The behavioral ecology and population genetics of pronghorn (Antilocapra americana) in Yellowstone National Park, Montana/Wyoming, USA.

摘要

Yellowstone National Park's northern range is home to an isolated and vulnerable population of pronghorn (Antilocapra americana ) greatly reduced from historic levels of abundance and at severe risk of extirpation. Yellowstone pronghorn are partially migratory, with >70% of the pronghorn population migrating 15-50 km to interior summering areas and 30% remaining year-round on the winter range. Most females show fidelity across years to their migration strategy and summer use area, but approximately 20% switch migratory strategy between years. Incomplete post-natal dispersal results in weak genetic substructure of this population. Evidence for an historic genetic bottleneck in the population is strong. However, Yellowstone pronghorn retain substantial genetic diversity. Most current measures of adult female condition are within the ranges of healthy populations elsewhere. However, fawn mass at birth is low, indicative of reproductive depression potentially due to changes in winter diet composition or spring/summer forage quality. Fawn age at death is correlated with fawn condition at birth, and fawn condition and age at death are significantly greater for migrants than for non-migrants. Predation is the chief proximate cause of fawn mortality, with coyotes accounting for up to 79% of pronghorn fawn predation. Cougars, black bears, and golden eagles kill fawns on rare occasions. The impact of wolf presence on fawn survival is positive in low-elevation areas where coyotes are abundant and negative in high-elevation areas where coyotes are scarce, supporting predictions of a coyote-mediated effect of wolves on pronghorn reproductive success. Results suggest that deep winter snow, in conjunction with mobility constraints imposed by reproduction in coyote populations, may lead to the formation of high-elevation refugia for migrant pronghorn in Yellowstone.