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| Brown Bear - Ursus arctos | |
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| Tweet Topic Started: Jan 7 2012, 08:00 PM (28,286 Views) | |
| Canidae | Dec 29 2012, 03:09 AM Post #31 |
Omnivore
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Ursus, thanks for posting all this, and sorry for my late reply! I also brought some stuff you posted in the 'Grappling dilemma' thread on bear predation and how it can vary with region, as predation is afterall a part of diet, but sorry if I am hijacking the thread in some way! "A Day in the Life of an Alaska Brown Bear By Riley Woodford In the film “Being John Malkovich,” a mysterious portal allows people to pop into the head of actor John Malkovich and spend a few minutes seeing the world through his eyes. In the video “A Bear’s Eye View: A Day in the Life of a Bear,” footage from a collar-mounted camera allows people to see the world from the neck of a 700-pound Alaska brown bear. Like the Spike Jonze film, the subject is unaware he’s hosting “passengers.” I’ve watched “A Day in the Life” seven or eight times and every time I notice some new, fascinating detail. I’ll highlight some of those details, and provide some insights into what is happening. Read this, then watch the video. The link is at the end of the article. Wildlife biologist Chris Brockman assembled the 13-minute video from more than 100 separate 20-second snippets, all recorded on May 26 by one bear. The collar camera recorded a 20 second clip (with audio) every 15 minutes. A GPS location was also recorded, and researchers will be able to create a map that reflects the bear’s travels. This will offer further insights - in some cases the bear is revisiting sites where he’s found food, or left kills. The bear is Boar 6041, a 10-year old male brown bear in the Copper River Basin of Southcentral Alaska. He’s part of a study called the Nelchina Brown Bear project. (Alaskans tend to use the terms brown bear and grizzly bear interchangeably). Alaska Department of Fish and Game researchers equipped this bear with a VHF radio collar in the spring of 2007, and he’s been located 66 times over the past years. He was equipped with the collar camera in mid-May, 2011, and it was retrieved about one month later. State wildlife biologist Becky Schwanke is leading the Nelchina Brown Bear project, and she’s been keeping tabs on Boar 6041 since 2007. She said his home range is roughly 44 miles east to west and 33 miles north to south. “He knows his home range in and out and he’s successful,” she said. “I suspect he has a circuit through his home range, and that’s what he does this time of year, the same pattern.” The camera sits below his chin, and sometimes slides around on his neck giving a cock-eyed view. Usually, his chin is visible and often his mouth. A counter at the bottom left of the frame gives the date and time. It’s bear time, starting at midnight. The day is May 26. It’s close to the summer solstice in Southcentral Alaska, nights are short and days are long. A beautiful, sunny day dawns clear, but we don’t see that at first because the bear is sleeping on the camera. To reduce the video file to a manageable size and highlight activity, several edits were made. The bear is wakes up at 3:17 am, so that's where we begin his day. 3:32 a.m. he’s breeding with a female bear, and at 4:02 there’s a good view of her ear and head. Later in the day he’ll mate again with a different female. 4:32 a.m. he’s up and walking. 4:47 is breakfast time. He’s eating a pile of fish by a lake, presumably winter-killed. Another short clip (also available for viewing as part of this collection) made a day earlier shows him eating from this same pile of fish, so it seems he found this resource earlier, ate some, and has returned. 5:02 he’s pawing at the water, perhaps pulling some submerged fish carcasses up to shore. He then goes back to eating the beached fish. He’s still eating fish at 5:17, but then lays down for a rest. The collar camera was programmed to turn off for a set period each day to extend the total duration of camera life, and the camera goes off at 6 am and comes on again at noon. The next clip is noon. He’s walking quickly, and it soon becomes apparent he’s following another bear. He’s still following the bear at 12:15, but in the next clip at 12:30 there’s no sign of the other bear. The audio is slightly out of synch with the counter, we hear water gurgling at 12:30 but he’s not in the water until the next clip at 12:45. Those images are interesting - he’s not just drinking but seems to have his head underwater. He’s cruising again at 1 pm (13:00), and you see a few water drops on the lens. At 1:15 he stands up and looks skyward, the lens is dry. At 1:45 (13:45) there is brief glimpse of an animal lying on the ground, but it’s difficult to identify it. At 3:00 he’s eating a dead moose, it looks like an adult. He’s still eating at 3:15, but by 3:30 he’s moving again. A drop of blood creates a red spot on the lens. At 3:45 he’s breeding with a different sow, she has a red ear tag. She’s one of about 22 bears marked in the Nelchina Brown Bear Project, but she’s not a camera collared bear. (Other camera footage recorded a few weeks later in June indicates this boar killed and ate another of the study bears, a 6-year old female). He’s on the move again at 4:15, and stops to investigate a pile of bear scat. At 5:15 pm he’s eating again, looks like an adult moose. This winter, as researchers are able to correlate GPS data with the collar camera images, they can determine if he’s returned to the earlier carcass or discovered another. He sits down at 5:45 and rests for about five hours. This section has been edited out. He's active again at 10:16 (22:16) so we pick up there. At 10:31 he approaches another bear. We glimpse the red ear tag, it’s likely that same female. If there is any further interaction, we don’t see it, at 10:45 he’s on the move again. At 11 p.m. he’s eating again. He’s still eating at 11:15. It’s difficult to tell what he’s eating. At 11:31 he’s bedded down, and the light is fading. At 11:45 something seems to be moving at the bottom right edge of the frame, it looks like he may be bedded down near another bear. “Bear’s Eye View: A Day in the Life of a Bear” offers insights into this bear’s behavior in late spring. Behavior varies between bears, some are better hunters, others more omnivorous, and behavior also changes throughout the year." From here. Collar-cam videos provide grizzly bear's view of Alaska Grizzly Boar 6041 had a busy day on May 26. The 700-pound, 10-year-old Alaska bear woke up at 3:17 a.m. as the sun peeked out beneath gray skies. Within 15 minutes, he was attempting to impregnate a willing sow. Then it was off to eat fish, swim, rip meat off a moose carcass, attempt more bear sex with a different female and walk for miles over tundra. The Alaska Department of Fish and Game knows this because it's recorded on video. The department this week released a 13-minute compilation of 20-second clips taken by a prototype video camera mounted on a collar placed on Boar 6041, part of a study of bear behavior on the east side of the Talkeetna Mountains. Division of Wildlife regional supervisor Bruce Dale watched clips from the pilot video program and found it hard to pull away. "When you flipped it on, there would be a bear, and it would be basically on a march, just lined out, busting through the brush, not ambling around the trail and stopping to sniff the flowers. This bear was going somewhere," Dale said. "And then your 10 seconds are up. So you really want to click on the next one to find out where that doggone bear is going." The department spelled out the video program in its online monthly magazine, Alaska Fish and Game News. Collars were placed on bears as