DESCRIPTION: Overall tan or reddish-tan, with white on sides, rump, belly, chest, inner legs, cheeks, and lower jaw. Both sexes have black pronghorns, with the male's 12-20" (30-50cm) long and the female's only 3-4" (7.5-10cm) long at best.
NATURAL HISTORY: Herbivorous. Active both day and night. Form large herds during the winter, breaking into smaller herds (both bachelor male and small female herds) in summer. Mating system used is both female defense and resource defense polygyny (see Mating Systems below). The subspecies we have (A. a. sonoriensis) is federally endangered; factors negatively impacting their populations include habitat loss/alteration, fencing (they resist jumping over fences), and increased coyote predation on fawns (likely partly due to habitat alteration). Pronghorn are the fastest land animal in the Western Hemisphere and among the fastest in the world, attaining speeds of 45 mph (70 kph). Cheetah predation during the Pleistocene likely selected for their great speed (the cheetah's have since gone extinct in North America). Pronghorn run with their mouths open to force-feed air into their lungs for greater endurance.