Drilling Down into Bear Dentition

A (safe) look into the mouths of Alaska’s bears

What comes to mind when you think of bears? Smokey? Losing the playoffs? What about teeth? Whether you’re hunting, fishing, hiking, or just outside taking out the trash, it’s hard not to have teeth come to mind when you find yourself in bear country.

Kodiak brown bear looking directly at the camera
Kodiak National Wildlife Refuge is home to some of the largest brown bears in North America. Many taxonomists consider “Kodiaks” to be a sub-species. 📷 Lisa Hupp/USFWS

If you’re a lifetime resident or just visiting Alaska, eventually you’ll encounter a bear (even if that’s only the large brown bear mounted in Anchorage International Airport). When you do see one, how much will you know about it? Its behavior? Its diet? Its teeth?

Bears of Alaska’s National Wildlife Refuges

Alaska is lucky enough to have three species of bear within its borders: black, brown, and polar. If you’re visiting one of the U.S. Fish and Wildlife Service’s 16 national wildlife refuges in Alaska, you’ll be able to see all three (in fact, Arctic National Wildlife Refuge is the only refuge in North America where you can see all three).

close up of a polar bear facing the camera
Polar bear. 📷 Lisa Hupp/USFWS

If you’re looking for a refuge on Alaska’s road system, Kenai National Wildlife Refuge might be for you; it won’t disappoint — there’s a good chance you’ll see both black and brown bears.

close up of a black bear
A black bear in Kenai National Wildlife Refuge 📷 Colin Canterbury/USFWS

If you’re looking for quantity, the brown bears of Alaska Peninsula National Wildlife Refuge appear in some of the highest densities known in the entire world.

brown bear walking along an edge of a wetland
A brown bear in Alaska Peninsula National Wild Refuge. 📷 Bob Dreezen

Your search for big, abundant bears could take you to another remote refuge; Izembek National Wildlife Refuge located near the southern tip of the Alaska Peninsula. As many as nine coastal browns per square mile can be seen when the salmon are running. Areas of the refuge such as the Joshua Green River Valley, provide prime bear habitat with world-renowned brown denning habitat on its surrounding slopes.

Whichever refuge in Alaska you visit, it’s pretty safe to assume you are in bear country.

a black bear in the bushes
Black bear in Selawik National Wildlife Refuge. 📷 Steve Hildebrand/USFWS
close up of a brown bear skull
A 12-year-old coastal brown bear skull (a boar) from Izembek National Wildlife Refuge 📷 Katrina Liebich/USFWS

Bear Teeth

To understand bears and their behavior, a great place to start is their teeth, and more specifically, dental formulas. Dental formulas are commonly used throughout the study of animals and can be a way to identify a type of animal. There are four types of teeth: incisors (I), canines (C), premolars (P), and molars (M). Here is a human dental formula: I2/2, C1/1, P2/2, M3/3. This means on one side, both the top and bottom, there are 2 incisors, 1 canine, 2 premolars, and 3 molars. Multiply this formula by 2 and you have a total of 32 teeth in the human mouth. Don’t take our word on it, go take a look in a mirror!

Black Bears (Ursus americanus)

Don’t let their colors fool you — black bears are not always black. Their pelage can be observed in a large variety of colors, from light brown cinnamon, to dark black and everywhere in-between. They’re generally smaller in size than the other two species, but can be as large as 700+ pounds.

black bear at a bird feeder
Black bear. 📷 Tim Bowman/USFWS

Black bears’ selection of foods requires a versatile set of teeth—they’re omnivores, meaning they eat a variety of things. The same black bear seen eating a hunted deer can be seen having a meal of roots and berries, topped off with some neighborhood human garbage or bird seed from your feeder. Many might be considered opportunistic eaters, taking advantage of just about anything in the area.

A black bear has a dental formula of I3/3, C1/1, P4/4,M2/3. A young black bear will have the same number of teeth as a dog. As they grow older their premolars become reduced or possibly absent as they are worn and lost as the bear matures:

close up of black bear skull and front teeth
A younger black bear from the Kenai Peninsula 📷 Katrina Liebich/USFWS
black bear skull from the front
An old (27-year-old sow) black bear from Prince William Sound 📷 Katrina Liebich/USFWS
Lower jaw of a black bear
Lower jaw of 27-ear-old black bear sow from Prince William Sound, Alaska. Note premolars reduced and missing. 📷 Katrina Liebich/USFWS

Brown Bear (Ursus arctos)

Brown Bears are usually noticeably larger than black bears. They can be nearly 3 meters in length and weigh up to 1,500 pounds. Like black bears, brown bear colors can vary — from cream colored, dark brown, to almost black. One noticeable feature is the hump on their backs just above the shoulders. Coastal brown bears are known to grow to larger sizes than their interior relatives.

