BEARS: HISTORY, EVOLUTION, HABITAT, PIZZLIES

BEARS

1) Giant Panda (Ailuropoda melanoleuca), 2) Andean Bear (Tremarctos ornatus), 3) Sun Bear (Helarctos malayanus), 4) Sloth Bear (Melursus ursinus), 5) Asiatic Black Bear (Ursus thibetanus), 6) American Black Bear (Ursus americanus)

Bears are the world's largest carnivores (polar bears and brown bears are bigger than Siberian tigers and lions, the next largest carnivores) but are technically omnivores (eat plants and animals) that get most of the nutrients from berries, leaves, roots, and other kinds of vegetation, and are only partly carnivorous.

There are eight species of bears: 1) sloth bears of the Indian subcontinent; 2) sun bears (also known as Malayan bears) of southern Asia; 3) Asiatic black bears (moon bears) of Asia; 4) polar bears of the Arctic (which evolved from brown bears a couple million years ago; 5) brown bears of North America, Asia and Europe (Grizzlies and Kodiak bears are kinds of brown bears); 6) black bears of North America; 7) Spectacled bears (Andiean bears) of South America; and 8) Giant Pandas.

Whether or not pandas are bears is a matter of debate but these days most scientists do regard them as bears. Red pandas are not classified as Ursidae. Relatively little is known about some of the bear species and subspecies in Asia and South America.

Bears belong to the Carnivora order, Ursidae family and Ursus genus. There are three existing subfamiles: Ailuropodinae (pandas), Tremarctinae (short-faced bears) and Ursinae (all other bear species). Males are known as boars and females are called sows and young are called cubs. A group of bears is called a "sloth." You don’t see groups very often. There are around 700,000 black bears and 70,000 brown bears and grizzly bears in North America. DNA studies have show that some brown bears are more closely related to polar bears than they are to other brown bears.

Websites and Resources on Animals: Bear Conservation bearconservation.org ; Bear Book and Curriculum Guide web.archive.org ; Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org

Books: “Bears: Majestic Creatures of the Wild” edited by Ian Stirlin (Rodale Press); Book: “Bears: A Brief History” by Bernd Brunner (Yale University Press, 2008); “Bears of the World” by Terry Domico and Mark Newman (1988)

Early Bear Evolution

Kolponomos newportensis (an
Amphicynodontinae)

All bears are thought to have descended from an animal about the size of a beagle. Darwin hypothesized that bears “could one day evolve into completely aquatic creatures.” The fossil record of bears in North America and Eurasia extends to the (late Eocene to early middle Miocene, 38–18 million years ago). It is thought that bears reached Africa in the Late Miocene Period (11.6 million to 5.3 million years ago) and South America in the Early Pleistocene Period (2.6 million to 800,000 years ago). [Source: Tanya Dewey and Phil Myers, Animal Diversity Web (ADW) /=]

The earliest members of Ursidae belong to the extinct subfamily Amphicynodontinae, including Parictis (late Eocene to early middle Miocene, 38–18 million years ago) and the slightly younger Allocyon (early Oligocene, 34–30 million years ago), both from North America. These animals looked very different from today's bears. They were relatively small and looked sort of like raccoons or otters and had diets perhaps similar to those of badgers. Parictis did not appear in Eurasia and Africa until the the Early Miocene Period (23 million to 16 million years ago). There is some morphological and molecular evidence linking early bear ancestors with pinnipeds (seals and sea lions), as both groups were semi-aquatic, otter-like mammals. [Source: Wikipedia]

The raccoon-sized, dog-like Cephalogale is the oldest-known member of the subfamily Hemicyoninae, which first appeared during the middle Oligocene in Eurasia about 30 million years ago. This subfamily includes the younger genera Phoberocyon (20–15 million years ago), and Plithocyon (15–7 million years ago). A Cephalogale-like species gave rise to the genus Ursavus during the early Oligocene (30–28 million years ago); this genus proliferated into many species in Asia and is ancestral to all living bears. Species of Ursavus subsequently entered North America, together with Amphicynodon and Cephalogale, during the early Miocene (21–18 million years ago). Members of the living lineages of bears diverged from Ursavus between 15 and 20 million years ago, likely via the species Ursavus elmensis.

