Fall and winter rains grow forbs, plants we think of as weeds but which pronghorns find highly nutritious. When the rains fail, as they frequently have over the last decade, whole herds of pronghorns can starve. Human activities also share the blame for declining numbers of pronghorns. Insufficient rainfall also translates to insufficient concealment for fawns in late spring and early summer. Since the late 1980s, fawning cover has been very limited in the Trans-Pecos.
Predators detect movement to locate prey.
Without herbaceous cover, a significant number of fawns annually fall prey to coyotes within 30 days of birth. They are lying out there on what amounts to a huge parking lot. Anytime they raise their heads, a coyote can see them from a mile away. Fences also work against adult pronghorns trying to escape from coyotes. Coyotes have learned to use fences to slow or stop pronghorns and catch them.