Two sow brown bear with cubs negotiating fishing space in Kodiak National Wildlife Refuge. 📸 Lisa Hupp/USFWS

Interior brown bears are sometimes call Grizzly Bears. Grizzlies are their own subspecies (Ursus horribilis). Besides size, many believe the temperament of grizzlies to be different from coastal brown bears. Grizzlies have been known to react to human encounters at shorter distances; possibly having something to do with their subspecies specific epithet horriblis. Many believe the “grizzly” came along because of their grizzled look of silver-tipped fur.

Brown bears’ diets vary. 📷 Tim Bowman and Lisa Hupp/USFWS

A brown bear’s diet is similar to that of a black bear. Their diets can vary and include berries, succulent vegetation, and tubers. They can also feed on other animals ranging in size from small rodents to moose and everything in between.

front end of a brown bear skull
A 12-year-old coastal brown bear boar from Izembek National Wildlife Refuge. 📷 Katrina Liebich/USFWS

Black and brown bears have similar skull features. If you’re looking into using a firearm for bear protection in bear country, you’ve probably come across information on high penetration ammunition. This is due to penetrating their tough bone to include their skulls. Brown and black bears have shorter maxillas and mandible bones resulting in generally shorter snouts that provide powerful bites. Large zygomatic arches and a more defined sagittal crest provide space and area for muscles such as the temporalis muscles—this gives them their powerful bite. These features result in large, stocky heads that appear round from a distance.

Polar Bear (Ursus maritimus)

Polar Bear are the largest within the bear family, reaching weights of over 1700 lbs. They’re also considered a marine mammal due to their dependence on the marine environment including sea ice. Their white to yellowish pelage does more than just camouflage a bear against snow and ice—it’s made up of water repellent guard hairs and dense underfur. Black skin underneath helps absorb warmth. Polar bears differ from other bears in many ways besides their specialized coats; their body shapes are streamlined and lack the large back hump found on many brown bears. This linier body shape and large feet result in exceptionally great swimming. Their feet have small “suction cups” on their soles for traction on slippery ice.

polar bear standing on sea ice with water in the background
A polar bear on sea ice. 📷 Tim Bowman/USFWS

All these specialized features make polar bears extremely effective hunters. Given their marine nature it’s not hard to guess that a polar bear’s diet is solely carnivorous and consists of marine mammals. Their dental formula may be the same as other bears, but taking a closer look at their teeth can provide some proof that these large mammals are built to hunt and eat solely meat.

front view of a polar bear skull
📷 Katrina Liebich/USFWS

A polar bear’s skull appears “longer” than other bears. Their maxilla and mandibles appear longer and a less defined sagittal crest aids in their streamlined appearance. Their bite is still extremely powerful, but their choice of meat is generally softer than that of the diet of brown bear and black bear.

side view of polar bear skull
Polar bear skull. 📷 Katrina Liebich/USFWS

Taking a look at a polar bear’s premolars and molars in comparison to other types of Alaskan bears, you’ll notice they are sharper and might have more resemblance to a serrated knife than the flat crushing molars and premolars of other bears. These jagged molars and premolars are more effective at processing through meat of a hunted or scavenged kill. It’s like taking a quality steak knife to a steakhouse rather than a dull butter knife.

Bon appetit!

Compiled by Kristopher Pacheco with Katrina Liebich, Alaska External Affairs, U.S. Fish & Wildlife Service.

In Alaska we are shared stewards of world renowned natural resources and our nation’s last true wild places. Our hope is that each generation has the opportunity to live with, live from, discover and enjoy the wildness of this awe-inspiring land and the people who love and depend on it.

Follow us: Facebook Twitter fws.gov/alaska/

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The U.S. Fish and Wildlife Service is working with others to conserve, protect, and enhance fish, wildlife, plants, and their habitats for the continuing benefit of the American people.

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