Field Notes

Where have all the moose gone?

by adminFeb 19, 2011
A Moose Drinks From A Pond In Jackson Hole

Driving north from the town of Jackson toward Moran junction in winter used to be a sure fire way to see moose. It was not unusual to see dozens of them grazing on the sage flats around the airport and laying around in the Gros Ventre river bottom. Moose were everywhere! That was five years ago.

Today you can take that same drive and not see a single moose. Look a little harder and you might find one or two tucked away in the willows along the Gros Ventre river or in somebody’s yard but they are not nearly as abundant or visible as they used to be. The declining moose population is well documented, easily noticed and has been studied to exhaustion by both government biologists and graduate students. Despite the attention, there have been no clear answers and a lot of debate.

One theory suggests that the moose had overpopulated Jackson Hole and ate themselves out of house and home by reducing their preferred browse in the valley like bitterbrush and willow. The problem with this theory is that there hasn’t been a noticeable reduction in their preferred browse that would cause such a significant decline. Another possible scenario being considered was that a new disease was affecting the population and increasing mortality in the Jackson area. Despite a lot of effort to find the mystery disease, no such pathogen was found and the hunt for the cause continued.

Some suggest that wolves are to blame but they can’t be totally responsible since the moose population had already been dropping precipitously well before the first reintroduced wolf wandered back into the valley in the late 90’s. What could cause the sudden decline of a well established prey species in a county where 97% of the land is protected by the federal government? A better understanding of history and context might shed some light on the subject.

When Lewis and Clark came west in 1804 one of their missions was to document and catalog everything they found along the way. Though there were a couple mentions of the expedition seeing moose along the way, they didn’t see many and those they did see might have actually been mule deer. Though they didn’t come through Jackson Hole, their accounts of pre-settlement flora and fauna in the west help us understand how things have changed since whites began settling the area. One of the biggest changes was a dramatic reduction in predator populations like bears, mountain lions and wolves. Through trapping, hunting and poisoning white settlers successfully removed or reduced predators from the west in an attempt to ‘tame’ the wilderness. Grizzly populations were reduced to near extinction and wolves were completely exterminated from the Greater Yellowstone area.

About the Moose in Jackson Hole

Without predators, Jackson Hole, once marginal moose habitat, became a place where moose could thrive. Prior to 1912 there were few, if any Moose, in Jackson Hole. By the mid 1960’s there were around 250 moose living year-round in the valley and by 1993 the Jackson moose herd had reached it’s peak of an estimated 3000-4000 animals. This rapid success into a new habitat certainly changed the landscape but I doubt that this alone would lead to a 75% decline in valley moose in under two decades. It is likely that something else changed the game for moose in Jackson Hole.

That something weighs 350-600 lbs, runs up to 40 mph, shares the same habitat as moose and has been moving back into Jackson Hole since the early 1990’s. Grizzly Bears, once relegated to feeding on trash and handouts in Yellowstone, have made an amazing comeback since their near extinction from the Greater Yellowstone Ecosystem. After being protected from hunting in 1975 their population has soared and they have been spreading out in search of new territory and food sources. Though grizzlies will predate moose, especially the calves, the real problem for moose is just their presence. Grizzlies spend a lot of time in river bottoms and meadows in search of food and will graze on many of the same plants that moose rely on. This added stress pushes moose to the margins of their habitat and decreases the time they can spend feeding in a given area. Decreased caloric intake through the summer and fall leads moose into winter in poor shape and decreases their chances of survival and reproduction.

I believe that the moose herd had probably overpopulated the valley around 1992 which, with the help of steadily increased hunting quotas, lead to their population to begin a decline. At the same time, Grizzlies began to move back into the valley and created a new stress that displaced them from some of their prime summer range. Finally, wolves returned to Jackson Hole adding a critical nail to the coffin of moose ever recovering to anywhere near pre-predator numbers.

In the last few years the winter distribution of moose in the valley has changed significantly concurrent with a dramatic increase in wolf activity. According to Teton National Park there are now over 60 wolves in 5 packs whose territory extends into Jackson Hole. As a wildlife photographer and guide I have noticed the change in moose numbers and distribution and the increase in wolf sightings on our safaris. Like the grizzly bear, the wolves aren’t necessarily killing a lot of adult animals. Instead they will opportunistically kill calves and through their presence add another stress that impedes feeding and rest; both critical for moose to survive the harsh Wyoming winters.

There is no doubt that predators are probably the main factor in the decline of the Jackson moose herd. Though depredation is certainly a part of the puzzle, I believe that stress and the interruption of grazing is a larger factor based on my time observing moose, grizzlies and wolves.

One positive change for the moose of Jackson Hole is people and the protection from predators that we provide. If you want to see moose you will find them in the neighborhoods on the west bank of the Snake river, the backyards in Wilson and even laying around in the town of Jackson. Moose have learned that people aren’t a threat and that grizzlies and wolves tend to avoid contact with humans. One study even showed cow moose in Grand Teton National Park moving closer to roads to birth and raise their calves once grizzlies moved into their area. The predator prey relationship is complex, ever changing and certainly includes us. Though we try to act like an observer there is no doubt that we are a participant.