Where art thou, moose?

By WHITNEY ROYSTER
Star-Tribune environmental reporter

JACKSON -- Here's a tip: When tracking moose with Scott Becker, wear pants.

Wear sneakers or hiking boots, of course, but for Pete's sake, don't try to impress Becker by wearing a skirt. Your calves, shins and knees will look like someone's taken at you with a switch.

Following Becker through fields of sage and bitter brush with a backdrop of the Tetons, it's hard not to envy his work. He held an H-shaped antenna above his head and picked up faint blips of a signal.

"She's in those trees," he said, pointing down a meandering creek on the prairie fronting Grand Teton National Park. It was the first time he hadn't referred to the moose as "my gal."

Becker, a University of Wyoming graduate student, is the go-to man these days for moose studies.

Becker is in the second of a three-year study to help identify the cause of moose decline in northwest Wyoming. Since the early 1990s, moose numbers have been dwindling, and Wyoming Game and Fish Department officials have been scratching their heads. So, the department has created a moose study team, and has hired Becker and others to study the animals.

Not all of Wyoming's moose population is struggling. For example, moose have recently expanded into the mountain ranges of south-central Wyoming from an introduced herd in northern Colorado, and those animals are doing well, Game and Fish officials say.

But Wyoming's largest moose populations are in the west and northwest, and the latter are struggling. The Jackson moose herd, for example, has dropped from an estimated 4,000 animals in 1995 to under 3,000 today.

Statewide, Game and Fish estimates there are about 11,066 moose. The agency has a statewide population objective of 14,530 moose.

No clear answer

Becker's study in part takes off where a previous study, headed by Joel Berger and the Wildlife Conservation Society, left off. Berger concentrated on the effects of predation on moose; Becker's study seeks to explain what habitat moose are using most. Is that habitat dwindling and affecting moose populations?

Becker is also looking at survival rates of adults, and when he can, calves, to see what segment of the population is limiting overall moose numbers.

It's a tricky business. Survival rates for adults Becker has been watching are normal -- in the mid to high 80 percent range. Pregnancy rates are normal, too. But calf survival rates are low.

The cause? That's unclear. Becker's study is not concentrating on calf survival rates -- he's not collaring young moose as he does adults -- so gleaning that information is a challenge. By the time researchers get to a calf carcass, the cause of death is nearly impossible to determine.

"It's possible females are in poor enough condition, they give birth to calves of poor health so they don't survive outside of the womb," Becker said. "The only known mortality we did have last year was a calf got hung up on a fence."

It's possible the research has something to do with it. Of 20 cows fitted with GPS collars last year, only three were observed with calves later, according to a report by Becker. Of "non-handled" cows, about 75 percent had calves.

But for the most part, researchers agree that moose are suffering because of dwindling habitat.

Predation

One thing Becker and Berger seem to agree on is that predators are not having a big impact on moose numbers.

In Berger's decade-long study, research pointed to malnourishment as the primary cause (60 percent) of adult female moose deaths. Predation by bears was the second-leading cause (14 percent), followed by hunting (10 percent). Predation by wolves was less than 2 percent. Roadkill amounted to 8 percent of deaths.

Becker agrees that predation is not having a big impact, though he says the point of his study is to look at survival rates, not mortality rates.

"It doesn't appear predators are having much of an impact on adult survival," Becker said.

The Game and Fish Department agrees.

Reg Rothwell, supervisor of biological services, said the decline in moose numbers appears to be habitat-related.

"Anything that has to do with the environment, it's seldom one thing that's the cause," Rothwell said. "A lot of times, it's a lot of history building up, not necessarily something new."

Years of drought, Rothwell said, could be catching up to northwestern moose populations. Moose here have the lowest numbers of cows having twins "on the planet," Rothwell said, suggesting an overall health problem.

When driving from Pinedale to Jackson, Rothwell said, people can see drainages with extensive willows. Some of those willows are hammered by moose. That could mean moose are over-utilizing the willow species they like and are more nutritious to them, leaving less-nutritious and desirable willow.

"If you take that problem and compact it by drought, it may be some kind of compounding thing," Rothwell said.

Bob Wharff, executive director for the hunters group Sportsmen for Fish and Wildlife, said moose population declines cannot be laid "solely at the feet of predators."

But, he said, there has not been a comprehensive study on the physiological effects of predation -- the stress the predators cause in moose. That stress, he said, can lead to lower pregnancy rates, low calf survival and even animals leaving an area to get away from predators, causing population redistribution.

"It only goes to reason if you're something that can be killed by a lot of different predators, the more those predators increase, it's going to add to the stress you're going to have," Wharff said.

But moose populations in the Sublette herd are also declining -- an area generally without wolves and grizzly bears.

Both Berger and Becker said they have not seen any indication of predators chasing moose in their studies.

"Honestly, from what I've seen this winter, I don't think it's too much of an issue," Becker said. "It may happen in some cases, but in all the winter up here I was watching these moose, I rarely saw a wolf actually chasing them around. There was only one cow I saw with wolf tracks around, and I know she was harassed. It's another theory out there that we're going to try to find what the cause (is) for the decline."

In the field

Becker said his study expands on Berger's, in part because of a bigger budget -- about $250,000 over three years. Berger collared 18 animals; Becker has 62. Berger tracked the animals on foot; Becker has the help of helicopters.

Becker's study, funded in part by the Game and Fish Department, the Wyoming Department of Transportation, University of Wyoming and Wyoming Animal Damage Management Board, also seeks information on highway crossings. He also intends to plug population numbers into a computer model to see if that helps determine what population segment is limiting population growth.

Although some have taken the Game and Fish Department to task for being anti-predator, Becker flatly denies his study's role is to implicate predators in moose declines.

"This is a survival study; the cause of mortality is secondary," Becker said. "If adult survival is within normal ranges, there's no need to look at that."

But there is a need to track moose, which was Becker's objective on a recent day at the foot of Teton National Park.

The cow moose's collar near the Tetons continued to blip off the antenna. Becker wanted to see if his "gal" had a calf.

The arrowleaf balsam roots were opening and turning their heads to the sun. The cow apparently was turning her head, too, making radio-tracking more difficult. At every turn, Becker insisted she was "just in the next bunch of trees."

A swift and high Ditch Creek prevented further travel. So today, the cow moose will remain unstudied, illustrating again the complexities of understand moose populations around the Tetons.

Posted on Sunday, July 02, 2006