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Post by brobear on Mar 22, 2017 11:18:26 GMT -5
billingsgazette.com/news/state-and-regional/wyoming/study-yellowstone-trout-decline-pushes-bears-to-elk-calf-diet/article_092dad45-a63c-5aec-83ab-e255b5ca1050.html
Fewer cutthroat trout in Yellowstone Lake could be part of the reason that elk herds migrating out of the park are declining.
Two recently published studies conducted in Yellowstone National Park point to the connectivity between the decline of spawning cutthroat trout from Yellowstone Lake and a resulting shift in grizzly bear diets to elk calves.
“We were surprised to see this connection,” said Arthur Middleton, lead author of a study published in the Proceedings of the Royal Society B, in a telephone interview. The study was released Tuesday. Middleton wrote the article based on his doctoral dissertation at the University of Wyoming. He is now on a two-year postdoctoral fellowship at Yale University.
The shift in diet has reduced elk calf recruitment by 4 to 16 percent, Middleton postulated, and has hindered the population growth of migratory elk herds that use the Yellowstone Lake area by 2 to 11 percent. “It might be worth adding that we don’t think this is the answer to where the elk calves went, but it’s something we should think about with changes in bear diets and the change in elk calf numbers,” he said.
Other perspective
The studies' conclusions are no surprise to David Mattson, a U.S. Geological Survey wildlife biologist who spent 14 years studying grizzly bear foraging and diets in the Greater Yellowstone Ecosystem.
"I think it highlights what should be the obvious for any observer of Yellowstone, that it's a complex system," he said. "And grizzly bears are kind of the consummate connector of all of the species in that system."
Mattson said during his years studying bears in the mid-1980s and mid-1990s, it was a time of an enriched ecosystem with large herds of elk, bison and plentiful cutthroat trout.
"All of that's reversed," he said. "We're watching probably the first state of impoverishment in the ecosystem as far as grizzly bears are concerned."
Other study
Middleton was helped in linking the aquatic and terrestrial food webs by a study authored by Jennifer Fortin of Washington State University that detailed the diets of 27 GPS-collared bears in Yellowstone. Fortin’s study was published in February in the Journal of Wildlife Management. She worked with fellow WSU student Charles Robbins tracking the bears and analyzing their scat.
Her study showed a 70 to 95 percent decline in trout consumed by grizzly and black bears between 1997 and 2009. The study also found that grizzly bears killed an elk calf every two to four days in June while black bears killed an elk calf every four to eight days.
“They’re the ones who did the really detailed studies following grizzly bears around and studying what they ate to drill into bear diets,” Middleton said. “Without their work we wouldn’t have arrived where we did.” By the numbers
Pause Current Time 0:00 / Duration Time 0:00 Loaded: 0%Progress: 0%0:00 Fullscreen 00:00 Mute Possibly only in Yellowstone could such a connection be established by data. That’s because there’s a rich source of current and past studies on everything from the Yellowstone cutthroat trout’s precipitous decline by 90 percent since predacious lake trout were illegally introduced, to cow elk pregnancy rates and cow-to-calf ratios for migratory elk herds in the park.
“I was really synthesizing these studies,” Middleton said. “An important part of what I did with the co-author (Thomas Morrison) was to pull together studies on bear diets and elk populations and as we did we saw evidence for links.”
Looking at the numbers gives credence to what seems only logical: once cutthroat trout numbers declined, bears that were eating those fish had to supplement their diet with some other food source. Elk calves just happened to be available.
To understand the effect of the trout decline on fish-eating bears, consider this: Clear Creek, one of 124 tributaries to Yellowstone Lake used for spawning, saw a migration of more than 54,000 cutthroat trout in 1988. By 2007, that number had plummeted to just over 500 fish. Although nonnative lake trout have been blamed for most of the decline, cutthroat also suffered through drought, which dewatered some of the spawning streams, and infection by whirling disease.
Like cutthroat trout, Yellowstone’s northern range elk herd has also seen a significant population decline. In 1988, the elk population hit 19,000. This winter the herd was estimated at just over 3,900 animals. The elk have also suffered from drought, increasing infection from the disease brucellosis, hunting pressure, the reintroduction of wolves that mainly eat elk and an increase in the number of other predators, including bears and cougars. Although 80 percent of the northern range’s cow elk are getting pregnant, according to aerial surveys conducted in July and August near Yellowstone Lake, only 10 percent of the cows still had calves.
