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Post by brobear on Apr 22, 2022 1:35:38 GMT -5
This study about size, diet, and extinction is quite interesting. A good read. But here, I am focusing on omnivores. www.sciencedaily.com/releases/2022/04/220421131006.htm Quote: It's been several decades since ecologists realized that graphing the diet-size relationship of terrestrial mammals yields a U-shaped curve when aligning those mammals on a plant-to-protein gradient. As illustrated by that curve, the plant-eating herbivores on the far left and meat-eating carnivores on the far right tend to reach sizes much larger than those of the all-consuming omnivores and the invertebrate-feasting invertivores in the middle. *However, the omnivorous bears tend to be larger than any land-based pure carnivore.
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Post by OldGreenGrolar on Apr 22, 2022 3:08:34 GMT -5
/\ I think it depends. Most brown bears are heavier than all extinct cats. However, sloth bears, Asiatic black bears, and most American black bears (save a few exceptionally large specimens) are smaller than Bengal tigers, Siberian tigers, and African lions.
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Post by brobear on Apr 22, 2022 3:28:23 GMT -5
/\ I think it depends. Most brown bears are heavier than all extinct cats. However, sloth bears, Asiatic black bears, and most American black bears (save a few exceptionally large specimens) are smaller than Bengal tigers, Siberian tigers, and African lions. Yes, there are some bears smaller than the biggest cats. However, when you look at cats and bears in general, then size leans in favor of the bears.
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Post by brobear on Apr 22, 2022 5:18:35 GMT -5
Omnivores: Facts About Flexible Eaters www.livescience.com/53483-omnivores.html 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 May 5, 2022 17:57:18 GMT -5
10 Animals That Are Omnivores www.worldatlas.com/articles/10-animals-that-are-omnivores.html Omnivores are animals that can consume and survive on both animal and plant matter. These animals obtain nutrients and energy from both animals and plants. Omnivores can also incorporate other food sources like bacteria, fungi, and algae in their diet. Omnivores can digest fibers, fats, proteins, and carbohydrates. Omnivores are opportunist feeders that are not related anatomically. Omnivores are widespread across numerous taxonomic clades. Some of the animals that are omnivores include: 1- Pigs Pigs are omnivores belonging to a family of even-toed ungulate known as Suidae and the genus Sus. Pigs are indigenous to the African and Eurasian continents. Pigs include all the domesticated pigs and the Eurasian wild swine together with other species. Some of the related creatures outside the genus Sus include warthogs, the babirusa, and the peccary. Pigs are intelligent and social animals that are biologically similar to human beings. Pigs evolved from the Artiodactyla (a herbivorous creature). Wild pigs are foraging creatures that feed on flowers, fruits, roots, and leaves, among others. Feral pigs also feed on fish and insects. As livestock, they feed on soybean and cornmeal, with a mixture of minerals and vitamins. 2- Dogs Domesticated dogs (Canis familiaris when they are considered to be a distinct species or Canis lupus familiaris when they are classified as a subspecies of the gray wolves) belong to the genus Canis. The gray wolves and dogs are sister taxa. Genetic divergence between the wolves and dogs took place about 40,000years ago during or right before the Last Glacial Maximum. Dogs were the first animal species to be domesticated, and they have been selectively bred over the years for their physical attributes, sensory capabilities, and various behaviors. Dogs are omnivores and compared to other wolves; they have genes that help them digest starch. Many people consider dogs to be carnivorous; however, based on their nutrition and metabolism, they are omnivores. 