Snowmobile activity and glucocorticoid stress responses in wolves and elk

The effect of human activities on animal populations is widely debated, particularly since a recent decision by the U.S. Department of the Interior to ban snowmobiles from national parks. Immunoassays of fecal glucocorticoid levels provide a sensitive and noninvasive method of measuring the physiological stress responses of wildlife to disturbances. We tested for associations between snowmobile activity and glucocorticoid levels in an elk (Cervus elaphus) population in Yellowstone National Park and wolf (Canis lupus) populations in Yellowstone, Voyageurs, and Isle Royale national parks. For wolves, comparisons among populations and years showed that fecal glucocorticoid levels were higher in areas and times of heavy snowmobile use. For elk, day-to-day variation in fecal glucocorticoid levels paralleled variation in the number of snowmobiles after we controlled for the effects of weather and age. Also for elk, glucocorticoid concentrations were higher in response to snowmobiles than to wheeled vehicles after we controlled for the effects of age, weather, and number of vehicles. Despite these stress responses, there was no evidence that current levels of snowmobile activity are affecting the population dynamics of either species in these locations.