Synthesizing
One study cited by Middleton estimated that 68 grizzly bears – roughly 14 to 21 percent of the Greater Yellowstone Ecosystem’s population – relied on cutthroat trout as part of their spring diet. The fish spawn between mid-May and early August.
It was estimated that grizzly bears that dined on cutthroat trout ate more than 7,800 fish during the spawning season – more than 12,400 pounds. With the fish’s decline, that amount dropped to about 300 fish a year, or about 690 pounds. With elk calves weighing an estimated 39 pounds, grizzly bears would have to eat almost 300 elk calves to supplement the loss of those 7,500 cutthroat trout, Middleton estimated.
Another study estimated the elk calf predation by bears rose from 12 percent in the late 1980s to 41 percent by the mid-2000s.
Middleton’s paper notes that because grizzly bears are only one of 28 species that are believed to have depended on spawning cutthroat trout, “the broader ecological consequences of lake trout invasion are potentially tremendous.” “It’s worthwhile to emphasize the uncertainty of what the size of the effect might be,” Middleton said.
Worth noting
The paper argues that the findings are relevant to wolf management plans for the states that surround Yellowstone National Park – Montana, Wyoming and Idaho. The migratory nature of elk from Yellowstone into the surrounding states may indicate that “elk calf recruitment may not be as sensitive to wolf removal on some outlying winter ranges as to the number of grizzly bears and the availability of alternative grizzly bear foods on elk summer ranges in and around YNP.”
Middleton said his study is a “surprising connection and one that goes back to some fisherman’s decision that it was important” to illegally introduce lake trout into Yellowstone Lake. If lake trout can be suppressed through the park’s efforts to net adults and kill the eggs they have laid – an effort that began in 1998 -- perhaps the cutthroat trout can rebound and once again benefit the other animals of the ecosystem, including elk, Middleton said.
The other lesson, he noted, is that “perhaps we shouldn’t be so quick to compartmentalize fish and wildlife management. They may seem separate, but they are more closely linked than we thought. Yellowstone National Park has long known that, but it’s been slow to enter the popular realm.”
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Post by brobear on Mar 22, 2017 11:18:48 GMT -5
The Grizzly, Our Greatest Wild Animal by Enos Abijah Mills. In Alaska I saw a grizzly out at sea, swimming vigorously along between two islands that were seven miles apart. The grizzly is fond of water, is an excellent and enduring swimmer, and in the water fights effectively.
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Post by brobear on Mar 22, 2017 11:19:08 GMT -5
The Grizzly, Our Greatest Wild Animal by Enos Abijah Mills. The grizzly spends about a third of each year in hibernation. He may use the same den year after year, repairing and reshaping it; or perhaps he will dig a new one. Sometimes he goes outside his own territory for a den to his liking. He is sometimes driven forth during hibernation by landslides as well as by snow-slides and floods.
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Post by brobear on Mar 22, 2017 11:19:28 GMT -5
The Grizzly, Our Greatest Wild Animal by Enos Abijah Mills.
Perhaps it would be well if we could think of the grizzly as being largely vegetarian. He digs up roots; feeds on weeds, tender shoots of shrubbery, fungi, mushrooms, berries, seeds, rose-hips, pine-nuts, and acorns; and also eats bark like a rabbit and grass like a grass-eater. A bear will reach up and pull down the top of a plum tree, and, biting it off, eat the small limbs, the bark, the leaves, and the fruit. A grizzly browsing in a wild raspberry-patch will bite off the tops of the vines together with the berries, the leaves, and the thorns. Sometimes the twigs and terminal buds of the pine, the fir, and the spruce are eaten. One day I saw a grizzly approaching in a manner which indicated that he knew exactly where he was going. On arriving at an alder clump by the brook he at once began tearing off the bark and eating it. On another occasion I watched a bear strip nearly all the bark within reach from a young balsam fir. I have often seen places where bears had bitten and torn chunks of bark from aspens and cottonwoods. Though they also tear the bark from pine and spruce trees, I do not believe that this is eaten as frequently as the bark of the broad-leaved trees. During the first few weeks after coming out of the winter den much of the grizzly's food is likely to be of the salad order - juicy young plant stalks, watery shoots, tender bark, young grasses, buds, and leaves. In late autumn, just before hibernation, his last courses are mostly roots and nuts.
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Post by brobear on Mar 22, 2017 11:19:54 GMT -5
The Grizzly, Our Greatest Wild Animal by Enos Abijah Mills.