3- Bears Bears are grouped as doglike carnivorans or caniforms, and they belong to the family Ursidae. Even though there are only 8 extant bear species, bears can be found in a wide range of terrains all over the northern hemisphere. Bears are opportunistic omnivores that consume more plants than meat. Bears consume anything from berries, roots, and leaves to fish, fresh meat, carrion, and insects. Bears consume anything that is seasonally available. Bears don't feed on older leaves, sedges, and grasses. Bears consume plants when they are more digestible and nutritious. Asiatic black bears consume ungulates and a considerable number of acorns. 4- Coatis A coati is a diurnal mammal that is indigenous to Mexico, the United States, Central America, and South America. Coatis, also referred to as hog-nosed coon or coatimundi, belongs to the family Procyonidae. Coatimundis are omnivores, and their diet is mainly composed of invertebrates like a tarantula, ground litter, and fruits. Coatimundis also consume smaller vertebrates like small birds, rodents, and lizards. 5- Hedgehogs Hedgehogs are spiny mammals that belong to the subfamily Erinaceinae. There are 17 hedgehog species in 5 genera found in Africa, Asia, and Europe. Hedgehogs are nocturnal creatures that protect themselves using the spines on their bodies. Hedgehogs feed on watermelon, berries, grassroots, mushrooms, bird eggs, snakes, toads, snails, and insects. 6- Opossum Opossums are marsupials that are indigenous to the Americas. Opossums belong to the order Didelphimorphia with the only species found in the United States and Canada being the Virginia opossums. Their unique reproductive habit, flexible diet, and unspecialized biology make them successful survivors in diverse conditions and places. Opossums are omnivores that feed on dead animals, birds, rodents, and insects. They also consume grains, frogs, plants, fruits, and eggs. 7- Chimpanzees Chimpanzees are great ape species that are native to the savannas and forests of tropical Africa. All hominids, including chimpanzees, are omnivorous. Chimpanzees prefer fruits over all the other foods, but they can also consume stems, blossoms, seeds, leaf buds, and leaves. Even though chimpanzees are mostly herbivorous, they can also eat birds, insects, small-to-medium-sized animals, and honey. Some of the insects consumed by chimpanzees include honey bees, termites, and weaver ants. Other preys include common warthogs, yellow baboons, blue duikers, and red-tailed monkeys. 8- Squirrels Squirrels belong to the family Sciuridae, and they are native to Africa, Eurasia, and the Americas. Squirrels were introduced in Australia by human beings. Some of the members of the squirrel family include prairie dogs, ground squirrels, flying squirrels, chipmunks, and marmots, among others. Squirrels prefer foods rich in fats, carbohydrates, and proteins since their bodies cannot digest cellulose. Squirrels consume conifer cones, seeds, fruits, nuts, green vegetables, fungi, small rodents, young snakes, insects, and small birds, together with bird eggs. 9- Raccoons Raccoons also referred to as northern raccoons, or coon, are medium-sized mammals that can be found in North America. Raccoons are the largest members of the procyonid family with a bodyweight of about 57pounds and a maximum body length of approximately 28inches. Raccoons are nocturnal creatures that are sometimes active during the daytime. The Raccoon's diet is composed of vertebrates (27%), plant material (33%), and invertebrates (40%). Raccoon's diet, during early summer and spring, is made up of worms, insects, and other animals. Raccoons consume various nuts, including walnuts and acorns, which thrive in autumn and late summer. Raccoons are known predators of hatchlings and eggs in reptile and bird nests. 10- Chipmunks A chipmunk is a small striped rodent belonging to the Sciuridae family. All Chipmunks are native to North America except the Siberian chipmunks that can be found in Asia. Chipmunks are omnivores, and their diet is made up of nuts, seeds, buds, grass, and shoots, among other plants. Chipmunks also feed on bird eggs, worms, small frogs, insects, and fungi. Chipmunks are considered to be pests since they consume cultivated vegetables and grains among other plants in the gardens and farms.
