re being given a path before (under Endangered Species Act protections), will not have that any longer,” he predicts.
The Long Road to Recovery
There were once an estimated 50,000 grizzly bears in the western half of the contiguous United States. As European settlements spread across the West, most of the animals were shot, trapped or poisoned — the victims of the same kind of hostility that confronted wolves, mountain lions and other large carnivores. Grizzlies in the West had been pushed back into a few pockets in the Northern Rockies that constitute less than 4 percent of their former range.
By the time the isolated Yellowstone grizzly population was protected under the Endangered Species Act in 1975, there were as few as 136 bears. The Yellowstone population had been sharply reduced after open-pit garbage dumps that were favorite grizzly feedings grounds were closed in Yellowstone. After they were protected the Yellowstone grizzly population steadily expanded throughout the 1980s and 90s. Their numbers leveled off after the turn of the century.
No one knows for sure how many grizzlies are roaming Yellowstone and Grand Teton national parks and the adjacent national forests and wilderness areas and beyond that make up the Demographic Monitoring Area. The best that can be done is to make reasonable estimates.
The estimated total population of grizzlies within the Demographic Monitoring Area is based on a complex model called the Chao2 estimator which extrapolates the overall population from the number of female bears with newborn cubs counted each year.
Van Manen says the Chao2 model underestimates the number of grizzlies, particularly as the population increases. “When we say there are around 700 bears in the ecosystem, that is severely underestimated,” he says. “The bias is as much as 40 to 50 percent.”
The U.S. Fish and Wildlife Service has been trying for years to declare Yellowstone’s famed bears a conservation victory by removing them from the endangered species list. But that effort has been the source of long-simmering controversy and litigation. The agency delisted the bears in 2007, but environmentalists sued and federal court decisions put the bears back on the endangered list in 2009.
At that time, the court ruled that the Fish and Wildlife Service failed to evaluate the impact of the collapse of whitebark pine forests throughout the Yellowstone region. The pine seeds serve as a major food source for some grizzlies. The agency spent the next few years studying the impact.
In 2013, the Interagency Grizzly Bear Study Team found no relationship in the decline of whitebark pine and the overall health of grizzly bears, which are famous for being opportunistic omnivores and very flexible in their diet. A second study in 2015 came to similar conclusions.
“We are not seeing for either males or females that the percent of body fat is declining, which would have to happen for these changes in food resources to start taking a toll on the population,” van Manen, one of the authors of each study, says in an interview.
Now, one of the key points of contention is whether the population in and around Yellowstone can be considered recovered in isolation from several other populations in the lower 48 that remain very much a work in progress.
The American Society of Mammalogists and the Society for Conservation Biology sent a joint letter in May 2016 opposing the Fish and Wildlife Service’s then-proposed piecemeal strategy of removing the Yellowstone grizzlies from endangered Species Act protections before the entire grizzly population in the lower 48 states is recovered.
“In our professional judgment,” the letter stated, “both the best available science regarding carnivore recovery and the plain language of the ESA obligate USFWS to manage the metapopulation of grizzlies in the lower 48 states, not just each population individually.”
A metapopulation is a group of populations of the same species that are separated by space. These spatially separated populations interact with individual members moving from one population to an