Is that a Brown Bear or Grizzly?

A male Brown Bear grazing sedges in Katmai National Park.

A male Brown Bear grazing sedges in Katmai National Park.

I have just returned from guiding a photography trip to the coast of Katmai National Park. It was spectacular, and you can look for some photos to appear here in the next day or two.

Katmai is packed with bears. SO many bears… Huge, lumbering, and brown, we watched them by the dozen (not joking) as they grazed like buffalo on the sedge meadows.

These bears are different, in a lot of ways, from those I encounter in the Brooks Range and the mountains of Alaska’s interior. First, these monsters of Katmai are so much bigger, twice the size. They are generally darker and less “grizzled”. But perhaps most obviously, they are far more comfortable around other bears, and humans.

A mile or two up from the mouth of the Swikshank River, there is a huge sedge meadow where we spent an evening watching and photographing. There were more than 20 bears in the meadow, including at least three females with cubs. In the Brooks Range, there is never such a congregation. Mountain bears of interior and northern Alaska have a personal space of hundreds of meters. They don’t like to get anywhere close to people or to other bears. Bears of Katmai have no such limitations. They will happily graze within yards of one another and have a similar outlook on humans.

So yeah, they are bigger, darker, and more tolerant. But at the level of their genetics, they aren’t so different.

A female Grizzly Bear wanders down the Kugrak River in Gates of Arctic National Park in Alaska's Brooks Range.

A female Grizzly Bear wanders down the Kugrak River in Gates of Arctic National Park in Alaska’s Brooks Range.

There are a bunch of recognized subspecies of Ursus arctos, the Brown Bear. In Alaska, there is the Grizzly Bear (Ursus arctos horribilis), the Kodiak Bear (Ursus arctos middendorffi), and the coastal Brown Bear of the Alaska Peninsula (Ursus arctos gyas). The caveat is that these (and a few others that are no longer widely recognized) were described based on the bears’ physical characteristics back in the late 1800s. Technology has since changed.

Current genetic tools have yielded some interesting information about Alaska’s bears. Turns out that size and other physical characteristics aside, they aren’t really so different from one another. (The one exception is the Kodiak Bear which, due to its isolation since the end of the last ice age, is unquestionably different from the rest of species’ populations.)

Now, let’s step back and talk for a moment about subspecies. A subspecies is a taxonomic category within a species. A full species, in general, does not, or cannot, interbreed with other species. Subspecies are not so restricted, and are completely compatible with other populations, but due to geographic isolation, usually don’t mix. Subspecies are genetically distinct, and therein lies the problem in the categorization Alaska’s bears.

Subspecies are genetically distinct, and therein lies the problem in the categorization Alaska’s bears.

Differences of both size and genetics in Alaska’s mainland bears are clinal. Meaning that the differences between populations is not sudden, but rather tapers. In the case of size and coloration, Ursus arctos becomes steadily darker and larger as we drop from the interior mountains to the coast. The genetics show the same: coastal bears are different, but not much, and consistently share genes with other populations.

From the recent genetic work on the species, it looks like the subspecies Ursus arctos gyas, the Alaska Peninsula brown bear (including Katmai), should be chucked out. It just doesn’t stand up to the necessary genetic and phenotypic tests.

A male Brown Bear in Katmai National Park. (This guy had just woken up from a nap).

A male Brown Bear in Katmai National Park. (This guy had just woken up from a nap).

If it’s not genetics, then why are the bears of Katmai so much bigger than interior bears? Well, it’s ecology. The coastal bears are living the good life. They have huge runs of protein and fat-rich salmon on which to feed. When the fish aren’t running there are mudflats full of shellfish and meadows growing an endless supply of sedges. Interior and northern bears, however, have to work for a living. They cover huge territories and are forced to be more predatory, eating caribou and moose calves, ground squirrels and bird nests. Berries in the fall, and roots in the spring round out their hard-won diet.

It’s easy to grow big when you have a lot of easily accessible food, and so the Katmai bears and those elsewhere along the coast of Alaska, get big indeed.

It’s easy to grow big when you have a lot of easily accessible food, and so the Katmai bears and those elsewhere along the coast of Alaska, get big indeed.

The abundance of food also results in behavior changes. There is no need to actively defend an abundant food source, so the bears of Katmai tolerate one another and humans in much closer quarters. In the Brooks Range? Not so much.

What all this means for us, is that the bears of Katmai are awesome. You can see them up close, watch their behavior, even make eye contact. And that, is thrilling.

So the answer to the leading question is that there really is no difference. If you want to call coastal bears Brown, and interior bears Grizzly, you won’t be wrong, but at the genetic level, they are all the same.

Information in this post comes primarily from these two articles:
Cronin, M. and M.D. MacNeil. 2012. Genetic Relationships of Extant Brown Bears (Ursus arctos) and Polar Bears (Ursus maritimus). Journal of Heredity 103(6): 873-881.
Paetkau, D., G.F. Shields, and C. Strobeck. 1998. Gene flow between insular, coastal and interior populations of brown bears in Alaska. Molecular Ecology. 7: 1283-1292.