Yellowstone Grizzly Population at Risk of Decline

Sept 2013: Researchers believe there are fewer grizzlies in Yellowstone than previously estimated. Are there enough for the bears to be taken off the endangered species list?
Author:
Publish date:
yellowstone-grizzly-bear-population

Photo by USFWS Endangered Species

September 2013: Yellowstone’s grizzly bear population is not as high as previously reported. That’s the hypothesis of a new study by researchers at the University of Colorado-Boulder and the University of California-Berkeley, which asserts that the park currently has 600 grizzlies, far fewer than the previously estimated 718 bears.

Grizzly counting practices involve heavy statistics in which biologists collect observations over the course of a year and then extrapolate a total. The tallies are important because totals determine whether or not the animal remains protected under the Endangered Species Act. The U.S. Fish and Wildlife Service plans to hold a vote in 2014 over whether or not to delist grizzlies. If the species is taken off of the list, then states become responsible for their protection. The Denver Post reports that “Wyoming, Montana and Idaho are eager to take over grizzly management and perhaps set hunting seasons, much as they have for gray wolves, which were returned to state control in 2011.”

However arguments that grizzlies must remain on the endangered species list largely surround the decline of critical food sources like cutthroat trout that have been overrun by the invasive lake trout species.

"The Yellowstone grizzly is at greater risk of decline," Dave Mattson, a wildlife biologist who worked on the interagency grizzly bear team from 1974 to 1993, told the Post, "because we know less than we thought we did about population trends and the major deterioration of habitat and food sources."

Bears looking for high-calorie meal replacements and additions to pine nuts and trout often munch on army cutworm moths, which are found on open, rocky slopes. So because the bears spend more time out in the open dining on moths, the CU researchers guess that grizzlies have been easier to count, and more than likely, to overcount, than before when the bears spent more time in the forest looking for nuts and fish. Plus, the number of aerial count flights has tripled since 1995.

“If you fish one hour a week," Daniel Doak, one of the study’s authors, told the Post, "you get a rough idea of how many fish are in the pond." However, doubling the time spent fishing makes it more likely to catch something, but it doesn’t affect how many fish are in the pond.

So are there enough grizzlies for the bears to be taken off the endangered species list? It’s hard to tell. But Gary Frazer, Fish and Wildlife's assistant director for endangered species, makes a case that the bears should stay protected.

"The Yellowstone grizzly population (may not be) just stabilizing but declining, which would make a delisting decision even more difficult to defend," he told the Post.

Related

yellowstone-grizzly-bear-attack-010589097

Yellowstone Park May Delist Grizzlies

New research indicates that the grizzly bear has a more diverse diet than previously thought - including pine nuts, elk, bison, berries, trout, and insects - and that food sources available in Yellowstone National Park are sustainable for the bear population.

Grizzly bear in Yellowstone. Photo by Jake Davis.

Grizzly bear deaths in Yellowstone

A recent study by the Interagency Grizzly Bear Study Team finds that 10 of the 16 grizzly bears that have died so far this summer in Yellowstone National Park have died of natural causes.

Grizzly Bear at Swan Lake Flats. Photo by NPS Jim Peaco

Should Grizzly Bears be Delisted?

April 17, 2008: There are all kinds of answers to the question of whether the grizzly in the lower 48 is doing well enough to no longer require protection.

yellowstone-grizzly-deaths-high

Yellowstone Grizzly Deaths Highest in Four Years

According to statistics from the United States Geological Survey (USGS), 2012 saw the highest number of grizzly bear deaths in the greater Yellowstone area in the past four years. Researchers recorded a total of 51 bear deaths this year, compared to 44 deaths in 2011, 50 deaths in 2010 and 31 in 2009.

blog-yellowstone-grizzly-den

Grizzlies leaving dens

According to the National Park, Yellowstone grizzly bears have begun emerging from their dens in the park.