Refuge Notebook: Drilling down into bear dentition — A (safe) look into the mouth of Alaska’s bears

A black bear. (Photo by Colin Canterbury/USFWS)

A black bear. (Photo by Colin Canterbury/USFWS)

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, teeth might not come to mind when you find yourself in bear country, but it is something worth considering.

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 the Ted Stevens Anchorage International Airport). But, when you see one, how much will you know about it? Its behavior? Its diet? Its teeth?

Alaska is fortunate 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.

The Kenai National Wildlife Refuge won’t disappoint — there’s a good chance you’ll see both black and brown bears.

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, or you can look to another remote refuge, the Izembek National Wildlife Refuge, located near the southern tip of the Alaska Peninsula.

It holds as many as nine coastal browns per square mile when the salmon are running. Areas of the refuge, such as the Joshua Green River Valley, provide prime bear habitat, its surrounding slopes offering denning habitat seen in few places in the world.

The Arctic National Wildlife Refuge is the only refuge in North America where you can see all three species!

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

Brown bears are usually noticeably larger than black bears. They can be nearly 3 meters long and weigh up to 1,500 pounds. Like black bears, brown bear colors can vary — from cream-colored to 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 and are sometimes called grizzly bears. Many believe the “grizzly” came along because of their grizzled look of silver-tipped fur.

To understand bears and their behavior, a great place to start is their teeth, 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). All three species share a similar dental formula of I3/3, C1/1, P4/4, and M2/3. A young bear will have the same number of teeth as a dog. However, as they grow older, their premolars can become reduced and sometimes absent as they are worn and lost as the bear matures.

Black and brown bears’ selection of foods requires a versatile set of teeth — they’re omnivores, meaning they eat a variety of things. The same bear seen feeding on the remaining carcass of a hunter-killed moose can have a meal of roots, berries, succulent vegetation and tubers. They feed on animals ranging in size from small rodents to large ungulates and everything in between.

Their opportunistic behavior means they might also top it off with some neighborhood garbage, bird seed from your feeder or lunch in your backpack. So, an excellent reminder that when living or visiting bear country, secure trash in a locked building, use bird feeders in the winter and keep backpacks close while fishing.

Black and brown bears have similar skull features. They have shorter maxilla and mandible bones resulting in generally shorter snouts. Large zygomatic arches and a more defined sagittal crest provide space and area for muscles such as the temporalis muscles — giving them their powerful bite.

These features result in large, stocky heads that appear round from a distance. Still, they can be differentiated by one another by the “dished” face of the brown bear.

Polar bears are the largest within the bear family, reaching weights of over 1,700 pounds. 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 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, lacking the large back hump found on brown bears. This linear body shape and large feet result in exceptionally great swimming. In addition, their feet have small “suction cups” on their soles for traction on slippery ice.

A polar bear’s skull appears “longer” than other bears, including their maxilla and mandibles. They also have a less defined sagittal crest. Together, these characteristics aid in their streamlined appearance. Their bite is still extremely powerful, but their choice of meat is generally softer than the diet of brown and black bears.

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

Their premolars and molars are sharper and have more resemblance to a serrated knife than the flat crushing molars and premolars of other bears. These jagged teeth 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.

So, when we think of bears in Alaska, the two on the Kenai and the third more distant, it is easy to see their more obvious difference and, looking deeper, that they are designed for the place they live.

Kristopher Pacheco with Katrina Liebich, Alaska External Affairs, U.S. Fish & Wildlife Service. Find out more about refuge events, recreation, and more at kenai.fws.gov or Facebook: https://www.facebook.com/kenainationalwildliferefuge. To find more Refuge Notebook Articles go to https://www.fws.gov/kenai-refuge-notebook

A brown bear. (Photo by Tim Bowman/USFWS)

A brown bear. (Photo by Tim Bowman/USFWS)

A polar bear. (Photo by Tim Bowman/USFWS)

A polar bear. (Photo by Tim Bowman/USFWS)

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