Cave Bear

evolution of different bear species, from Researchgate

The cave bear was a European species that coexisted with early humans for about 20,000 years before dying out about 25,000 years ago. Both the word "cave" and the scientific name spelaeus are used because fossils of this species were mostly found in caves. This reflects the views of experts that cave bears may have spent more time in caves than the brown bear, which uses caves only for hibernation. There were several species of cave bear, including the small cave bear (Ursus rossicus) and large cave bear (Ursus spelaeus). Both could be found across Eurasia during the last ice age. Small cave bears resembled modern-day brown bears in size. [Source: Wikipedia]

According to Live Science Fossils of cave bears show they were closely related to brown bears (Ursus arctos) and polar bears (Ursus maritimus), grew to around 3.5 meters (11.5 feet) tall and weighed a whopping 1,500 kilograms (3,300 pounds). U. spelaeus went extinct around 22,000 years ago, toward the end of the Last Glacial Maximum, the coldest part of the last ice age. [Source: Harry Baker, Live Science, March 3, 2023]

Andrew Curry wrote in Smithsonian Magazine: “People have been excavating cave bear remains for hundreds of years—in the Middle Ages, the massive skulls were attributed to dragons—but the past decade has seen a burst of discoveries about how the bears lived and why they went extinct. An abundance of bear bones has been found from Spain to Romania in caves where the animals once hibernated. “Caves are good places to preserve bones, and cave bears had the good sense to die there,” Hervé Bocherens, an evolutionary biologist at the University of Tübingen, Germany, says. [Source: Andrew Curry, Smithsonian Magazine, December 2010]

Evolution of Today's Bear Species

Based on genetic and morphological data, the Ailuropodinae (pandas) were the first to diverge from other living bears about 19 million years ago, although no fossils of this group have been found before about 11 million years ago. The New World short-faced bears (Tremarctinae) differentiated from Ursinae following a dispersal event into North America during the mid-Miocene (about 13 million years ago). They entered South America 2.5 to million years ago following formation of the Isthmus of Panama. Their earliest fossil representative — the genus Plionarctos in North America (10–2 million years ago) — is probably the direct ancestor to the North American short-faced bears (genus Arctodus), the South American short-faced bears (Arctotherium), and the spectacled bears, the lone surviving representative of the Tremarctinae subfamily.

Size chart depicting the extant and extinct species of the family Tremarctinae (short-faced bear)

The subfamily Ursinae experienced a dramatic proliferation of taxa about 5.3–4.5 million years ago that coincided with major environmental changes. The first members of the genus Ursus appeared around this time. The sloth bear is a modern survivor of one of the earliest lineages to diverge, around 5.3 million years ago, and acquired peculiar morphology adapted to eating termites and ants, no later than by theEarly Pleistocene Period (2.6 million to 800,000 years ago).

By 3–4 million years ago, the species Auvergne bear (Ursus minimus) appears in the fossil record of Europe; apart from its size, it was nearly identical to today's Asian black bear. It is likely ancestral to all bears within Ursinae, perhaps aside from the sloth bear. Two lineages evolved from Auvergne bear: the black bears (including sun bears, Asian black bears, and American black bears); and brown bears (which includes the polar bear). Modern brown bears evolved from Auvergne bears via the Etruscan Bears (Ursus etruscus), which is also an ancestor to the extinct Pleistocene cave bear.

Species of Ursinae migrated repeatedly into North America from Eurasia as early as 4 million years ago during the early Pliocene. The polar bear is the most recently evolved species and descended from a population of brown bears that became isolated in northern latitudes by glaciation 400,000 years ago.Prehistoric North and South American short-faced bears were the largest species known to have lived. The latter estimated to have weighed 1,600 kg (3,500 lb) and stood 3.4 meters (11 feet) tall. .

Bear Habitat and Where They Are Found

There are no bears in Australia, Africa or Antarctica. Otherwise bears are found on all the other continents. There are brown bears in the Himalayas, northern China, Mongolia, Central Asia, Japan, Russia and Europe. There are no black bears (except black brown bears) in Europe and most of Central Asia and much of Russia. Asiatic black bear (Ursus thibetanus) can found in a few places in Pakistan, Afghanistan and Iran as well as in the Russian Far East, particularly in the Khabarovsk Territory, Maritime Territory, and southern Yakutia. In those parts of Russia they are also known as the Ussuri black bear.