part of a study of bears' effect on the moose population, and the effect of liberalized hunting on bears. Up to 85 percent of moose calves in the study area do not live to autumn. Most are killed by grizzlies, according to the department. However, some bears have never been detected at kill sites when tracked with traditional satellite collars. Biologists want to find out if they have another source of protein, and whether less predatory behavior has an effect on body size, condition, and offspring, Dale said. In the pilot project, biologists put camera collars on four bears known to prey on ungulates: the boar, a lone sow, and two sows with single cubs. The cameras on the sows with cubs eventually failed, likely damaged by the youngsters wrestling with their mothers. The cameras recorded nearly 12,000 segments over a month. Biologists are matching footage to GPS data. Videos from three bears were recorded in 10-second segments. The department posted nine clips showing bears playing, swimming, eating and meeting other bears. Boar 6041 wore a camera that recorded 20-second clips. Fitted with a collar in spring 2007, he has a range of about 44 miles east to west and 33 miles north to south. Over the month with the video collar, he bred with at least three sows and racked up a number of kills -- moose and caribou calves, a hare, a beaver and another adult bear. The 13-minute clip was taken from 100 separate videos shot May 26. After his early-morning romance, he made his way to a lake to gorge on winter-kill fish, then pawed at the water, possibly pulling up submerged carcasses. The camera was off from 6 a.m. to noon, but when it switched on, he went for a swim in an icy lake. At 3 p.m., he fed off a moose carcass. He bred again 45 minutes later. For all of the boar's promiscuity, however, there's not much to the mating scenes in a short clip. It's more like bear nuzzling. At 4:15, he stopped to sniff bear scat. A half hour later, he was back on a moose carcass. At 5:45 p.m., he rested for about five hours. He started up again at 10:16, approached another bear at 10:31 -- possibly one of the sows he met earlier. He ate again at 11 and bedded down at 11:30 p.m. Dale said the department is evaluating further use of video collars and will consider using them on bears that have not been spotted at kill sites. "It does seem to be a pretty powerful tool," he said. Coller-cam: A day in a bear's life" From here. Boar Predation :   Musk Oxen Predation : More brown bears lean towards herbivory than towards carnivory, but both varieties exist, and have existed in ancient times. Even when brown bears coexisted with such hypercarnivores as the European cave lion and cave hyena. I suggest both are stable, but diet depends on what food sources are available. Especially fruits or salmon which may allow for higher population densities and focuses on consumption of these food sources. Of the populations in North America several were in the area of ~50% terrestrial meat in the diet (obviously less than the ~100% for big cats). Males would have averaged higher (and females lower), and then there is substantial individual variation (as shown by the graph from the same source-with one 10 year old male having a diet of about 95% terrestrial meat, for example). Some populations that weren't included, like the bears of GMU13, which may have high terrestrial meat averages (or at least, some highly predatory individuals) as well. Deep snow was associated with the ability of bears to kill (especially surplus kill) muskox, but a large difference between the kills of brown bears and wolverines is that those brown bears kill often appeared to be in good condition.   From Predation and multiple kills of muskoxen by grizzly bears. All O.P'ed by Ursus in the 'Grappling Dilemma' thread. Edited by Canidae, Dec 29 2012, 03:10 AM.
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| Ursus arctos | Dec 29 2012, 02:26 PM Post #32 |
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Autotrophic Organism
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Contributions are highly encouraged! Thanks for the post. BTW, the Russian info on boars came from Warsaw (the poster). To add regarding muskox: Finds for the Alaska Board of Game: Predation by brown bears was identified as a primary source of mortality on muskoxen and is an important cause of the failure to achieve the population and harvest objectives. During 2007-2011 , brown bear predation was identified as the primary source of mortality. Sixty- two percent of the documented total adult muskoxen mortality (n=73) was attributed to brown bear predation, which accounted for an average of 9 adult muskoxen deaths annually. During the same time period, 58 percent of documented calf mortality (n=45) was caused by brown bear predation. This resulted in an annual average of 5 calves known to be preyed on by brown bears. Apparently brown bears cause the majority of adult and calf muskox mortalities, in that study. Mesopredator, Just 1 comment: I agree region is "basically food availability". It is also worth noting though that food availability has influence on hibernation; further North they generally have to hibernate longer due to longer winter periods when food doesn't grow. Its interesting to consider the impacts latitude has on spring vs autumn weights. Some info form: Swenson, J., Adamic, M., Huber, D., Stokke, S., 2007. Brown bear body mass and growth in northern and southern Europe. Oeccologia 153, 37-47. Asymptotic body mass values: Southern male European brown bears in spring: 248 kg Male, autumn: 243 kg Female, spring: 115 kg Female, autumn: 141 kg North, male, spring: 201 kg Male, autumn: 273 kg Female, spring: 96 kg Female, autumn: 158 kg Of course, besides hibernation length diet ties into these differences as well. A quote: "Seasonal changes in body mass In spite of the overall lack of difference in body mass between populations, the analyses revealed some important patterns. Although body mass was greater in autumn than spring in the global linear models, bears in the north had a greater change in body mass between seasons. Based on the analysis of asymptotic body masses, northern females gained more mass (62 kg) than southern females (25 kg) from spring to autumn. Correspondingly, adult northern females lost more mass from autumn to spring compared to southern females. The greater seasonal changes in body mass in the north compared to the south are not surprising considering that northern bears hibernate longer than southern bears. Northern bears hibernate for 5.3– 6.5 months, depending on sex and reproductive category, in central Scandinavia and 6.9–7.5 months in northern Scandinavia (Manchi and Swenson 2005). In the south, however, the mean denning time is 2.9 months, and tracks and fresh scats are observed in all winter months, sug- gesting that many bears do not hibernate for the entire winter and that some may not hibernate at all (Huber and Roth 1997). Nondenning brown bears have also been re- ported from Italy (Roth et al. 1992) and Spain (Naves and Palomero 1993). Differing trends in body mass within the spring season Population differences were observed in body mass change during the spring season. Although the regressions with the best fit were often cubic, the trends were for increases for both sexes in the north and decreases in the south. Noyce and Garshelis (1998) challenged the existence in bears of the spring ‘‘negative foraging period’’ with declining body mass, but both increases and decreases in body mass have been reported for brown and North American black bears (U. americanus) in North America (Noyce and Garshelis 1998; Rode et al. 2001; Schwartz et al. 2003). The decline in mass during spring in the south occurs despite the unnatural situation of feeding of brown bears by humans in both