Predation, particularly by coyotes, has been proposed as a primary factor in the decline of mule deer throughout the West. The only certainty is that predators kill and eat mule deer. However, studies that investigated responses of entire mule deer herds to intensive coyote control have failed to demonstrate that mule deer numbers increased as a result of coyote control. The contribution of predation to the mule deer decline remains uncertain. Excessive deer harvests have been proposed as another primary cause of declining mule deer herds.
Studies show exactly the opposite patterns.
On the other hand, hunting has been a major factor contributing to reductions in numbers of bucks throughout Colorado deer herds over the past 3 decades. Yet, available evidence fails to substantiate that declining deer populations can be attributed to low buck numbers. Factors causing the current decline in mule deer numbers in Colorado and elsewhere are richly speculated but not well understood. Available evidence suggests that important deer habitats have deteriorated through time and that the current capacity of those habitats to support deer is now lower. Habitat effects are amplified perhaps by increasing elk numbers, disease, predation, and hunting, but very few experiments have been conducted to test for effects at scales of entire deer herds.