However, the normal grizzly is an omnivorous feeder. He will eat anything that is edible - meat ( fresh, stale, or carrion ), wasps, yellow-jackets, grasshoppers, ants and their eggs, bugs, and grubs. Of course he eats honey and the bees. He also captures snakes, and many a rat and rabbit. He is a destroyer of many pests that afflict man, and in the realm of economic biology he should be rated high. I doubt if a dozen cats, hawks, or owls annually catch as many mice as the average grizzly. The food of a grizzly is largely determined by locality. Along the streams of the northern Pacific Coast he lives chiefly upon fish, while the grizzlies in the Bitter Root Mountains and British Columbia generally feed upon roots and plants. Those in the Rocky Mountains of Colorado and the Southwest have a mixed diet.
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Post by brobear on Mar 22, 2017 11:20:18 GMT -5
The Grizzly, Our Greatest Wild Animal by Enos Abijah Mills.
The spring-beauty, the dog-tooth violet, and the shooting-star, both tops and roots, supply the grizzlies of some localities with much of their food, while in other regions they rarely, and possibly never, touch them, though they grow abundantly. The bears in the Bitter Root Mountains eat the shooting-star freely, while the violet and the spring-beauty are favored by the bears of the Selkirks. Yet, strange though it is, the bears of both localities pay little attention to carcasses which they find. One of the plant roots which the bears of British Columbia dig out in autumn until the ground is frozen, is a wild pea, the hedysarum. I frequently follow a grizzly whose home territory was close to my cabin in the Rocky Mountains. Apparently he liked everything. One day he spent hours digging out mice. On another he caught a rabbit. He ate a bumblebee's nest, and, with the nest, the grass, the bees, their young, their honey, and their stings.
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Post by brobear on Mar 22, 2017 11:20:40 GMT -5
The Grizzly, Our Greatest Wild Animal by Enos Abijah Mills. The grizzly eagerly earns his own living; he is not a loafer. Much work is done in digging out a cony, a woodchuck, or some other small animal from a rock-slide. In two hours' time I have known him to move a mass of earth that must have weighed tons, leaving an excavation large enough for a private cellar. I have come upon numbers of holes from which a grizzly had removed literally tons of stone. In places these holes were five or six feet deep. Around the edges the stones were piled as though for a barricade. In some of them several soldiers could have found room and excellent shelter for ordinary defense. When a large stone is encountered in his digging the grizzly grabs it in both fore paws, shakes and tears it loose from the earth, and hurls it aside. I have seen him toss huge stones over his shoulder and throw larger ones forward with one paw. Grizzlies show both skill and thought in nearly everything they do. They have strength, alert wits, and clever paws, and commonly work at high speed. Yet they appear deliberate in their actions and work in a painstaking manner.
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Post by brobear on Mar 22, 2017 11:21:42 GMT -5
www.livescience.com/53483-omnivores.html By Alina Bradford, Live Science Contributor | January 25, 2016 11:53pm ET Omnivores are the most flexible eaters of the animal kingdom. They eat both plants and meat, and many times what they eat depends on what is available to them. When meat is scarce, many animals will fill their diets with vegetation and vice versa, according to National Geographic. Size Animal omnivores (including humans) come in many different sizes. The largest terrestrial omnivore is the endangered Kodiak bear. It can grow up to 10 feet tall (3.04 meters) and weigh up to 1,500 lbs. (680 kilograms), according to the Alaska Department of Fish and Game. Kodiaks eat grass, plants, fish, berries and the occasional mammal. Ants may be the smallest omnivores. One of the smallest ants is the pharaoh ant, which grows to only 0.04 to 0.08 inches (1 to 2 millimeters), according to the University of Michigan. They eat a variety of foods that include eggs, carrion, insects, body fluids, nuts, seeds, grains, fruit nectar, sap and fungus. Omnivores in the food chain Like herbivores and carnivores, omnivores are a very important part of the food chain or web. “Some nodes in that web may have dozens of strands attached to it and if you remove that node the web can begin to fall apart,” Kyle McCarthy, an assistant professor of wildlife ecology in the University of Delaware’s College of Agriculture and Natural Resources, told Live Science. Creatures in the food chain or web are also classified into a system called the trophic system. The trophic system has three levels. The top level includes omnivores and carnivores. The second level