 1.5 s beeps amongst the 0.5 s beep background, the dolphins were still responding as accurately as they had done at the beginning of the experiment.
The team also enticed the dolphins into a bay at night where they could be shown the horizontal and vertical bar shapes, and found that the dolphins were as sharp at the end of the 120 hour experiment as they had been at the beginning. And when the team checked the dolphins' blood for physical signs of sleep deprivation, they couldn't find any. After 5 days of unbroken vigilance the dolphins were in much better shape than the scientists.
1.Ridgway, S., Keogh, M., Carder, D., Finneran, J., Kamolnick, T., Todd, M. and Goldblatt, A. Dolphins maintain cognitive performance during 72 to 120 hours of continuous auditory vigilance. Journal Of Experimental Biology, 212, 1519-1527
|Taipan||Jan 11 2012, 09:44 PM Post #9|
Dolphins Use Diplomacy in Their Communication, Biologists Find
ScienceDaily (June 9, 2010) — A Spanish researcher and a Paraguayan scientist have presented the most complete and detailed European study into the repertoire of sounds used by bottlenose dolphins (Tursiops truncatus) to communicate. The study reveals the complexity and our lack of understanding about the communication of these marine mammals.
Until now, the scientific community had thought that whistles were the main sounds made by these mammals, and were unaware of the importance and use of burst-pulsed sounds. Researchers from the Bottlenose Dolphin Research Institute (BDRI), based in Sardinia (Italy) have now shown that these sounds are vital to the animals' social life and mirror their behaviour.
"Burst-pulsed sounds are used in the life of bottlenose dolphins to socialise and maintain their position in the social hierarchy in order to prevent physical conflict, and this also represents a significant energy saving," Bruno Díaz, lead author of the study and a researcher at the BDRI, which he also manages, said.
The study, published by the publishing house Nova Science Publishers in the book Dolphins: Anatomy, Behaviour and Threats, presents the most complete repertoire ever of these burst-pulsed sounds and whistles, gathered using bioacoustics since 2005 in the waters off Sardinia (Italy).
According to the experts, the tonal whistle sounds (the most melodious ones) allow dolphins to stay in contact with each other (above all mothers and offspring), and to coordinate hunting strategies. The burst-pulsed sounds (which are more complex and varied than the whistles) are used "to avoid physical aggression in situations of high excitement, such as when they are competing for the same piece of food, for example," explains Díaz.
Sounds that mark out hierarchies
According to Díaz, bottlenose dolphins make longer burst-pulsed sounds when they are hunting and at times of high aggression: "These are what can be heard best and over the longest period of time," and make it possible for each individual to maintain its position in the hierarchy.
The dolphins emit these strident sounds when in the presence of other individuals moving towards the same prey. The "least dominant" one soon moves away in order to avoid confrontation. "The surprising thing about these sounds is that they have a high level of uni-directionality, unlike human sounds. One dolphin can send a sound to another that it sees as a competitor, and this one clearly knows it is being addressed," explains the Spanish scientist.
New research presents the most complete repertoire ever of burst-pulsed sounds and whistles made by dolphins, gathered using bioacoustics.
|Taipan||Jan 11 2012, 09:45 PM Post #10|
|Taipan||Jan 11 2012, 09:45 PM Post #11|
|Taipan||Mar 28 2012, 05:47 PM Post #12|
Bottlenose dolphins: 'Gangs' run society, scientists say
By Victoria Gill Science reporter, BBC Nature
28 March 2012 Last updated at 01:33
Male dolphins in Shark Bay, Australia Bonded male dolphins mimic each other's behaviour
Male bottlenose dolphins organise gang-like alliances - guarding females against other groups and occasionally "changing sides".
A team studying dolphins in Shark Bay, western Australia, say the animals roam hundreds of square kilometres, often encountering other dolphin groups.
The researchers observed the dolphins there over a five-year period, recording their movements.
They report their findings in the Royal Society journal Proceedings B.
Dr Richard Connor, a researcher from the US who took part in this study, first began his studies of the Shark Bay dolphins in the early 1980s.
This latest study reveals that these highly intelligent marine mammals live in an "open society". Rather than males guarding a specific territory, groups have what Dr Connor described as a "mosaic of overlapping ranges".
The fact that the dolphins travel in their troops and frequently encounter strangers reveals a great deal about their intelligence, because when one group meets another, the animals have to decide how to respond.
Shark Bay dolphins deal with this by organising themselves into three different types of alliances.
The first is pairs or trios that work together to capture and herd fertile females. "These consortships can last over a month," Dr Connor explained.