countries. In Slovenia, the law requires one bear- feeding site per 6,000 ha in the brown bear core area (Simonic 1994), but bears also make intensive use of ungulate feeding sites stocked with corn (Große et al. 2003). Bears are not fed by humans in Sweden or Norway. An important difference between populations may be the availability of high-protein foods, because spring mass gain by brown bears is 64% lean body mass (Hilderbrand et al. 1999b). In the south, corn is available year-round (ca. 580 g/ha/year), but the availability of provided meat de- clines rapidly from late winter to summer (Große et al. 2003). In the north, ants are 100 times more available than in the south (Große et al. 2003), moose is an important food in spring (Dahle et al. 1998; Opseth 1998; Persson et al. 2001), and consumption of meat and insects in spring is far higher than in the south (Table 1). Although brown bears can gain mass in spring on a protein-rich forb diet (Rode et al 2001), protein digestion is higher for meat than plant diets (Pritchard and Robbins 1990). We suggest that the greater availability and use of protein-rich meat and insects in the north promotes greater mass gain in spring." Today, some info on the diet of Japanese brown bears. First source: Aoi, T., 1985. Seasonal Change in Food Habits of Ezo Brown Bear (Ursus arctos yesoensis Lydekker) in Northern Hokkaido. Research Bulletins of the College Experiment Forests Hokkaido University 42, 721-732. You can download the article here. The article used fecal analysis and stomach contents ( =( ). I am not sure about any methods of correction, as it says it followed the methods of Tisch 1961, a masters thesis that is not available on line. The importance values= % Frequency of Occurrence x % Volume/100 IMO, % volume is a better indicator of importance than the "importance values", but whatever. Here are samples by season:  Important for knowing how heavily each season is weighted for the overall data. Spring:  Summer:  Autumn:   Overall data:   Visual representations:  These bears are highly herbivorous. More info on Japanese brown bears can be found from: Sato, Y., Mano, T., Takatsuki, S., 2005. Stomach contents of brown bears Ursus arctos in Hokkaido, Japan. Wildlife Biology 11, 133-144. Stomach content info may be biased by differing rates of movement of different food types through the stomach, but I don't know of any info on this. Data is divided up into three regions, but it is clear these bears are highly herbivorous (same as the study above). Mammals make up only a small slice of these pie charts:  Sika deer feeding is discussed by the article:  And likely highly related to human-killing of deer. Bears with deer in their stomach contents also often had maggots as well, suggesting these deer were often scavenged. Deer carcasses In the early 1990s, bears in eastern Hokkaido con- sumed sika deer meat only during late summer and autumn (see Fig. 3). After 1994, however, deer meat appeared in the diet in spring and early summer. Year- round use of deer by Hokkaido brown bears is unique; bears in other areas eat ungulate meat mostly in spring (Boertje et al. 1988, Green et al. 1997, Mattson 1997), except in northern Europe (Danilov 1983, Persson et al. 2001). In northern Europe, ungulates are frequently attacked by bears and comprise the most important food for bears during summer (Persson et al. 2001), sug- gesting that brown bears are generally more carnivorous in northern areas (Danilov 1983, Persson et al. 2001). The range of Hokkaido brown bears, however, is locat- ed at the southern limit of Asian brown bears (Servheen 1990). We consider it probable that Hokkaido brown bears consume deer meat more by scavenging on carcasses than by aggressive predation, for the following rea- sons. About 30,000 deer were hunted between 1994 and 1999 (during November-January) and more than 20,000 deer were shot for nuisance control throughout the year, outside the hunting season (Hokkaido Government 2000). After shooting the deer, hunters in eastern Hok- kaido often leave the carcasses in the fields (HIES 2000, Lead Poisoned Eagles Network 1999, 2000, 2001); these would then be consumed by bears. The high incidence of maggots in the stomachs that contained deer meat suggests that bears scavenge on deer. Since deer- control measures are often applied near crop fields, and consequently deer carcasses are often left there, encounters between people and bears become more frequent in such areas. This problem is more serious in Hokkaido, where people live in close proximity to bear habitat. Anyway, tables by region:    If anyone has questions, would like me to try and focus on any area, etc, let me know. |
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| Mesopredator | Dec 29 2012, 10:53 PM Post #33 |
Disaster taxa
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Yes. Good point. Now I think about it, I do have a question. If a bear doesn't hibernate, does it still need carbohydrates? By the way, I knew bears eat insects, so ants do make sense, but I didn't know ants were 'important' (not the best choice of a word). I don't mind which area, I'm keeping track on this information anyway. But, I'm very interested in Syrian brown bears, Gobi bears and Tibetan blue bears. Though I can understand information about them is rather scarce, so really, I don't mind which area. If I haven't said so; thanks for sharing this. |
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| Ursus arctos | Dec 30 2012, 08:21 PM Post #34 |
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Autotrophic Organism
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I quoted an article on Tibetan blue bears (Ursus arctos pruinosus) before. You can download the full article here. For reference:
In summer Tibetan blue bears are highly carnivorous. The authors suggest that the wild yak is scavenged, but as they only collected feces some level of predation is still a possibility. Wild yak are very big however, and the (admittedly far less carnivorous) Yellowstone grizzly have not been known to prey on adult bison. Unfortunately I can't find published info on Syrian brown bears or Gobi bears. Regarding ants-yes, they can be important. Especially so for populations like the Flathead drainage bears which have otherwise very low protein diets. Those bears gain weight rapidly during the summer, but their lean body mass actually decreases at that time due to insufficient protein consumption. The info is from: McLellan, B.N., 2011. Implications of a high-energy and low-protein diet on the body composition, fitness, and competitive abilities of black (Ursus americanus) and grizzly (Ursus arctos) bears. Canadian Journal of Zoology 89, 546-558. Although insects were much more important for black bears than brown bears, it probably made an important contribution to protein intake. -I recall seeing at least one article published specifically on brown bear consumption of ants in the genus Formica in Europe. I am tired, as it is almost 5 am now, so I will provide more info on insect consumption later. |
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| Mesopredator | Dec 30 2012, 09:17 PM Post #35 |
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Disaster taxa
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Thanks. And take your time, no need to hurry.  Now, I have another question besides this one: -If a bear doesn't hibernate, does it still need carbohydrates? This one is a bit difficult to answer I think, so I'm not counting on a answer, but here it goes: -For a human it is healthy to have a diverse diet, does this apply to bears too? Of course even if it does, I don't think bears are trying to get a diverse diet - just what's available, has the most calories and is easy to catch. Edited by Mesopredator, Dec 30 2012, 09:29 PM.