Bears are primarily found throughout the northern hemisphere, historically occurring as far south as the Atlas Mountains of northwestern Africa, the Andes of South America, and the Sunda shelf region between Malaysia and Indonesia in Asia. This range has shrunk in historical times as a result of human persecution and habitat destruction. For example, brown bear (Ursus arctos) populations in the Atlas Mountains are thought to be extinct and their range has been significantly altered in North America and Europe. [Source: Tanya Dewey and Phil Myers, Animal Diversity Web (ADW) /=]

Bears occur in nearly all terrestrial habitats throughout their range, from Arctic tundra and polar ice floes to tropical and temperate forests, mountains, grasslands, and deserts. Although some bear species occur in arid areas, proximity to water is important. Bears are most abundant and diverse in temperate and boreal regions. Most species are habitat generalists, changing preferred foods, activity patterns, and denning quarters with local conditions. Giant pandas, however, are found primarily in the montane bamboo forests of southern China./=\

Many of the countries where Asian bears live are too poor to carry out studies or conduct conservation efforts. This is one reason why little is known about them and their populations are threatened by human activities. The governments of countries inhabited by these bears are sometimes assisted by the International Union for Conservation of Nature (IUCN), the World Wildlife Fund and other groups in their conservation efforts.

Large Carnivores Help Ecosystems

Simon Sturdee of AFP wrote: As a "keystone species", big predators are important players in ecosystems, having hugely beneficial and sometimes surprising trickle-down effects. In a famous example in the Yellowstone National Park in the United States, the reintroduction of wolves in the 1990s led deer and their other prey to avoid open areas more. This in turn allowed vegetation, which the deer would otherwise eat, to thrive, providing not just cover and food for other animals but even, by firming up the soil, slowing erosion by waterways. In the case of bears, the WWF says, they play an important role keeping other animal populations in check and also in "seed dispersal" from their droppings. [Source: Simon Sturdee, AFP November 16, 2014]

In January 2014, AFP reported: “The gradual decline of large carnivores such as lions, wolves or pumas is threatening the Earth's ecosystems, scientists warned as they launched an appeal to protect such predators. More than 75 per cent of 31 large carnivore species are on the decline, and 17 of them now occupy less than half of their former ranges, says a study published in the American journal Science. [Source: AFP, January 10, 2014]

"Globally, we are losing large carnivores," wrote William Ripple, lead author of the study and a professor in the Department of Forest Ecosystems and Society at Oregon State University. "Many of them are endangered," Ripple wrote. "Their ranges are collapsing. Many of these animals are at risk of extinction, either locally or globally. And, ironically, they are vanishing just as we are learning about their important ecological effects."

“Ripple and his colleagues reviewed published scientific reports and focused on seven species that have been studied for their widespread ecological effects. They are African lions, leopards, Eurasian lynx, cougars, gray wolves, sea otters and dingoes. The different reports show that a decline in pumas and wolves in Yellowstone National Park led to an increase in animals that feed on tree leaves and bushes, such as deer and elk. This disrupts the growth of vegetation and shifts populations of birds and small mammals, the researchers said.

In Europe, fewer lynx have been tied to overpopulation of roe deer, red foxes and hares, while in Africa the disappearance of lions and leopards has coincided with a dramatic increase in the number of olive baboons, which threaten farm crops and livestock. In Alaska, a decline in sea otters through killer whale depredation has triggered a rise in sea urchins and loss of kelp beds.

"Nature is highly interconnected," said Ripple. "The work at Yellowstone and other places shows how one species affects another and another through different pathways." For instance, avoiding overpopulation of herbivores allows forest flora to develop more and sequester more carbon dioxide, the main green house gas responsible for global warming. But the authors of the study say it will be very hard to convince people to accept a large scale restoration of large carnivore populations. People are afraid of them and have fought them to protect their livestock and their communities, they said.

Pizzly Bears and Grolars

When a polar bear (Ursus maritimus) and a grizzly bear (Brown bears horribilis) mate, they can create hybrids called "pizzly" or "grolar" bears. According to Live Science: Although rare in nature, these pizzly bear hybrids are starting to spread across the Arctic due to climate change. Starving polar bears are heading farther south to find more food, while the warming world is allowing adaptable grizzlies to expand northward. This movement is leading to more interactions between the two species and more mating. [Source: Patrick Pester, Live Science, October 25, 2023]

In 2006, Roger Kuptana, an Inuit tracker from the Northwest Territories, Canada guided an American hunter who shot a pizzly == the first documented case of a grizzly-polar hybrid in the wild. Associated Press reported: Territorial officials seized the bear’s body and a DNA test from Wildlife Genetics International, a lab in British Columbia, confirmed the hybrid was born of a polar bear mother and grizzly father. “It’s something we’ve all known was theoretically possible because their habitats overlap a little bit and their breeding seasons overlap a little bit,” said Ian Stirling, a biologist with the Canadian Wildlife Service in Edmonton, Alberta. “It’s the first time it’s known to have happened in the wild.” He said the first person to realize something was different about the bear — shot and killed last month on the southern end of Banks Island in the Beaufort Sea — was Kuptana. “These guides know their animals and they recognized that there were a number of things that didn’t look quite right for a polar bear,” Stirling told The Associated Press. The bear’s eyes were ringed with black, its face was slightly indented, it had a mild hump to its back and long claws. Stirling said polar bears and grizzlies have been successfully paired in zoos and that their offspring are fertile, but there had been no documented case in the wild. [Source: Beth Duff-Brown, Associated Press, May 12, 2006]