includes herbivores (animals that eat vegetation) and the bottom level includes living things that produce their own energy, like plants. When one level of the trophic system is removed, all of the trophic levels below them are affected. This is called a "trophic cascade," explained McCarthy. Omnivores help keep in check both animal populations and vegetation growth. Removing an omnivore species can lead to vegetation overgrowth and an overabundance of any creatures that was part of its diet. Digestion Omnivores have very distinctive teeth that help with the digestion of their varied diets. They often have long, sharp, pointed teeth to rip and cut meat and flat molars to crush plant material. One good example is the human mouth. Humans have canines and incisors that bite and tear into food and molars and premolars that are used to crush food. While most animals have sharper, more pointed teeth for tearing and ripping, the concept is the same. Some omnivores, such as chickens, have no teeth and swallow their food whole, according to the Animal Nutrition Handbook. The food is softened in the stomach by hydrochloric acid and digestive enzymes. Then, the food gets broken down in the gizzard, a strong digestive muscle, and rocks that the chicken has swallowed. Omnivores have a different digestive system that either carnivores or herbivores. Carnivores have a very simple digestive tract because meat is easy to digest. Herbivores, on the other hand, can have very complex digestive systems that can include multiple stomach chambers and regurgitating food for rechewing, because plant materials are much harder to digest. Omnivores, for the most part, are somewhere in the middle. They have a limited ability to digest certain plant materials. Instead of trying to process the harder materials, though, the omnivore’s digestive tract sends the material out as waste. Why did some animals evolve to eat meat or vegetation while others eat both? It comes down to availability of resources. “In terms of evolving to be a meat eater or plant eater, basically, any place there is available energy you will have a ‘niche’ for a species to fill in the ecosystem,” said McCarthy. Meat eaters evolved in areas where meat was plentiful while herbivores evolved in areas where vegetation was plentiful. Omnivores are the most adaptive of all the species and thrive in a larger range of environments.
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Post by brobear on Mar 22, 2017 11:22:33 GMT -5
shaggygod.proboards.com/Food Habits of Grizzly Bears and Black Bears in the Yellowstone EcoystemBear Food Graph (25 KB pdf) www.nps.gov/yell/naturescience/upload/ynpfoodgraph-2008.pdfBears are omnivores that have relatively unspecialized digestive systems similar to those of carnivores. The primary difference is that bears have an elongated digestive tract, an adaptation that allows bears more efficient digestion of vegetation than other carnivores (Herrero 1985). Unlike ruminants, bears do not have a cecum and can only poorly digest the structural components of plants (Mealey 1975). To compensate for inefficient digestion of cellulose, bears maximize the quality of vegetal food items ingested, typically foraging for plants in phenological stages of highest nutrient availability and digestibility (Herrero 1985). The food habits of grizzly bears in Greater Yellowstone Ecosystem (GYE) have been described in detail by Knight et al. (1984) and Mattson et al. (1991). Overall, army cutworm moths, whitebark pine nuts, ungulates, and cutthroat trout are the highest quality food items available to grizzly bears in the GYE. These foods impart the greatest nutritive value in exchange for the least foraging effort (Craighead et al. 1995). Grizzly bear food habits are influenced by annual and seasonal variation in available foods. Spring From March through May, ungulates, mostly elk and bison, comprise a substantial portion of a grizzly bear's diet. Grizzly bears feed on ungulates primarily as winter-killed and wolf-killed carrion but also through predation on elk calves (Gunther and Renkin 1990, Mattson 1997). Some large male grizzly bears also prey on adult bison during early spring. Grizzly bears also dig up pocket gopher caches in localized areas where they are abundant. Other items consumed during spring include succulent grasses and sedges during early green-up, dandelion, clover, spring-beauty, horsetail, and ants. During spring, grizzly bears will also feed on whitebark pine seeds stored in red squirrel caches during years when there is an abundance of over-wintered seeds left over from the previous fall (Mattson and Jonkel 1990). Summer From June through August, grizzly bears continue to consume succulent grasses and sedges, dandelion, clover, spring-beauty, horsetail, and ants. In addition, thistle, biscuit root, fireweed, fern-leaved lovage, and army cutworm moths are eaten. Predation on elk