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| Ursus arctos | Jan 4 2013, 10:05 AM Post #36 |
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Autotrophic Organism
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Info from: Große, C., Kaczensky, P., and Knauer, F., 2003. Ants: A food source south by Slovenian brown bears (Ursus arctos)? Canadian Journal of Zoology 81, 1996-2005. Discussion quotes: Ant availability The availability of ants in central Slovenia was only 1.4% of that in central Sweden. These result are not surprising, because the Eurasian taiga has been described as offering optimal habitats for forest ants that build large mounds (Savolainen et al. 1989). The high occurrence of clearings in Sweden, including a high content of dead wood and a low canopy cover, is advantageous for most ant species (Punttila et al. 1991). Similarly, we found the highest density of ants in Slovenia in former clearings and natural thickets. Brown bears are seeking these areas for cover during the day (Kaczensky 2000), and activity monitoring of brown bears in Slovenia often shows periods of high activity at the bed- ding site (P. Kaczensky, A. Wagner, F. Knauer, and M. Blazic, unpublished data). It appears that brown bears fre- quently make use of ants around daybeds, as every third ant colony was opened around these sites. Forty percent of the bedding sites from American black bears are also classified as “feeding–bedding sites”, as three quarters of bedding sites show that logs and rocks had been rolled over, presumably in search of insects (Mollohan 1987). In Slovenia, former clearings seem to be of double benefit for brown bears, as they provide both cover and food. A similar situation has been observed for the black woodpecker (Dryocopus martius) in Scandinavia (Rolstad et al. 1998). Preference for certain ant species Brown bears in Slovenia showed a prefererence for the large-bodied genera Camponotus and Formica and clearly avoided the Myrmicinae (Table 6). Camponotus spp. contain more fat, less formic acid, and is easier to digest owing to the lower dietary fibre content than other ants of the boreal forest (Swenson et al. 1999). The preference for Formica spp. in Slovenia was largely a result of their consumption in the spring, a time when mound-building Formica spp. con- centrate at the top of their mounds to bask in the sun, and thus brown bears are able to harvest substantial amounts without consuming much anthill material; a situation well documented in Sweden where red forest ants are abundant (Johansen 1997; Swenson et al. 1999). Nevertheless, the smaller ants of the genus Lasius consti- tuted the bulk of the ants consumed (Table 5). They may not be as large as Formica spp. and Camponotus spp., but they are the most abundant. In addition, their small body size, and thus the expected low efficiency of biomass intake per unit time, is most likely compensated for by the fact that only Lasius spp. occur frequently in large and extra large colonies (Table 4). In Minnesota, American black bears also most heavily preyed on Lasius spp., in particular the yellow ant Lasius umbratus. Their attractiveness to American black bears was explained by the dense concentrations they some- times form in the nest, their slow evacuation of the brood, and their passive defense-response traits. However, other Lasius spp. did not show these traits (Noyce et al. 1997). Be- cause we were not able to distinguish different Lasius spp. in the brown bear scats, we cannot provide evidence that the behavioural traits of certain ant species made them more at- tractive to brown bears than others. In general, feeding patterns of brown bears in Slovenia support the hypothesis that brown bears preferably exploit ant species that allow the most efficient foraging. However, we do not have any explanation why Myrmicinae, which are abundant and about the size of Lasius spp., are largely avoided. The avoidance of Myrmicinae seems to be a com- mon pattern. In a comparison of ant predation by mammals, Redford (1987) described Formicinae as being generally preferred and Myrmicinae as being the least preferred. He attributes this to the lack of a functional stinger in Formicinae, which is absent in Myrmicinae. For an animal like the brown bear that frequently exploits the nests of bees and wasps, this does not seem to be a very likely explana- tion. More detailed analysis of the defence behaviour, as well as the dietary and formic acid content, of the different ant species would be needed to more thoroughly discuss the observed prey choice by brown bears. In addition, seasonal differences in the feeding strategy of ants have been ob- served (Cannon and Fell 2002), which most likely have con- sequences on the nutrient levels of ants, and thus may affect prey choice by brown bears. Seasonal availability and use of food items Ants occurred in scats in high frequency and high FV for about 9 weeks in the summer, a pattern also observed else- where (Mattson et al. 1991; Noyce et al. 1997; Landers et al. 1979; Bull et al. 2001; Mattson 2001). In the summer, feed- ing on ants coincides with peak availability of pupae (Noyce et al. 1997; Swenson et al. 1999). However, Swenson et al. (1999) did not find a feeding preference for pupae or a sig- nificant difference in the dietary content of pupae versus workers of Formica spp. In their study, ant use by brown bears decreased in the summer when neonate moose (Alces alces) became available, whereas ant use decreased in mid- summer in Minnesota when fruit became available to Ameri- can black bears (Noyce et al. 1997). In other studies in Spain and in Yellowstone, ant use by bears was highest in years or seasons when other food items were scarce (Clevenger et al. 1992; Mattson et al. 1991; Mattson 2001; Bull et al. 2001). Furthermore, a regression model to predict the probability that ant nests in or under woody debris were consumed by grizzly bears in Yellowstone identified vegeta- tion structure, average monthly temperature, and annual abundance of high-quality foods as the best predictors of ant use by bears (Mattson 2001). It is therefore generally as- sumed that ants are just a secondary food item which is im- portant during a