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Post by brobear on Oct 30, 2022 5:46:42 GMT -5
All Bears are Omnivores Like Humans, New Study Suggests Oct 3, 2022 www.sci.news/biology/omnivorous-bears-11253.html New research on the diets of giant pandas (Ailuropoda melanoleuca) and sloth bears (Melursus ursinus) adds evidence that bears are low-protein macronutrient omnivores and need a lot less protein than they are typically fed in zoos. “Bears are not carnivores in the strictest sense like a cat where they consume a high-protein diet,” said Washington State University’s Professor Charles Robbins. “In zoos forever, whether it’s polar bears, brown bears or sloth bears, the recommendation has been to feed them as if they are high-protein carnivores. When you do that, you kill them slowly.” In their experiments, Professor Robbins and colleagues presented captive giant pandas and sloth bears at different U.S. zoos with unlimited food of different types to see their preferences and then recorded the nutritional profiles of their choices. They conducted feeding trials with a pair of giant pandas to measure their bamboo selection. They found that the pandas preferred the carbohydrate-rich bamboo culm found in the woody stalks, over the more protein-rich leaves. At some points, the animals consumed culm almost exclusively — for instance 98% of the time in the month of March. The researchers also analyzed data from five zoos in China which had giant pandas that had successfully reproduced and found again, a high-carbohydrate, low-protein diet. In sets of feeding trials, six sloth bears at the Cleveland, Little Rock and San Diego zoos, were presented with unlimited avocados, baked yams, whey and apples. They chose the fat-rich avocados almost exclusively, eating roughly 88% avocadoes to 12% yams — and ignoring the apples all together. This showed sloth bears preferred a high-fat, low-carbohydrate diet, which may have a similar makeup to their wild diet of termites and ants as well as their eggs and larvae. It’s also vastly different than the high-carbohydrate diet they are usually fed in captivity. Sloth bears, which are native to India, typically live only around 17 years in U.S. zoos, almost 20 years less than the maximum lifespan achievable in human care. Their most frequent cause of death is liver cancer. The researchers saw a similar pattern in previous studies of polar bears that showed captive polar bears, who are normally fed a high-protein diet, would mimic the fat-rich diet of wild polar bears if given the option. Polar bears in zoos typically die about 10 years earlier than they should, most often of kidney and liver disease. These two diseases can develop from long-term inflammation of those organs, potentially caused by many years of poorly balanced diets. The current study, along with previous ones, also shows that when captive bears are given dietary options, they will choose foods that imitate the diets of wild bears. “All of these bears started evolving about 50 million years ago, and in terms of this aspect of their diet, they know more about it than we do. We’re one of the first to be willing to ask the bears: What do you want to eat? What makes you feel well?” Professor Robbins said. The findings appear in the journal Scientific Reports. All Bears are Omnivores.
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Post by brobear on Oct 30, 2022 5:57:34 GMT -5
Increasing evidence that bears are not carnivores Given a choice, captive bears mimic mixed diets of wild peers Date: October 3, 2022 Source: Washington State University www.sciencedaily.com/releases/2022/10/221003090605.htm Bears are not cats or dogs, and feeding them like they are likely shortens their lives. A new study on the diets of giant pandas and sloth bears adds more evidence that bears are omnivores like humans and need a lot less protein than they are typically fed in zoos. Bears are not cats or dogs, and feeding them like they are likely shortens their lives. A new study in Scientific Reports on the diets of giant pandas and sloth bears adds more evidence that bears are omnivores like humans and need a lot less protein than they are typically fed in zoos. "Bears are not carnivores in the strictest sense like a cat where they consume a high-protein diet," said lead author Charles Robbins, a Washington State University wildlife biology professor. "In zoos forever, whether it's polar bears, brown bears or sloth bears, the recommendation has been to feed them as if they are high-protein carnivores. When you do that, you kill them slowly." In separate experiments, researchers presented captive giant pandas and sloth bears at different U.S. zoos with unlimited food of different types to see their preferences and then recorded the nutritional profiles of their choices. In collaboration with researchers from Texas A&M University and the Memphis Zoo, feeding trials were conducted with a pair of giant pandas to measure their bamboo selection. They found that giant pandas preferred the carbohydrate-rich bamboo culm found in the woody stalks, over the more protein-rich leaves. At some points, they consumed culm almost exclusively -- for instance 98% of the time in the month of March. The researchers also analyzed data from five Chinese zoos which had giant pandas that had successfully reproduced and found again, a high-carbohydrate, low-protein diet. In sets of feeding trials, six sloth bears at the Cleveland, Little Rock and San Diego zoos, were presented with unlimited avocados, baked yams, whey and apples. They chose the fat-rich avocados almost exclusively, eating roughly 88% avocadoes to 12% yams -- and ignoring the apples all together. This showed sloth bears preferred a high-fat, low-carbohydrate diet, which may have a similar makeup to their wild diet of termites and ants as well as their eggs and larvae. It's also vastly different than the high-carbohydrate diet they are usually fed in captivity. Sloth bears, which are native to India, typically live only around 17 years in U.S. zoos, almost 20 years less than the maximum lifespan achievable in human care. Their most frequent cause of death is liver cancer. Researchers saw a similar pattern in previous studies of polar bears that showed captive polar bears, who are normally fed a high-protein diet, would mimic the fat-rich diet of wild polar bears if given the option. Polar bears in zoos typically die about 10 years earlier than they should, most often of kidney and liver disease. These two diseases can develop from long-term inflammation of those organs, potentially caused by many years of poorly balanced diets. The current study, along with previous ones, also shows that when captive bears are given dietary options, they will choose foods that imitate the diets of wild bears. "There's certainly this long-standing idea that humans with Ph.D.s know a lot more than a sloth bear or a brown bear," said Robbins. "All of these bears started evolving about 50 million years ago, and in terms of this aspect of their diet, they know more about it than we do. We're one of the first to be willing to ask the bears: What do you want to eat? What makes you feel well?" Robbins, the founder of the WSU Bear Center, the only research institution in the U.S. with a captive population of grizzlies, has studied bear nutrition for decades. He and his graduate students first started investigating their misbalanced diets during a study in Alaska, watching grizzlies eat salmon. At the time, the researchers had theorized that the notoriously voracious bears would gorge on salmon, sleep, get up and eat more salmon. Instead, they saw the bears would eat salmon, but then wander off and spend hours finding and eating small berries. Seeing that, Robbins' laboratory started investigating diet with the grizzly bears housed at the Bear Center and found they gained the most weight when fed a combination of protein, fats and carbohydrates in the combination of salmon and berries. All eight types of bears, or Ursids, had a carnivore ancestor but have since evolved to eat a wide array of food, which gave them the ability to spread into more areas by not directly competing with resident carnivores. "It just opens up so many more food resources than just being a straight, high protein carnivore," Robbins said.