In a "second-order alliance", the animals form "teams" of between four and 14 males which mount attacks on other groups to take their females, or to defend against attacks.
In a third level, the dolphins have "friendly relations" between these larger teams; they join forces to form larger dolphin armies, working together to defend their females against other large, aggressive groups.
Only humans and Shark Bay dolphins have multiple levels of social groups
Dr Connor explained to BBC Nature that animals need to be "incredibly smart" to operate in this type of society, where they often encountered other unfamiliar animals and had to work out whether they were a threat or an ally.
"The leading idea for the evolution of really large brains is that it was driven by complex social relationships," he told BBC Nature.
So rather than an encounter with another group of dolphins automatically resulting in "us against them" aggression, Shark Bay dolphins decide when to use friendly behaviour in order to make allies, and can even "switch sides".
Only humans and the Shark Bay bottlenose are known to have these multiple levels of male alliances in their social network.
Dr Nichola Quick, a researcher at the University of St Andrews' Sea Mammal Research Unit, told BBC Nature that understanding how animals managed social interactions in the wild was crucial in order to "truly understand their behaviour".
"If, for example, we are interested in impacts of [human] activity on animals," she said, "we can only really tell if an impact has occurred if we know what the animals 'normally' do."
|Taipan||Jun 27 2012, 08:31 PM Post #13|
Dolphin Genes Hold Clues to Animal Intelligence
Jennifer Welsh, LiveScience Staff Writer
Date: 26 June 2012 Time: 07:01 PM ET
Two bottlenose dolphins put on an acrobatic show.
Evolution-wise, bottlenose dolphins have left their mammalian brothers in the dust, and new research is showing what genes they changed to do it. These genes include those involved in brain and metabolism.
These changes could be why dolphins are known to be exceptionally smart, able to use tools, recognize themselves and even communicate with each other and with trainers.
"We are interested in what makes a big brain from a molecular perspective," study researcher Michael McGowen, of Wayne State University School of Medicine in Michigan, told LiveSCience. "We decided to look at genes in the dolphin genome to see if there are similarities in the genes that have changed on the dolphin lineage and those that have changed on the primate lineage."
The researchers compared about 10,000 genes from the bottlenose dolphin with nine other animals. (These included the cow, horse, dog, mouse, human, elephant, opossum, platypus and chicken — cows being the dolphin's closest relatives with a sequenced genome.)
By studying its mutations, they pinpointed which genes were "evolving" or what scientists call "being selected for" — genes that underwent changes and were passed on to future generations of dolphins — by comparing them to the analogous genes from the other species. If a dolphin gene has more protein-changing mutations than the cow version, for instance, that means it was actively evolving in the dolphin population at some time.
More than 200 of the genes in their survey were drastically changed in the dolphins. Twenty-seven of these were involved in the nervous system (like the brain and sensory organs). There were also many changes in the genes related to metabolism (similar to changes seen in primates), which McGowen said are important because, "brain tissue uses much more energy than other tissues."
While we know these genes are associated with the brain, and this study says the genes are different in smarter animals, the researchers caution against linking them directly. Differences in the gene's "code" doesn't mean the gene actually acts any differently in the animal.
"We may not know exactly what they do yet even in humans or mice (the two most well-characterized mammals from a genetic perspective), much less dolphins; however, their function in the brain points to their importance," McGowen said. "Probably, changes in these genes could have led to the amazing cognitive capacity seen in dolphins — it definitely points in that direction."
Unexpectedly, the researchers also saw that the dolphins were evolving more slowly than some of the other animals, a trait also seen in other mammals with big brains.
"Over time (since the split between dolphins and cows about 70 million years ago), we observe many more mutations or changes in the DNA along the cow branch (and indeed horse and dog branches) than we do along the dolphin branch," McGowen told LiveScience in an email. "This is exactly what we see in primates and elephants."
This is probably because these animals are using a different life-history approach — investing more in their offspring, but having fewer babies — which leads to slower evolution.
"It is striking that we see such similar molecular rates between all of these lineages and they have all such comparative large brains," McGowen said of the dolphins and primates.
The research is detailed in the June 27 issue of the journal Proceedings of the Royal Society B: Biological Sciences.
|Sam1||Jul 19 2012, 06:00 AM Post #14|
THE DRAMA OF MOTHER DOLPHIN AND HER MORTALLY INJURED CALF
|Sam1||Jul 19 2012, 06:05 AM Post #15|
Highly advanced mathematical abilities?
"Dolphins may use complex nonlinear
mathematics when hunting, according to a new
study that suggests these brainy marine
mammals could be far more skilled at math than
was ever thought possible before."
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