limited season or when other food sources fail. In the Slovenian summer, feeding on ants also roughly co- incided with the relatively low abundance of other high- caloric items such as meat, green vegetation (taking into ac- count the nutrient and fiber contents), and fruits (Table 4). However, the coincidence was not at all that strict as one high-energy food item, dry corn, was available year-round at the artificial feeding sites. In addition, even in the fall after fruit became abundant, ants were still regularly found in brown bear scats, although in reduced volume and fre- quency. Thus, ants seem to be more than a secondary food source for brown bears in Slovenia. Importance of ants The overall availability of ants in Slovenia was only 1.4% of that in Sweden, excluding Myrmicinae, which brown bears did not eat. The available biomass of ants was only 0.65% of that in Sweden. Despite this, brown bears in Slovenia still ate half as many ants as brown bears in Swe- den. In the summer, contribution of ants to total dietary in- take was nearly equal in Slovenia and Sweden, which amounts to a relative use of ants that is about 30 times higher in Slovenia than in Sweden. These results indicate that ants are an important food source for brown bears and we reject the hypothesis that ant consumption in Slovenia is proportional to the overall ant availability. Brown bears in Slovenia clearly do not feed on ants owing to a lack of alternative food sources, as high-caloric foods are readily available at hunters’ feeders throughout the year. Dry ant biomass averaged 135 g/ha or 26 kg live ants/km2, whereas carcasses and corn at feeding sites provided a mini- mum of 190 and 580 g/ha, respectively (Lovskih Organizacij Slovenije 1998). Additional carcasses of domestic animals and slaughter/hunting remains were regularly dumped in the forest and were not included in this estimate. Although corn was available in at least the same amount as ants, brown bears seemed to prefer ants to corn during the summer. Although it may seem inefficient for the brown bear to feed on such tiny animals as ants, finding an ant colony may be much less time consuming than finding a piece of carrion or killing an adult ungulate (i.e., the ratio of “time expended searching and feeding on the prey/gained energy” (Krebs and Davies 1993) is probably better for preying on ants than for preying on ungulates or searching for their carcasses). In addition, artificial feeding sites do not provide security cover and brown bears risk encounters with people and other brown bears. Presumably, the importance of ants to bears was even greater before hunters contributed so heavily to the bears’ food availability. Berries and beech nuts have never been a plentiful or reliable food source in Slovenian forests, in contrast to green vegetation and ants. The prediction by Swenson et al. (1999) that the importance of ants will in- crease on a north–south gradient clearly holds true in Slovenia; however, the factors leading to this high impor- tance of ants are not yet fully understood.  Here are ants in the Slovenian brown bear dietary info.  Formica especially was used far out of proportion of its availability. Also note how Swedish brown bears compare, where ants are around 100 times more abundant. Food source vs time:  ~~~ Anyway, I'd like to add that the Flathead brown and black bears (discussed in the article "McLellan, B.N., 2011. Implications of a high-energy and low-protein diet on the body composition, fitness, and competitive abilities of black (Ursus americanus) and grizzly (Ursus arctos) bears. Canadian Journal of Zoology 89, 546-558.") ate ants, which are considered a high protein food, in summer. Nonetheless, they still lost lean body mass during this time, due to the overall extremely low protein content of their summer diet. I imagine any protein they could get (to curb the loss of lean body mass) was valuable, likely making ants at least a moderately important food source for these bears. 7% dietary content for black bears and 3.5% for brown bears during summer. Of course, those fruits that dominated their summer diets and allowed them to rapidly gain weight (fat) were the most important. The Slovenian brown bears though looked like they have a diet far higher in protein than the flathead bears, so I don't believe this is the reason for high preference of ants. I just thought this was worth bringing up. ~~~ On a departing note, I wanted to add that the "red imported fire ant", a pest here, is a member of Myrmicinae-the subfamily of ants avoided by brown bears. Can't say I blame them, but the article by Große, et al, notes they attack bees and wasps, whose stings are at least as bad... |
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| Mesopredator | Jan 4 2013, 09:19 PM Post #37 |
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Disaster taxa
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Yes! More brain food! I was eagerly waiting for this.  As I understand, and you may always correct me if wrong, ants can be, somewhat, important in summer or spring. However it's a secondary food, as it may be eaten when food is scarce. I would think ants are a easy mail, so if I was a bear I would feast on it. But of course as fruit is more benificial (for gaining fat) and just as easier to get if not easier, I would eat that instead. I got a theory why bears attack bees and wasps and not the ants. It's a thought so it may be utterly wrong. Honey is delicious, high in energy I believe, so is worth the attack. Wasps and wasp larvae are probably tasty as well. However I think that the myrmicinae taste horribly, or bad. I would think the myrmicinae formic acid would be greater than in other species. (Taste gives you an idea if something is worth it or not. That's why we love candy and fast food, because it's high in calories, fat or sugar. But I'm guessing you know that.) Let you tell me what you think. |
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| Ursus arctos | Jan 8 2013, 02:28 PM Post #38 |
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Autotrophic Organism
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I agree. Chances are there is more fruit mass/land area.