Adam Popescu wrote in Washington Post: Textbooks say these two species aren’t supposed to inhabit the same environments. Polar bears are marine mammals; grizzlies are terrestrial. But as the Arctic warms, sea ice is shrinking and the tundra is expanding. And the bears’ disparate populations are meeting, mating and creating a new breed that’s capable of reproducing. Bears sharing both species’ DNA have been recorded several times over the past decade. So why are these two species linking up? It’s called flexible mate choice: The bears are mating with the best possible partners as opposed to not mating at all, and they’re mating because they share relatively close territories and the same branches of the same evolutionary tree. [Source: Adam Popescu, Washington Post, May 23, 2016]

Intraspecies mixing between the two happened thousands of years ago, thanks to the advance and retreat of glaciers, and of late, it has been boosted by climate change. Scientists say it’s also probably been assisted by policies that protect both bears from culling and hunting, affording further opportunities for mingling. The crossbreeds found in Alaska and Canada are not genetic anomalies. Scientists have found the mix in the islands off Southeast Alaska, where bears resemble grizzlies but contain polar bear DNA. That indicates decades of sporadic interbreeding, said Steven Amstrup, chief scientist at Polar Bears International. The polar-grizzly cocktail is also far from the only recent animal hybrid. The coywolf — a coyote-dog-wolf amalgamation — and a lynx-bobcat mix have been popping up along the northern Atlantic coast.

Prizzlies Favor Brown Bears At the Expense of Polar Bears

Adam Popescu wrote in Washington Post: Amstrup has studied bears in the Arctic since the 1970s and was instrumental in helping list the polar bear as a threatened species in 2008. He, like other experts, characterizes this “new” bear relationship as more beneficial to grizzlies than polar bears. That’s because there are more grizzlies than polar bears and because grizzly territory is expanding while polar bear territory is contracting. What that adds up to is a good chance grizzlies could essentially dilute the polar bear population until it doesn’t exist at all, they say. [Source: Adam Popescu, Washington Post, May 23, 2016]

Polar bears are getting the short end of the stick in this relationship, not “gaining any genetic diversity,” said Geoff York, who led research on polar bears at the World Wildlife Fund for almost a decade before joining Amstrup at PBI. Andrew Derocher, a professor of biological studies at the University of Alberta, has spent three decades studying bears throughout the Arctic. He, too, has a sobering view about where the hybridization is heading. “I hate to say it, but from a genetic perspective, it’s quite likely grizzly bears will eat polar bears up, genetically,” he told me. And he says the changes are already at play.

All hybrids that have been analyzed had grizzly fathers, because grizzly males roam to establish territory and come in contact with receptive female polar bears. Female grizzlies tend not to stray far from their home ranges, and male polar bears don’t usually creep into grizzly habitats. Polar bears need the ice — that’s where the seals and walruses they eat live. They don’t hibernate, and they don’t travel south of the tundra. Grizzlies, historically, rarely ventured north of the treeline. Permafrost is too cold for their liking, and they sink into the snow easily. (Polar bears have padded paws that act as snowshoes). Hunting is more challenging in the north, where prey is scarce. They’re not really swimmers.

“What we’re starting to see in the Canadian Arctic is three-fourth grizzlies,” Derocher said, referring to the offspring of 50-50 hybrids that then mated with grizzlies. “How do they act? Probably more like grizzly bears, living on land. As climate change continues, terrestrial habitat is going to increase, and the likelihood is the habitat for grizzlies, a terrestrial bear, is going to get better. That means a longer warming period and greater food potential.”

Derocher said it will not be long before we start seeing female grizzlies bump into male polar bears, further straining the polar bear’s genetic variation. “I suspect at the same time that that’s occurring, we’ll start to see polar bears on their way out. Some experts think that as the Arctic continues warming, it may be only a few decades, perhaps a century. There are about 20,000 to 25,000 polar bears in the Circumpolar Arctic, and “an order of magnitude higher for grizzlies in that area” and other brown bears, Derocher said. “It shouldn’t be a big surprise that grizzlies are moving north — everything is.”

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated May 2025