Study: Northern Colorado Deer, Antelope Pops in Long-Term Decline

A new study by the National Wildlife Federation finds that deer and antelope in northern Colorado are in a long-term decline.

From this story in The Denver Post:

Deer and antelope populations in Colorado's northern mountain valleys have declined sharply over the past 30 years -- pronghorn by as much as 64 percent in some areas, mule deer by up to 36 percent -- according to a new National Wildlife Federation study. Colorado Division of Wildlife officials on Monday confirmed declines in the area from the Medicine Bow range west to Vermillion Bluffs -- a target for energy development. The NWF study concludes that herds across Colorado and southern Wyoming -- may not be able to fully recover -- unless federal and state agencies initiate larger-scale planning to protect their habitat.

Thoughts? Anyone care to suggest a potential reason for the decline?