Washington State University

Ask Dr. Universe

Trouble in Bear Land

January 6th, 2012

Dear Dr. Universe,
How many grizzly bears are left in the world?
Anthony Alvarez
New York

Winnie the grizzly bear at WSU.

Winnie the grizzly bear at WSU.

As you can imagine, counting grizzly bears is pretty hard, and estimates vary a lot. Grizzlies might be big, but they don’t care to be seen. So I checked with Rob Wielgus, a wildlife biologist here at Washington State University who studies large predators.

He estimates that in the lower United States, there are probably fewer than 700-900 grizzlies. That, he says, is probably less than 1 percent of their population before the U.S. was settled by non-natives. There were about 100,000 bears in the lower U.S. in the 1850s, but they have disappeared from 99% of their former range. Professor Wielgus adds that there are probably 700-800 grizzlies in Alberta. British Columbia might have as many as 10,000-13,000, though he says that is a government figure and could be way too high.

There MIGHT be 35,000 grizzlies in Alaska and 6,500 in the Yukon, but Professor Wielgus says these guesstimates could be way off.

But you asked about the world population. Grizzlies, also called “brown bears,” live in Asia and Europe. In fact, most of the world’s brown bears live in the conifer forests of the former Soviet Union. The total worldwide population? Perhaps 125,000-150,000, but no one really knows. Most biologists believe that grizzlies are declining worldwide.

So even 150,000 isn’t very many if present trends continue.

In spite of grizzlies being “threatened” in the lower U.S. and “vulnerable” in Canada, they are still hunted, which causes some unexpected problems, says Professor Wielgus.

One common justification for hunting grizzlies is that killing large males makes more room and more food for more cubs. According to this argument, “removing” adult males increases the number of cubs produced by females and cub survival rate. More available food means more cubs.

Professor Wielgus believes the opposite happens.

Grizzly cubs stay with their mother for as many as three to four years. The number of female grizzlies in an area depends on how much food there is. The number of male grizzlies depends on how many female grizzlies there are. If the food is plentiful, a grizzly male’s home range will be about a thousand square kilometers.

A male grizzly does not appreciate male company. He wants these females for himself, to raise HIS cubs. So if another male tries to invade his turf, he’ll kill him or chase him off.

But let’s say some trophy hunter wants a bear rug for his den, so he shoots Mr. Griz. What happens next, says Professor Wielgus, is that all these younger male grizzlies come to the funeral and start fighting for the territory.

Even if one of them chases off his competitors, that’s not good enough. HE wants the females to himself, to start producing HIS offspring. But if females are nursing cubs, they cannot get pregnant.

This is a major problem to a young male who wants his own cubs. So he starts killing the cubs to make room for his own and to get the female to breed. Grizzlies can be pretty intense.

Of course the female grizzly is not going to hang around and have her cubs killed. She might take them out of the area, maybe to where there’s less bear food and solitude, where males are unlikely to go. Maybe, in other words, to real crummy areas where food is scarce. Or she moves into human territory and starts digging through garbage cans.

So let’s sum up. What happens when somebody shoots a large male? The grizzly world gets very upset. Lots of young males, who are often troublemakers, move into the territory. Mrs. Griz might go to town to escape the new guys.

Also, more males means more demand for food. Of course, humans get all upset when the young males start showing up in their back yards and eating their sheep. So somebody decides, hey, we’ll solve this problem. We’ll shoot that male and everything will be fine.

WRONG, says Professor Wielgus. It just starts the problem all over again! The griz population gets bigger because of more young males! And more ornery.

But what happens eventually, says Professor Wielgus, is the population just can’t stand the upset. Because of the influx of males, the population goes up, up, up. Then all of a sudden, all of the offspring have been killed, there are no more females, and without females, it’s good-bye grizzlies.

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