Bees and wasps do not show up in percentages nearly as high as these ants in any population I know of. An explanation would have to explain why the appeal vs costs differ enough to produce drastic differences in diet content between myrmicinae and other ant types. Does formic acid content strongly impact taste? These are questions I don't know the answer to. ~~~~ Anyway, prehistoric brown bears! (& notes on competition with native species) Info from: Matheus, P., 1995. Diet and Co-ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia. Quarternary Research 44, 447-453. They analyzed extracted collagen of 16 short faced bears and 14 brown bears from central Alaska and west-central Yukon territory. 6 modern bears from Admirality Island and 7 from the Alaska Peninsula were also analyzed. Two of the A. simus specimens were dated. NMC 7438 is 26,040 +/- 230 years old. NMC 37577 is 29,600 +/- 1,200 years old. The article states the other fossils, particularly of Arctodus, are older based on the sediments having been assigned a "Rancholabrean age". Areas associated with diets:  Where those modern brown bears fall:  Many of those bears have diets that appear extremely heavy in marine foods. Which readers hopefully already know from the opening post (70%+ is common; up to 82% in Black Lake bears), but more evidence the merrier. And a point of reference for interpreting graphs such as the above. Extinct bear diets:  One of those brown bears looks like he must have heavily fed on salmon. For the rest, I disagree with the author's interpretation. But I'll provide the author's quotes first.     My problem is this- with the exception of one of the Alaskan brown bears, those bears grouping with A. simus have relatively lower 13C/vs PDB than the A. simus specimens. The bears in the same 15N range are overall a little shifted toward the left. Which to me seems inconsistent with the suggestion that these bears consumed moderately heavy marine diets mixed with herbivory. My expectation would be for a herbivory + salmon mix to look close to terrestrial would have net-featured a shift slightly to the right-rather than left, like in the brown bears relative to A. simus. --However, if the isotope values plotted are logs, then it would likely be wrong to assume straight line movements as values change; I don't know much about isotope analysis-- I don't think it looks like strong enough evidence to reject that idea either, however, because some of the modern marine bears were high on 15N but still fairly moderate on 13C. The author also argued A. simus was a lightly built scavenger, built for efficiently traveling great distances and compensating for a lack of formidability relative to size with lots of it (size) to intimidate predators off of kills. I don't think this view is well supported at all morphologically. A. simus was classified as semi-fossorial by the descriminant function analysis of "Postcranial morphology and the locomotor habits of living and extinct carnivorans"-far from the cursorial locomotor group. Definitely not closer than extant bears. This was probably the scientific article that really started that popular myth. ~~~ Info from: Bocherens, H., Drucker, D., Bonjean, D., Bridault, A., Conard, N., Cupillard, C., Germonpré, M., Höneisen, M., Münzel, S., Napierala, H., Patou-Mathis, M., Stephan, E., Uerpmann, H., Ziegler, R., 2011. Isotopic evidence for dietary ecology of cave lion (Panthera spelaea) in North-Western Europe: Prey choice, competition and implications for extinction. Quarternary International 245, 249-261. The article was about the cave lion, rather than bears, but it mapped much of the entire ancient communities. A major dividing line was the last glacial maximum (LGM), when a series of extinctions (including the cave bear and cave hyena) occurred. Pre-LGM map of two regions:   The lines drawn from the lions to a box indicate an average value range of what that lion ate. Knowing that, you can guess at which prey the lions were eating, and also make guesses about the diets of the other animals, like brown & cave bears, as well as hyenas. Cave bears were clearly very herbivorous, while many brown bears were mixed in with the other hyper-carnivores. A couple brown bears were mixed with the herbivores as well. A quote: In the Ardennes, cave lions exhibited the most widespread isotopic values of all analyzed carnivores. The range of d13C values was almost 2& and the range of d15N values more than 3& (Table 2). Hyenas exhibited a smaller range of d13C and d15N values although twice as many samples were analyzed, leading to a much smaller standard-deviation than for cave lions (Table 2). Some of this clus- tering of data may be due to the scavenging of prey killed by other predators by hyenas, but since cave hyenas were more active pred- ators than modern ones (Baryshnikov, 1999), this should reflect mainly a similar prey choice for the analyzed specimens. Most of the predator species exhibited individual d13C and d15N values that overlapped with the area covered by the isotopic values of hyenas, in particular leopard, wolverine, and the brown bears with the highest d15N values (Fig. 2). In contrast, lions and wolves seemed to scatter around the area occupied by hyenas and other carnivorous species, with either less negative or more negative d13C values or less positive d15N values (Fig. 2). Only one lion specimen fell in the area of the graph occupied by hyenas and brown bears. This specimen was directly radiocarbon dated and is one of the youngest specimens in Belgium, with an age of 24,470+/- 210 14C BP. As the youngest dated cave hyenas are 27,000 years old in Belgium (Germonpré, 1997), this would mean that this cave lion individual lived after the extirpation of cave hyenas and that cave lions could shift their diet to include prey that were previously mostly consumed by hyenas only after this predator was absent. This supports further the hypothesis of a competitive displacement of cave lions by cave hyenas. In combi- nation with evidence for fights between cave hyenas and cave lions and that cave hyenas sometimes consumed carcasses of lions during the Late Pleistocene (e.g., Diedrich, 2008, 2009a), this indicates that lions were at a disadvantage in the competition with hyenas. This could be linked to the solitary habits of cave lions in contrast with the clan behaviour of cave hyenas. This is in contrast with modern spotted hyenas and lions in Africa, where both predator species exhibit a large overlap in the prey choice (Hayward, 2006). Modern lions, even if they are smaller than the Pleistocene ones, may resist better the competition with spotted hyenas thanks to their collective behaviour. In contrast, carnivorous brown bears could sustain die- tary competition with hyenas using overlapping prey items as Pleistocene brown bears were even larger than modern ones (e.g., Baryshnikov and Boeskorov, 2004) and therefore much larger than hyenas, while leopard could use food caching to protect their prey from competing hyenas, as they do nowadays for instance when they are in competition with tigers (e.g., Seidensticker, 1976)." I'm not sure if failure of these lions to compete successfully with hyenas for kills is really the best explanation. Either way, the hyenas went extinct and the lions didn't following the LGM. Post LGM:   The second graph didn't include brown bears, but I decided to add it anyway. A quote: "Interestingly, post-LGM brown bears exhibit d15N values similar to those of herbivores and differ from pre-LGM brown bears that were more strongly carnivorous." My guess is that the massive cave bears could exclude brown bears from the most productive vegetation, and their extinction opened up a new niche opportunity for the local brown bears. Basically that, while abundant quality vegetation existed before, the presence of cave bears may have made the environment effectively like those poor in vegetation featuring highly predatory brown bears today-by simply denying access to the brown bears. The cave bear's unfortunate extinction thus allowed a shift to herbivory. |
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| Mesopredator | Jan 8 2013, 09:14 PM Post #39 |
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Disaster taxa
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Neither do I know if formic acid does imply a foul taste. Predator relationships, like the cave bear is interesting. Like said bears benefit from wolves, because of carcasses. But bears do not seem to benefit from coyotes as these may eat carrion before bears can find them. My conclusion about cave bear and brown bear relationship is the same like yours. Cave bears would indeed compete for food availability, which may indeed cause brown bears to eat less vegation. With cave bears gone, individual brown bears may also compete less with eachoter. Individual bears could become more herbivorous to avoid competition. Who knows, maybe someday brown bears may once again give rise to a herbivorous species like the cave bear. I'm wondering if black bears and asian black bears (but those don't overlap right?) cause brown bears to change their food or if it is only the other way around. Something else I recently thought of; what is the relationship between cave hyenas, cave lions and brown bears. I would think unlike with wolves, bears can't profit from carcasses. I would think brown bears wouldn't be able to compete with them and may go in area's which lions and hyenas don't like; I'm thinking of mountains and to a lesser extent, though important, forests. Edited by Mesopredator, Jan 10 2013, 04:38 AM.
