In the second of our series on the scientists who inform WOC’s conservation strategies, WOC talks to wildlife biologist Joel Berger about his work in the Greater Yellowstone Ecosystem. Based in Driggs, Idaho, Berger has traveled the world to study its large mammals. His research in Wyoming has helped WOC frame its position on issues ranging from oil and gas development in the Upper Green River Valley to migration routes from Yellowstone south.

Joel Berger grew up in Los Angeles and hated it.

From an early age he longed for places where there were no crowds, no cars, no houses. The closest escape for him in those days was the Mojave Desert where he first started watching animals. Today is he still watching animals. In fact, he is willing to crawl through sagebrush, wallow in the willows, dress up in a moose costume, roast under the baking desert sun, freeze in the Arctic, and fly to distant parts of the globe to watch them.

Wolves, griz and moose
Berger is a world-renowned wildlife biologist who has spent the last 10 years focused primarily on moose in the Greater Yellowstone Ecosystem. His findings, particularly those regarding the effects of predators on moose, are somewhat surprising.

"Two percent of the deaths of adult moose in the study area can be attributed to wolf predation," Berger says. "Another 15 percent were due to grizzly bears, but the vast majority—60 percent—of the deaths were due to starvation.

"People may hear this and say, ‘Is he some kind of animal rightist? Is he trying to make predators look good?’ Absolutely not. This is the science talking." Berger concludes.

Berger, who works for the Wildlife Conservation Society, says his work in Wyoming actually has its roots in a study he conducted in the Arctic. This study focused on two different populations of caribou: one in Alaska that coexisted with predators, the other in northern Greenland and Norway that did not. He found that the caribou in Greenland and Norway—the "naïve" caribou—did not respond to signs or smells associated with predators. Unlike their cousins in Alaska, which became alert and tense when they smelled grizzly bear scat or heard a wolf howl, the Scandinavian caribou continued to graze undisturbed when exposed to these stimuli. Fear of predators appeared to be a learned behavior.

The caribou study had interesting parallels with the situation in Wyoming where moose and elk had lived in the absence of a significant predator threat since the 1930s when bears and wolves were largely wiped out by humans. What was intriguing about the scenario in Wyoming, when Berger began to look into it, was that the predators were coming back. Grizzly bear numbers were on the rise and wolves had been reintroduced. The big question he wanted to answer was: How would moose respond?

As with the Scandinavian caribou, Berger found that naïve moose in Wyoming did not react to scents or sounds normally associated with wolves or bears. That’s where the moose costume came in. Berger dressed up as a moose in order to get close enough to the animals to plant bear feces in their midst. Unfortunately, in Berger’s opinion, the moose costume got more press attention than the science it was being used to advance. He was even asked to appear on the David Letterman show in his costume.

"Dressing up like a moose has been overblown by the media," Berger complains. "It was one way to get close to non-habituated moose, but the media decided it was a cutesy gimmick… . We’ve backed off using it because it detracts from the seriousness of our work. "We ended up turning down Letterman because they wouldn’t guarantee we got 60 seconds to establish our scientific credibility," he adds.

Gimmick or not, the experiment with the moose costume helped prove that the naïve moose did not know to be afraid of predator signs. Other field observations confirmed this finding.

"When moose first came in contact with wolves they did not respond. The wolves came within five yards of them, and the moose just stood there like the wolves were big coyotes," Berger says. "Wolves could take down a 200-pound, six-month old calf without the calf’s mother doing anything. But in a year, the moose had become savvy. It didn’t take long for them to recognize the danger of wolves."

Starvation versus predation
But if predators aren’t the reason the moose population is in decline in the Greater Yellowstone Ecosystem, what is? There is no doubt numbers are down, as are pregnancy rates. By analyzing progesterone levels in cow moose droppings, Berger has been able to determine that only 75 percent of adult female moose in the Yellowstone area are pregnant compared to 90 percent in 1966. He doesn’t think the reason for this drop is pressure from predation.

"Populations densities in the area have been really high in the past," Berger says. "Moose didn’t occur here in large numbers until bears and wolves were killed off in the late 1930s. Once the predators were gone, the moose population boomed, and they hammered the riparian vegetation, particularly in the park where there is no hunting."

"Because moose have expanded so greatly and they are now at such high densities, it is possible that they are over-eating their food sources," Berger says.

This determination seems to be reinforced by the differences Berger has observed between moose habitat in Grand Teton National Park, where there is no hunting, and in the surrounding area, where there is. Streamside willows in the park have been stripped bare while outside it they are healthier and more abundant. Neotropical birds, like warblers, seem to have abandoned the park but they can still be found along streams outside where there are fewer moose.

"We are pushing the envelope here and suggesting that knowing pregnancy rates can tell us whether populations [of moose] are at or above the food ceiling of their ecosystem," Berger says.

"Having more predators or hunters in the situation may actually help," he adds. "Hunters have generally been good until recently [because they control population numbers]. But that’s changing. Which brings me to my last point. No one wants to hear this one, but global warming also appears to be having an effect [on moose numbers]."

Berger has found evidence indicating that warmer temperatures are putting additional stress on cold-adapted animals like moose. These animals are not doing well in the southern limits of their distributions, and while he concedes that drought is part of the equation, he thinks that we may be seeing a northern migration of cold-adapted animals as the world warms.

More than moose
Focusing solely on Berger’s work with moose provides insight into only one aspect of the man’s varied and colorful career, however. He studied bighorn sheep for his doctorate from the University of Colorado, then he went to the Badlands of South Dakota to look into how horn size affects bison reproductive success. From there, his work took him to Africa where he conducted research on the possibility of dehorning black rhinos to protect them from poaching. He’s watched moose interact with tigers in Siberia and followed caribou throughout the Arctic. For his next project, he’s leaning toward trying to get white-tailed jack rabbits reintroduced into Grand Teton National Park where they have been extirpated.

And in Wyoming, Berger has also been examining the migration paths of pronghorn from Yellowstone National Park down into the Upper Green River Valley. His work, in conjunction with that of his wife, Kim Berger, who is finishing up her doctorate in wildlife biology with a focus on pronghorn, has been instrumental in drawing attention to the importance of these ancient migration paths.

Using radio collars and GPS, the Bergers have tried to define these pathways in order to protect them from encroaching development. Pronghorn remain the lone, long-distance migratory species in the Western Hemisphere, excepting in the Arctic, where caribou continue to make annual pilgrimages to escape winter. Pronghorn move southward from Yellowstone into the sagebrush steppe of the Upper Green River Valley and back each fall and spring—a distance of more than 300 miles roundtrip. They have done this for at least the last 5,800 years. Their path takes them through three bottlenecks, the most infamous of these being Trapper’s Point. Less than a mile wide, Trapper’s Point is both a major oil and gas development area and the site of two subdivisions. If the pronghorns’ route is severed—particularly at one of the bottlenecks where the animals have few other options—Berger believes pronghorn will go extinct in Grand Teton National Park.

"Why should we care? Because this is the second longest migration in the Western Hemisphere exceeded only by caribou in the Arctic. Why don’t we take pride in this? Pronghorn are an icon of Wyoming, why aren’t we celebrating them?" Berger asks.

"We can’t turn back the clock. People born today in Los Angeles, in New York, in Casper are never going to see millions of bison migrating across the plains, but we can still show our kids long-distance migrations in western Wyoming.

"This is a chance for Americans to show the world that we care about conservation. That we can do things right," Berger concludes.

Doing things right for the Bergers and other conservationists, including WOC, would be the creation of some kind of national migration corridor that would keep the pronghorns’ path open in perpetuity. Berger believes that this may be a battle conservationists can win.