calves continues through mid-July when most grizzly bears are no longer able to catch calves (Gunther and Renkin 1990). In areas surrounding Yellowstone Lake, bears feed on spawning cutthroat trout (Reinhart 1990). Starting around midsummer, grizzly bears begin feeding on strawberry, globe huckleberry, grouse whortleberry, and buffaloberry. By late summer, false truffles, bistort, and yampa are included in the diet, and grasses, sedges, and dandelion become less prominent. Throughout the summer, grizzly bears scavenge the remains of wolf-killed ungulate carcasses usurped from wolf packs. In late summer during the breeding season, grizzly bears scavenge the carcasses of bull bison that have been gored and die while competing for female bison. Fall From September through October, whitebark pine nuts are the most important bear food during years when seeds are abundant (Mattson and Jonkel 1990). However, whitebark pine is a masting species that does not produce abundant seed crops every year. Other items consumed during fall include: pond weed root, sweet cicely root, bistort root, yampa root, strawberry, globe huckleberry, grouse whortleberry, buffaloberry, clover, horsetail, dandelion, ants, false truffles, and army cutworm moths. Some grizzly bears prey on adult bull elk during the fall elk rut. Black Bears The food habits of black bears in the Yellowstone ecosystem are similar to those of grizzly bears. The primary difference is that meat and roots are less prominent in the diet of black bears (Knight et al. 1988). Black bears have short, curved claws better suited for climbing than digging. In contrast, grizzly bears have longer, straighter claws and a larger shoulder muscle mass which makes them more efficient at digging for food items in the soil such as roots, bulbs, corms, and tubers, as well as rodents and their caches (Herrero 1978). Overall, grizzly bears consume more meat and black bears more plant material. LITERATURE CITED Craighead, J.J., J.S. Sumner, and J.A. Mitchell. 1995. The grizzly bears of Yellowstone, their ecology in the Yellowstone Ecosystem, 1959-1992. Island Press, Covelo, California, USA. Gunther, K.A., and R.A. Renkin. 1990. Grizzly bear predation on elk calves and other fauna of Yellowstone National Park. Int. Conf. Bear Res. And Manage. 8:329-334. Herrero, S. 1978. A comparison of some features of the evolution, ecology and behavior of black and grizzly/brown bears. Carnivore 1(1):7-17. _____. 1985. Bear Attacks-Their Causes and Avoidance. Winchester Press, New Century Publishers, Inc., Piscataway, N.J. 287pp. Knight, R.R., D.J. Mattson, and B.M. Blanchard. 1984. Movements and habitat use of the Yellowstone grizzly bear. U.S. Dep. Inter., Natl. Park Serv., Interagency Grizzly Bear Study Team. Unpubl. Rep. 177pp. _____, B.M. Blanchard, and D.J. Mattson. 1988. Yellowstone Grizzly bear investigations: Annual report of the Interagency Grizzly Bear Study Team, 1987. U.S. Dep. Inter., Natl. Park Serv. 80pp. Mattson, D.J., and C. Jonkel. 1990. Stone pines and bears. Pages 223-236 in Proceedings-Symposium on Whitebark Pine Ecosystems: Ecology and Management of a High-Mountain Resource, U.S. Dep. Agric., U.S. For. Serv. 386pp. Mattson, D.J., B.M. Blanchard, and R.R. Knight. 1991. Food habits of Yellowstone grizzly bears, 1977-87. Can. J. Zool. 69:1619-1629. Mattson, D.J., B.M. Blanchard, and R.R. Knight. 1992. Yellowstone grizzly bear mortality, human habituation, and whitebark pine seed crops. J. Wildl. Manage. 56:432-442. Mattson, D.J. 1997. Use of Ungulates by Yellowstone grizzly bears Ursus arctos. Biol. Conserv. 81:161-177. Mealay, S.P. 1975. The natural food habits of free-ranging grizzly bears in Yellowstone National Park, 1973-1974. M.S. Thesis, Montana State Univ., Bozeman. 158pp. Reinhart, D.P. 1990. Grizzly bear habitat use on cutthroat trout spawning streams in tributaries of Yellowstone Lake. M.S. Thesis, Montana State Univ., Bozeman. 128pp. www.nps.gov/yell/naturescience/bearfoods.htm
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Post by brobear on Mar 22, 2017 11:23:12 GMT -5
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Post by brobear on Mar 22, 2017 11:25:41 GMT -5
First posted by Parvez - Interesting article, George Stevenson's brain appeared to be sweating, glistening on a bright red plastic picnic plate there in the heat of the day. It was big as a big man's fist, and all around it, on other picnic plates, were slivers of other brains, like so many thin-sliced neural hors d'oeuvres. Some looked like spreading river deltas, carved deep with winding channels. One looked just like an elk hoof, stuffed tight with morel mushrooms. With them on the table was a bone-white grizzly bear skull, top lopped to show inside, where Stevenson's juicy brown brain used to be. And beside that was a fully furred grizzly head, guillotined with eyes closed, ears perked up, sharp teeth curving over soft black lips.