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| Kurtz | Jan 16 2013, 03:53 AM Post #40 |
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Kleptoparasite
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GRIZZLY BEAR PREDATION ON A BULL BISON IN YELLOWSTONE NATIONAL PARK http://www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_13/Wyman_13.pdf |
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| Ursus arctos | Apr 11 2013, 11:25 AM Post #41 |
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Autotrophic Organism
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 Jacoby ME, Hildebrand GV, Servheen C, Schwartz CC, Arthur SM, Hanley TA, Robbins CT, Michener R. 1999. Trophic Relations of Brown and Black Bears in several Western North American Ecosystems. Journal of Wildlife Management 63: 921-929. Note the high meat consumption by male brown bears in many regions. While the article said these estimates were supported by observations in some regions (such as Yellowstone), possibility of error exists: The high dietary meat content estimated for historical brown bears in Colorado, New Mex- ico, and Arizona may be due to 1 or both of 2 reasons. First, these values must be viewed in the sociocultural context of the period (before 1930) when most bears were collected. This pe- riod was characterized by the lack of modern veterinary medicine (e.g., antibiotics, vaccines, mineral supplements) and droughts and floods that led to extensive livestock losses (Brown 1985). Although brown bears at this time were universally regarded as major livestock preda- tors and were killed by government hunters who donated skins or skulls to museums, these bears may equally have been consuming live- stock that died of natural causes. Stable isotopes cannot distinguish between carrion and live prey. A confounding factor that may have led to a shift toward livestock depredation was massive overgrazing, which depleted natural food re- sources (e.g., grasses, forbs, rodents) historically used by bears (Brown 1985, Abruzzi 1995). The second potential reason is a technical problem that complicates the use of stable iso- topes in some ecosystems when a major differ- ence occurs between the signatures of the av- erage plant foods consumed by bears and the herbivore used to generate the baseline. For ex- ample, oak (Quercus spp.) mast was an impor- tant fall food for brown bears in many south- western ecosystems (Brown 1985). The nitro- gen isotope signature of Gambel's oak (Q. gam- belii) acorns (2.5%o) in Colorado and New Mexico would produce a bear signature of 7.0%o (as compared to 4.3%o used as the her- bivore baseline) if consumed as the sole diet (Hilderbrand et al. 1996:Fig. 3), which would dramatically reduce our dietary meat estimates. For example, if one assumed that one-third of the annual nourishment consumed by black bears in the Southwest sample came from acorns, the dietary meat estimate of 39% drops to 20%. The high dietary meat estimate (90%) for the Colorado 'Weisman" brown bear killed in 1979, although there was no suggestion of either livestock depredation or garbage avail- ability in the area where this adult female was killed (Peterson 1995), further suggests the di- etary meat content for southwestern bears was overestimated. This example indicates the need for caution in applying this technique. |
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| Scalesofanubis | May 22 2013, 07:48 AM Post #42 |
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Omnivore
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Bears That Have No Fish to Eat Eat Baby Elk Instead Yellowstone National Park is a vast expanse of largely-untouched natural beauty, a tract of the Midwest home to bears and wolves and geysers and mountains. But where humankind’s direct influence is deliberately kept to a minimum, that strategy of do-no-harm doesn’t always seem to work. For the past few decades, lake trout have been taking over the rivers and lakes in Yellowstone, pushing out the local Yellowstone Cutthroat trout. The Greater Yellowstone Coalition: Yellowstone Lake and its tributaries once supported an estimated 3.5 million Yellowstone cutthroat trout. Since the illegal introduction of lake trout in the 1980s, the cutthroat population in Yellowstone Lake has plummeted. Catch rates for Yellowstone cutthroats have significantly dropped as more and more lake trout are caught every year. The precipitous drop in cutthroat numbers is a result of lake trout predating on cutthroat trout. But more than just affecting cutthroat trout, the invasion of the lake trout is being felt throughout the ecosystem. According to new research lead by Yale’s Arthur Middleton, the replacement of cutthroat trout with lake trout is leaving Yellowstone’s local population of grizzly bears without enough fish to eat. Middleton and colleagues: Historically, Yellowstone Lake harboured an abundant population of cutthroat trout, but lake trout prey heavily on cutthroat trout and have driven a decline of more than 90 per cent in their numbers. Although cutthroat trout migrate up shallow tributary streams to spawn, and are exploited by many terrestrial predators, lake trout spawn on the lake bottom and are inaccessible to those predators. Without fish, the grizzlies need something, and in their place the bears have turned to eating baby elk. In the late 1980s, grizzly and black bears killed an estimated 12 per cent of the elk calves in northern Yellowstone annually. By the mid-2000s, bears were estimated to kill 41 per cent of calves. The researchers say that by turning to elk calves in place of the now-gone trout, the elk population growth rate has shrunk by 2 to as much as 11 percent. The research reminds that the food web is in fact a web, and that the illegal introduction of a few trout can mean a whole lot of dead elk. http://blogs.smithsonianmag.com/smartnews/2013/05/bears-that-have-no-fish-to-eat-eat-baby-elk-instead/?utm_source=facebook.com&utm_medium=socialmedia&utm_campaign=20130521&utm_content=smartnewsbears |
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| UrsusHorribilis | May 23 2013, 01:40 AM Post #43 |
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Unicellular Organism
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Does anyone know where I can find any good sources on the typical predatory strategies and behaviours of the brown bear? The brown bear is one of the only three large carnivores on the planet that regularly preys upon large herbivores and I'm interested in learning about how it does it. Big cats like lions tend to prefer pouncing on their prey and going for a quick neck bite, but bears are built quite differently than lions and I would like to know how their hunting behaviour differs. |
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| Sicilianu | May 23 2013, 06:49 AM Post #44 |
Omnivore