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Post by brobear on Dec 10, 2022 6:46:53 GMT -5
All Bears are Omnivores Like Humans, New Study Suggests Oct 3, 2022 www.sci.news/biology/omnivorous-bears-11253.html New research on the diets of giant pandas (Ailuropoda melanoleuca) and sloth bears (Melursus ursinus) adds evidence that bears are low-protein macronutrient omnivores and need a lot less protein than they are typically fed in zoos. “Bears are not carnivores in the strictest sense like a cat where they consume a high-protein diet,” said Washington State University’s Professor Charles Robbins. “In zoos forever, whether it’s polar bears, brown bears or sloth bears, the recommendation has been to feed them as if they are high-protein carnivores. When you do that, you kill them slowly.” In their experiments, Professor Robbins and colleagues presented captive giant pandas and sloth bears at different U.S. zoos with unlimited food of different types to see their preferences and then recorded the nutritional profiles of their choices. They conducted feeding trials with a pair of giant pandas to measure their bamboo selection. They found that the pandas preferred the carbohydrate-rich bamboo culm found in the woody stalks, over the more protein-rich leaves. At some points, the animals consumed culm almost exclusively — for instance 98% of the time in the month of March. The researchers also analyzed data from five zoos in China which had giant pandas that had successfully reproduced and found again, a high-carbohydrate, low-protein diet. In sets of feeding trials, six sloth bears at the Cleveland, Little Rock and San Diego zoos, were presented with unlimited avocados, baked yams, whey and apples. They chose the fat-rich avocados almost exclusively, eating roughly 88% avocadoes to 12% yams — and ignoring the apples all together. This showed sloth bears preferred a high-fat, low-carbohydrate diet, which may have a similar makeup to their wild diet of termites and ants as well as their eggs and larvae. It’s also vastly different than the high-carbohydrate diet they are usually fed in captivity. Sloth bears, which are native to India, typically live only around 17 years in U.S. zoos, almost 20 years less than the maximum lifespan achievable in human care. Their most frequent cause of death is liver cancer. The researchers saw a similar pattern in previous studies of polar bears that showed captive polar bears, who are normally fed a high-protein diet, would mimic the fat-rich diet of wild polar bears if given the option. Polar bears in zoos typically die about 10 years earlier than they should, most often of kidney and liver disease. These two diseases can develop from long-term inflammation of those organs, potentially caused by many years of poorly balanced diets. The current study, along with previous ones, also shows that when captive bears are given dietary options, they will choose foods that imitate the diets of wild bears. “All of these bears started evolving about 50 million years ago, and in terms of this aspect of their diet, they know more about it than we do. We’re one of the first to be willing to ask the bears: What do you want to eat? What makes you feel well?” Professor Robbins said. The findings appear in the journal Scientific Reports. As an omnivore, a bear is a mixture of herbivore (grazer, browser, and a digger for roots), insectivore, piscivore, and carnivore (predator, scavenger, and kleptoparasite). Such a huge variety of food resources makes the bear a "jack-of-all-trades" and an intelligent survivor.