These are the grisly tools Dr. Stevenson needs for his presentation: "Grizzly Bear Brain, Central Nervous System Structures." "These bears are amazing creatures," Stevenson said. "I believe they have the most impressive olfactory system of any animal on the planet. Their nose is the very best." Generally speaking, national park management, while admittedly complicated, is not brain surgery. Except today, when Stevenson, a pioneering neurosurgeon, has packed the room with Glacier National Park staffers for a brown-bag lunch seminar. Not a few of those brown bags were tucked quickly under chairs as Stevenson pried open the bear head and reached elbow-deep inside to point out its finer details. Mostly, he was pointing out the snout, a full nine inches of highly evolved scent detection. It is, he said, like no other nose in the world. A run-of-the-mill dog's sense of smell is roughly 100 times greater than a human's. A good hound dog's nose is perhaps 300 times better. But a bear's scent system, Stevenson said, is at least seven times better than the hounds. "It's remarkable," he said. "It's how they know the world." When humans think about their hometowns, they think in terms of visual maps - down this street to that avenue, turn left at the bank, right at the stoplight. But bears don't see things that way. To get to their favorite huckleberry patch, they don't follow the trail to the tree with the broken limb, and then turn left at the big mossy rock. "No, they have an olfactory map." Take the scent of the trail to the smell of the anthill, then follow the smell of water to the perfume of huckleberries. It is difficult, Stevenson said, for humans to imagine such a way of knowing, but for bears it's essential. Each spring, when they emerge from the den, they are literally starving. There's no time to wander around and look for food, to look for tracks in the snow and to follow them, perhaps, to a protein meal. "They have to smell food over huge distances, and then go straight to it," Stevenson said. "If they can't, they die." An odd hobby. Stevenson was a neurosurgeon from 1965 until 1993, a pioneer of micro-neuro surgery. These days, he lives near Yellowstone National Park and is affiliated with the University of Wyoming. Of late, he's been combining his lifelong career with his new neighbors the bears, and hopes to create a first-ever neuron-anatomy atlas of bear physiology, using brain anatomy to show how the big bruins work. The biggest trouble, he said, is finding bear bodies to study. Part of his presentation includes a clip from a National Geographic documentary, in which he and his colleagues are seen sedating a bear and sliding her gently into the cavernous den of a modern MRI machine. "You have to be very careful," he said, which seems a bit self-evident when you're talking about a bear in a hospital roo The job is somewhat less nerve-wracking if the bear is dead. Occasionally, Stevenson said, wildlife officials will give him a call when a bear is killed. Then he rushes to Bozeman, where the state of Montana's wildlife laboratory is located - and the bear's head is drained of blood, pumped full of formaldehyde, stabilized and prepped for transport. Then Stevenson puts it in his plastic cooler, hits the local grocery store for a bag or two of ice and heads for Missoula, where technicians at Community Medical Center work after-hours to make MRI images of bear brains. It is, he admits, a decidedly odd hobby. But it is paying off in terms of understanding how grizzly bears think and operate. Stevenson now knows, for instance, that the percentage of a bear's brain devoted to scent is at least five times greater than the percentage of human brain allocated to olfactory systems. In other words, humans smell in black and white, while bears enjoy the full kaleidoscope. "A polar bear will walk 100 miles in a straight line to reach a female ready to breed," he said. "That's what the bear's nose can do. They smell a million times better than we do." A human brain weighs in at about 1,500 grams, huge compared to a 450-gram bear brain. And yet our olfactory bulb is the size of a pencil eraser. The bear's is the size of your thumb. That's a lot of smell power for such a small brain. And even before the brain, he said, the bear's body is built to sniff.
The black pad on the bear's snout, like a dog's nose, is wired with hundreds upon hundreds of tiny muscles. Bears can manipulate their nostrils the way dexterous people control their nimble fingers.
The smells then travel up two 9-inch channels, with hundreds of times the surface area of a human's nose, to a spot where 10 million nerve strands and a billion receptor cells fire electrical signals directly into the brain, through countless tiny pathways and onto the brain's cribiform plate.
The large hippocampus "remembers" the scent, adding it to the mental map.
Just imagine the blinding brain punch a blast of pepper spray must deliver to that system.
"It's not just heat and discomfort," Stevenson said. "It actually scrambles the brain."
Inside a bear's head
Stevenson's research, like his lectures, rambles wildly, like a big-bottomed bear across a broad landscape. But stick with him, because he's on the scent, and is headed somewhere particular.