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I am sure Ursus arctos would be able to help you. I am sure he will see your post at some point. |
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| Ursus arctos | May 23 2013, 09:38 AM Post #45 |
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Autotrophic Organism
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I wrote a bit about it here. Also, from here: Muskox Bull Killed by a Barren-Ground Grizzly Bear, Thelon Game Sanctuary, N. W. T. ANNE GUNN’ and FRANK L. MILLER2 INTRODUCTION Muskoxen and barren-ground grizzly bears are relatively common along the banks of the Thelon River in the Thelon Game Sanctuary. In June 1981 we were flying a helicopter search of the Thelon River area during a study of water crossings used by barren-ground caribou (Rangifer tarandus groenlandicus). In the early afternoon of 23 June we were flying eastward when we spotted a grizzly bear standing on its hind legs among willow (Sulix spp.) bushes in a clearing surrounded by black spruce (Picea mariana) on the north shore. As there were two gulls (Larus spp.) in attendance, indicating the possibility of a kill, we circled closer and could then see a dead muskox on the ground near the bear. The grizzly bear alternately reared up and dropped onto all fours as we came close and when the helicopter was about 100-150 m away, the bear galloped away. We landed near the carcass of an adult muskox bull lying on its left side. The carcass was intact except for some exposed flesh and head wounds. The nose was torn away and the nasal turbinal bones were crushed and the cartilage torn. The right ear was split and torn away at the base where there was a penetrating wound into the skull. Traumatized areas were hemorrhagic, indicating that the wounds were inflicted on a living animal. The hide and musculature had been removed in the lumbar and thoracic areas, exposing the vertebrae and the right scapula. The internal organs were still intact and warm to touch. Subsequent histological examination of the dental annuli of a first incisor indicated that the muskox bull was 9-10 years old. The greening sedges (Carex spp.) immediately around the carcass were trampled and we backtracked along a disturbed path to a heavily trampled area of 5 m in diameter about 15 m away. The willow bushes peripheral to that trampled area were flecked with blood clots and clumps of blood-stained muskox wool. The ground cover was beaten down and the ground surface disturbed in many places with footprints pushed 10-15 cm or more into wet soil. We suggest that the grizzly bear surprised the muskox bull while it was grazing on sedge (indicated by rumen contents). The bear most likely grabbed the bull above the muzzle. In response, the bull must have braced its front legs and tried to dislodge the bear, suggested by front-foot hoof prints driven deep (15 cm) into the churned-up ground. Either the bull collapsed or the bear swung him off balance. At that point, the bear probably transferred its bite to just below the back of the bull’s horn boss. After making the kill, the bear dragged the carcass to where we found it, and had begun feeding when we interrupted. We returned about 48 hours later and found a light grey wolf (Canis lupus) and a grizzly bear whose colouring suggested it was not the bear that had made the kill. The carcass was dismembered and had settled into the wet ground. Most of the muscle masses and the internal organs had been consumed and the limb bones were scattered around the hide. The rumen had been pulled from the carcass but had not been fed on. The destruction of the facial area was also the mode of attack of a barren-ground grizzly bear killing a caribou cow whose carcass we found on the Beverly caribou herd’s calving ground, northeast of the Thelon Game Sanctuary, in June 1981. Griffel and Basile (1981) described puncture wounds in the frontal or jugal bones of 109 of 332 bear- killed sheep (Ovis aires) in Idaho. The facial area is richly innervated, and Mystervd (1975) in Griffel and Basile (1981) suggested that unconsciousness and hypoxic asphyxiation would follow severe and sudden injury to that area. Also, the seizing of the muskox bull’s muzzle would reduce chances of the muskox using its horns to gore the bear and increase the bear’s chances of throwing the muskox offits feet. Solitary muskox bulls usually seem particularly alert, and their speed of response, size, strength, thick coat and horns must combine to make them a formidable quarry even for a grizzly bear. The location of this kill, at the edge of a small clearing where ambush by rushing from nearby cover was possible, suggests that the kill was opportunistic. The muskox bull was probably so intent on foraging on the new growth of sedges 10-20 cm high that he was not aware of his attacker until it was too late. The femoral marrow fat was pinkish-white and firm, suggesting good nutritional status, and we did not observe any obvious infirmities that would have made the bull particularly vulnerable. Tener (1965) summarized predation on muskoxen and noted that Pederson’s report of a possible kill by a polar bear (Ursus rnaririrnus) may be the only reported instance of bear predation. He further commented that predation by barren-ground grizzly bears is rare, since up to 1965 only Hornby (1934, in Tener, 1965) had observed bears feeding on muskoxen on the banks of the Thelon River. In the late 1970s A.M. Hall (pers. comm.) observed grizzly bears feeding on muskox carcasses along the banks of the Thelon River (see photograph of grizzly bear sleeping near partially- eaten bull muskox in Hall, 1980). In 1978, on the banks of the Thelon, Hall observed three muskox carcasses on which grizzlies had fed, but he could not determine whether the bears had killed or were scavenging the muskoxen. Hall (pers. comm.) believes that grizzly bear predation on muskoxen is high, especially on solitary bulls along the Thelon River, probably because the dense willow stands favour surprise ambushes. In June and July 1981, we saw only solitary bull muskoxen feeding in the willow stands, which leads us to the same supposition. Within 40 km of the carcass described in this paper, during the same flight, we observed five other grizzlies on the north shore. Pegau (1973) briefly described an apparent kill of a 2- or 3-year- old muskox by a bear but the carcass was almost com- pletely consumed, so scavenging could not be ruled out. The carcass was found on the Seward Peninsula, Alaska, where Grauvogel (1979) speculated that the slow rate of increase of the transplanted muskox herd might be partially attributed to grizzly bear predation on muskox calves, though no evidence was cited. Our account of an apparently healthy, prime adult muskox bull that was killed by a grizzly bear is the first documentation of such an event. I may edit this to add more accounts later. Please let me know if you want something specific. |
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