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Post by brobear on Feb 13, 2023 3:12:52 GMT -5
The Life of Mammals by David Attenborough. 2002. 6- The Oppotunists. Bamboo is one of the most indigestible members of a markedly indigestible plant family. It is a giant grass. All grasses require particularly strong teeth to grind them and capacious stomachs, sometimes with special compartments, to digest them. Those mammals that developed such things and cropped grasses on the open plains of the world now flourish in vast numbers. But bamboo presents particular problems. It grows fifty feet tall and more. It is exceptionally tough and woody. Mature stems are so heavily impregnated with silica that they will blunt the sharpest and the strongest steel knife. Only its young shoots can be considered remotely edible. In consequence very few animals feed on bamboo. That means that any species that succeeds in doing so has vast quantities of food at its disposal. And that, it seems, is a great evolutionary inducement.
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Post by brobear on Feb 13, 2023 3:25:22 GMT -5
The giant panda's ancestors responded. Today the panda has large molar teeth that are flattened for crushing and grinding. Even the teeth that in cats are sharpened into carnassials, are shaped in this way. And it has a special device for harvesting the bamboo stems. No animal, except monkeys and apes, have thumbs that can bend towards other digits and so give a hand grasp. Except for the giant panda. One of its wrist bones has become modified to form a projection, fully muscled and mobile, at the base of its front paw. This, in effect, gives it six digits on each of its front feet. By pressing this pseudo-thumb against the main pad of its foot, the panda can grip a young stem of bamboo and feed it into its mouth in the same way as one might eat celery.
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Post by brobear on Feb 13, 2023 3:46:39 GMT -5
But linking oneself so closely to a restricted diet is a risky thing to do. If for some reason that food disappears, an animal may be so specialized that it cannot switch to a diferent food and therefore starves. Bamboo has another unhelpful characteristic apart from its indigestibility. Some species flower only very rarely and extend their range instead by sending shoots from the root-like rhizomes. But, eventually, they do flower and all individual clumps of the same species do so simultaneously. Sometimes the period between flowering is fifteen years. In others, it can be as long as a hundred and twenty. But after a species has flowered, all mature plants die. Its future now rests entirely in its seeds. If pandas were feeding in a forest of such bamboo, they would have to migrate after a mass flowering to find a different species. That, at best of times, must have given giant pandas a recurring and serious problem. These days however, the increase in the human population of China has led to extensive felling of the bamboo forest. Few patches remain for pandas compared with only a century ago. If the bamboo in one of these small isolated sanctuaries dies off, the pandas - left to themselves - will die off too. It is hardly surprising that today the giant panda is one of the most endangered of all mammals. Specialism is a high-wire act - spectacular when it is successful but catastrophic if there is one small failure.
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Post by brobear on Feb 13, 2023 5:24:22 GMT -5
Yet it is possible for n animal to survive on food that appears only briefly and spasmodically if it is prepared - behaviourally, dentally, and digestively - to eat a great variety of widely different things. It can then feast on one food while that happens to be available and when that disappears, move on to find a different one. That is the way of the omnivore and it was the one followed by most of the other members of the giant panda's family, the bears.
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Post by brobear on Feb 13, 2023 5:32:28 GMT -5
The biggest bear of all, the grizzly, lives in the far north of America. It is another of those species that has adapted to a cold climate by growing huge and thus conserving its body heat. The grizzly is immense. A big male can weigh over half a ton. It is also extremely fast and can easily outrun a man. Such a stature, strength, and speed make it a formidable hunter and grizzlies will kill mountain sheep and moose, the biggest of all deer. But prey of any kind can be energy consuming to find and kill, so meat is by no means the major element in their diet. In spring they eat all kinds of vegetation - grass, horsetails, skunk cabbage, and lily roots. They wander down to the sea-shore and they scoop up molluscs from the sand. In summer they dine on elderberries and cranberries. They also dig out mice, squirrels, and marmots from their burrows.
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Post by brobear on Feb 13, 2023 6:07:44 GMT -5
When the salmon start to migrate up Alaska's rivers, the bears gather beside falls and rapids, often in groups of a dozen or more, in places where they know that the salmon will have to leap in order to continue up-river and reach their spawning grounds. There, with great dexterity and perfect timing, the grizzlies snatch the jumping fish from the air. The rewards can be so great that in those special places where fish leap in great numbers, dozens of bears that normally avoid one another will gather together beside the falls and catch fish in their jaws without even moving.