He moves on to bear sight. ("They definitely see in color, but not the way we do. We're totally visual. There's no way bears see as well as you and me.") And bear hearing. ("I think their hearing is quite good. It's nothing compared to that nose, though.") At some point, he said, he'd like to "stain" bear brain cells, so he can track sight and sound directly.
He travels to museums and to the Smithsonian, spinning tales of tracking bear skulls and bear brains from coast to coast. He dives into the cerebellum, the homunculus, the arcane reaches of creased and folded tissue.
He rumbles into the vomer-nasal passages, that curious place between smell and taste, then takes off into the frontal sinus. He stops just long enough to hand you a business card - it says only "Bear Brain Anatomy" - and then launches into the neurophysiology of mammalian auditory pathways.
"This is a whole new way of knowing the species," Stevenson says as he tucks his brain back into its clear plastic jug of formaldehyde. He stacks the picnic plates, and tucks the skulls back in their packing boxes.
"For me, this is absolutely fascinating - like getting inside a bear's head and seeing with his eyes, smelling with his nose. It gives people an idea of how they see us, which is not something people think about very much."
trib.com/news/state-and-regional/...0bf59.html
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Post by brobear on Mar 22, 2017 11:26:07 GMT -5
The grizzly is indeed the true master of survival skills among the large Carnivorans. It was a sloth of grizzlies that had wandered far to the north, became stranded, and quickly adapted to a life of hunting seals on the ice flows. Thus was born the king of the arctic; the polar bear. It is a population of grizzlies that has survived for untold thousands of years in the place nicknamed "Thirstland"... the vast Gobi Desert where the summers are intensely hot and the winters extremely cold. A desert not of sand but of stone and gravel. In the mountains are lynx and snow leopard, but only the grizzly will brave the vastness of the never-ending nothingness.
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Post by brobear on Mar 22, 2017 11:27:03 GMT -5
The Bears of Katmai by Matthias Breiter.
Bears spend as much as 60% of their lives in deep sleep, only to reappear after hibernation as if they had just undergone a slimming treatment.
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Post by brobear on Mar 24, 2017 12:03:31 GMT -5
Grizzly.
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Post by brobear on Apr 20, 2017 16:38:35 GMT -5
Date: March 25, 2014 Source: Molecular Biology and Evolution (Oxford University Press) Summary: By mining the genome of a recently sequenced polar bear, researchers developed Y chromosome-specific markers, and analyzed several regions of the Y chromosome from a broad geographic sample of 130 brown and polar bears. 'This pattern in brown bears covers even larger geographic areas than analogous findings from humans, where the Y-chromosomal lineage of Genghis Khan, founder of the Mongol Empire, was spread across much of Asia,' said experts. Male bears are seemingly always on the prowl, roaming much greater distances than females, particularly for mating. For bear evolution, studying the paternally inherited Y chromosome is therefore a rich source to trace both the geographic dispersal and genetic differences between bear species. This new study is particularly important, because a large part of our current knowledge about range-wide population structuring in mammals relies on data from maternally inherited mitochondrial DNA (mtDNA). More extensive male than female movement in bears and many other mammals implies that males carry genetic material over greater geographic distances than females. Therefore, the pronounced population structuring that has been reported for female-inherited mtDNA genes in brown bears might not be representative of the species as a whole. By mining the genome of a recently sequenced polar bear, researchers from Axel Janke´s group at the Biodiversity and Climate Research Centre in Frankfurt, Germany, developed Y chromosome-specific markers, and analyzed several regions of the Y chromosome from a broad geographic sample of 130 brown and polar bears. They also included a continuous 390,000 base pair long stretch of genomic Y chromosomal region available in brown, polar and black bear genomes to gain a better understanding of the paternal signature of bear evolution. They found evidence of extensive male gene flow that has led to the distribution of some brown bear Y chromosomes across incredibly large geographic distances, with two brown bears as far away as Norway and the Alaskan ABC islands carrying very similar Y chromosomes. This implies that one male brown bear lineage has spread across most of the brown bear's distribution range. "This pattern in brown bears covers even larger geographic areas than analogous findings from humans, where the Y-chromosomal lineage of Genghis Khan, founder of the Mongol Empire, was spread across much of Asia," said Tobias Bidon and Frank Hailer, lead authors of the study. Because their data consistently showed that black, brown and polar bears carry highly distinct Y chromosome lineages, the researchers also estimated the timing of the split between the male lineages of brown and polar bears. The obtained time