Ever wonder why in Yellowstone and Jackson Hole that the only animals you typically see during most of the day in the summer are bison and pronghorn? This is due to the these animals ability to thermoregulate. Thermoregulation is basicaly your ability to control your body temerpature. Sure, this is one of the distinct characteristics that all mammals have in contrast to, say, reptiles (except for the leatherback sea turtle). Though mammals can control their body temperatures, some are more adapted at surviving the head and direct effect of the sun than others. Much of this has to do with animals ability to cool their brains, and how long that such animals have been exposed to such environments throughout their evolutionary history.
Cervids, or the deer family, are one of those groups of animals that cannot tolerate high temperatures and are what we call crepuscular in nature. Meaning, they are active at dusk and dawn primarily for this reason. This is why in Yellowstone and Jackson hole elk, moose, dear are few and far between except for at dawn and dusk. Its the same thing with bears as well. Many animals respond to the warming temperatures by either hiding on day beds (moose) or otherwise moving up in elevation to where they can follow the Spring up above tree line (grizzly).
As I began to plan for this years trip to Jackson Hole for the fall rut, temperature was therefore heavy on my mind. An unseasonably warm spell had settled over the region and temps had climbed as high as 80 the day before I arrived in town. Speaking with other photographers that were in Yellowstone, my fears had been confirmed that wildlife was few and far between. Luckily however, my first full day in the valley was forcasted to see a major change in weather patterns as temps were to begin dropping.
When it comes to Jackson Hole and Grand Tetons National Park, the first thing I think of in terms of wildlife photography is moose. Its the name of one of the towns in the valley and even the symbol of this national park. Thus, when I come to Jackson for photography, moose are usually first on my list to search for. Unfortunately though, the Jackson Hole population has begun to crash over the last 10 years with a population size diminishing from nearly 3,000 individuals to 970.
A lot of speculation has circulated in regards to what has caused this sort of rapid and alarming decline and much of it falls on to the shoulders of a rising population of predators in the valley. Wolves and grizzly bears are a hot topic in the northern Rockies and many are looking to place blame on these animals making their living in the area. Studies done by both the state of Wyoming and Minnesota (which lost an entire population of 4,000 in the northwestern corner of the state) however are pointing towards a general trend in moose decline which has nothing to do with predation.
One of the key factors now being studied in these declines is in fact a general warming trend in temperatures throughout the moose states. Moose are a species of the north, there is no doubt about that. With the long hollow hairs and thick insulating undercoat that these animals carry around, even calves do not begin to feel the effects of cold until temps drop to negative 22 degrees. On the other hand, at 57 degrees adults begin to show signs of heat stress and at 68 degrees they have to begin panting to cool themselves down. With summer time temperatures in places like Jackson Hole now inching their way up the 90s at times during the summer months, could this be making the moose more susceptible to disease or having lower birth rates? As of right now, we do not have an answer to that question. What we do know however, is that based upon calf and cow survival rates, predation can be ruled out as a factor tipping the scales.
With the drop in temperatures down to the mid 50s as a high my first day in the park, this proved to be the spark that was needed to ignite the action all through the Greater Yellowstone Ecosystem. Moose, elk, black bears, grizzly bears, etc. . . all responded as predictably.
This bull moose came up out of the willow thickets down along the Gros Ventre river with his harem of three cows just before dawn and spent the majority of the morning feeding on rabit brush. Though I had scouted a larger bull that day, this one had the seclusion to allow me to work for hours on end without crowds. In terms of the experience, it doesn’t get better than that!