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Post by brobear on Feb 13, 2023 6:21:20 GMT -5
The bears that live in Yellowstone have discovered a particular delicacy. In July, cutworm moths appear in thousands to feed at night on the summer flowers. During the day, they hide under rocks but the bears have discovered them and regularly climb up to atitudes of 10,000 feet in order to feast on them. A single bear in a single day will lick up 30,000.
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Post by brobear on Feb 13, 2023 6:38:12 GMT -5
But a big animal has a big appetite. That is one of the disadvantages of size and even such an unfussy omnivore as a grizzly may find it hard to get enough to eat. So grizzlies forage alone. When winter comes and the land is covered with a blanket of snow, even the enterprising and open-minded grizzly cannot find sufficient food to sustain itself. It solves the problem by going to sleep. Each bear, by itself, finds a cave or a hollow tree and settles down for slumber. Its bodily processes begin to slow. Its temperature drops several degrees and its pulse drops to about ten beats per minute. It becomes very drowsy. For the next five months it fuels its body from its fat reserves and does not eat or drink, urinate or defecate. This is not true hibernation like that of marmots, ground squirrels and other rodents, whose heart-beat at such times slows to almost imperceptible levels and whose temperature falls to within a degree or so of freezing. Such hibernation take considerable time to return to full activity. But it could be a serious mistake to suppose that sleeping bears in winter would behave in the same way. They can, if disturbed, rouse themselves instantly.
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Post by brobear on Feb 13, 2023 7:16:10 GMT -5
A female bear, hoever, may do more than sleep during the winter months. Even as she dozes, she gives birth. One, or more usually two, small naked cubs slip from her body. They are no bigger than rats, extraordinarily small compared with her huge bulk. A new born human baby, which seem so minuscule to its parents, weighs about one fifteenth as much as its mother. The new born grizzly is only about one hundredth. It is smaller, in proportion to the size of its mother than the young of any other placental mammal. But its tiny stature and total helplessness matters little, for here in a den in the middle of winter, in the furry embrace of its gigantic and powerful mother, nothing is likely to harm it.
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Post by brobear on Feb 13, 2023 8:19:52 GMT -5
For four or five months, the cubs remain with her in the darkness of the den, nourished by her milk and steadily growing. As the weeks pass, their eyes open, their fur appears and they grow bigger. Outside, the snow melts. And then, as spring arrives, the mother and her young emerge into the sunlight. Now the cubs must eat something other than milk. At first, there are fresh green leaves and buds to eat, but as spring proceeds and temperatures begin to rise, new foods appear. Even intelligent and inquisitive young omnivores have to be taught about what can be found where, what is good to eat and what should be avoided. As each new crop appears, the mother grizzly guides her cubs to it. So they learn a precise sequence for their foraging. They will stay with her for another year or even two and go through the whole sequence again. After that they are on their own.
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Post by brobear on Feb 13, 2023 8:46:21 GMT -5
Farther north still, another bear, the white furred polar bear is not quite so open-minded about what it eats. An adult female behaves in much the same way as the female grizzly. When winter comes, she digs a den in the snow and there produces her cubs - again usually twins. She has little alternative, for her tiny naked young could hardly survive out in the open with temperatures dropping to 30 degrees C (86 Degree Fahrenheit) below freezing. The males, however, have no such compulsion for they take no part in caring for the cubs. Indeed, there is every reason for them to remain active for there is a lot of food to be had out on the arctic sea-ice.
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Post by brobear on Feb 13, 2023 12:32:19 GMT -5
Seals must breathe and throughout the winter they have to maintain holes in the ice where they can do so. A seal's breath certainly has a strong smell, but even so bears can detect it from extraordinarily long distances. They can identify the odour of a breathing hole from up to three miles away, even if it is buried beneath three feet of wind-blown snow. The bear will wait patiently beside such a hole and when the seal eventually appears, it uses its fore-paws to strike with such power that it may shatter the seal's skull. The seals are particularly vulnerable when breeding begins - from February onwards. The females haul themselves out alongside their holes and give birth usually in small chambers hollowed out beneath the snow. Bars are expert in locating these. They creep slowly towards them. If the female seal detects the hunter's approach she will slide down into the water and escape, but her pup for the first few days of its life, cannot swim. The bear rears up on its hind legs and brings its fore-feet down on the little cavern with devastating force. The pup is killed instantly. Male polar bears are well-fed throughout the winter.
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