estimate for the speciation event of brown and polar bears is ca. 0.4 to 1.1 million years ago. This is significantly older than previous estimates based on mtDNA, confirming recent observations from autosomal markers that brown and polar bears from a genetic point of view represent highly distinct species. The study also shows that dispersing males connect the enigmatic brown bear population of the Alaskan ABC-islands to the North American mainland, and that the resulting movement of genes is substantial enough to maintain high genetic variability within this island population. The study demonstrates that the Y chromosome represents an understudied part of the mammalian genome, providing crucial information to our understanding of the geographic structuring and evolutionary history of species. www.sciencedaily.com/releases/2014/03/140325210631.htm
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Post by brobear on Sept 27, 2018 7:36:57 GMT -5
In the Shadow of the Sabertooth by Doug Peacock. The reason grizzly remains are seldom found is probably because many of them die natural deaths in their dens. Brown bear are healthy mammals who heal well and rarely succumb to disease. They may live beyond 30 years. Human-caused mortality accounts for most modern bear deaths. Uncommonly, grizzlies are known to use caves to sleep out the winter, but suitable caves are rare and only locally available, usually in limestone topography. Before the short-faced bear succumbed to extinction 13,000 years ago, some of those caves were no doubt already occupied. So the brown bear digs dens. On rare occasion, brown bears have stayed out of the den all winter by appropriating the deer kills of cougars or elk kills of wolves - much like the short-faced bear must have scavenged his way through the Beringian darkness. But the grizzly is not an effective predator. This carnivore cannot subdue enough large animals to keep itself alive in winter. My suspicion is that most grizzly deaths in the wild take place during hibernation, a natural burial in the remote country where brown bears normally dig their dens. Back when both grizzlies and short-faced bears roamed the country, brown bears were not at the top of the food pyramid. The smaller grizzlies would be at a disadvantage trying to compete at a mammoth carcass and could not survive without denning. In coldest Beribgia, this competitive drawback could suffice to drive grizzlies south.
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Post by brobear on Sept 29, 2018 8:16:58 GMT -5
Melursus theobaldi was an ancestral bear intermediate between the grizzly and the sloth bear. This clearly explains why the sloth bear does not scurry up a tree as he is fully capable of doing. He inherited the grizzly's courage and aggressive behavior. The fact that a group of grizzlies conquered the tropical environment of India where he adapted and evolved into the sloth bear bears witness to the grizzly bear's incredible survival skills. Just as that other group of grizzlies which conquered the far arctic to evolve into the huge polar bears. The grizzly ( Ursus arctos ) is clearly the King of Bears. He survived in Europe when the giant cave bears became extinct. He survived in North America when the giant short-faced bears became extinct.
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Post by brobear on Oct 4, 2018 10:19:18 GMT -5
On the FaceBook site, Yellowstone Bears I asked this question: A grizzly spends a lot of time overturning rocks and logs. In Yellowstone. He must occasionally find a snake. Does he eat it or avoid the reptile? A - Sandy Brennan - There is no documentation of bears eating snakes, no trace has been found in bear scat. the two stories relate bears do not like snake.
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Post by Deleted on Oct 20, 2018 18:28:34 GMT -5
www.bearsmart.com/blog/7-little-known-grizzly-bear-facts/The grizzly bear hump is actually a large muscle. The most identifiable trait of a grizzly bear is the large hump on their shoulders, a powerful muscle they use to power their forelimbs through their daily routine. Grizzlies, known to dig more than any other bear species, spend inordinate amounts of time ripping through the earth and tearing apart rotted logs in search of roots, plant bulbs, insects, rodents, and other grubs. Their massive hump is also the muscle powering them as they dig out winter dens, often in steep and rocky mountain terrain.
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Post by brobear on Oct 27, 2018 4:18:54 GMT -5
www.bearsmart.com/blog/7-little-known-grizzly-bear-facts/The grizzly bear hump is actually a large muscle. The most identifiable trait of a grizzly bear is the large hump on their shoulders, a powerful muscle they use to power their forelimbs through their daily routine. Grizzlies, known to dig more than any other bear species, spend inordinate amounts of time ripping through the earth and tearing apart rotted logs in search of roots, plant bulbs, insects, rodents, and other grubs. Their massive hump is also the muscle powering them as they dig out winter dens, often in steep and rocky mountain terrain. That shoulder hump developed over roughly a million years of excavating earth reinforces the grizzly's massive upper-body strength and provides for him a devastating paw-strike.
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