In 1999, the Division embarked on a collaborative plan with Idaho Fish and Game to undertake a series of research projects to examine the role of predation and nutrition on mule deer survival. Colorado was not positioned well to implement intensive predator control because of socio-political concerns and Amendment 14, which eliminated trapping, snaring and coyote-getters as control tools. Therefore, Idaho agreed to conduct predator-control research while Colorado focused on habitat and nutrition investigations.
Habitat research conducted by the Division demonstrated that mule deer populations on the Uncompahgre Plateau were limited by the quality and quantity of winter range forage.15 A follow-up study found that removing pinyon-juniper trees and spraying weeds increased winter fawn survival.16
Idaho Fish and Game concluded their part of the joint collaboration in 2011. The Idaho Fish and Game Department spent $249,000 on coyote control over a six-year period and found no evidence that mule deer populations increased as a result of coyote control. On the other hand, the removal of mountain lions corresponded to a reduction in winter mortality of adult female mule deer. Mountain lion removal increased fawn ratios and their models predicted fawn ratios would increase 6% at average with removal rates of approximately 3 lions per 330 square miles and increase 27% at maximum removal rates of approximately 14 lions per 330 square miles. However, they did not detect a strong effect of coyote or mountain lion removal alone on mule deer population trend. Instead, the study concluded that winter severity and summer precipitation were the most important influence on mule deer population growth.13
Utah has initiated aggressive programs to manage predators. In 2012, the Utah Legislature approved a $5 surcharge on hunting licenses to fund predator control. During the past six years, the Utah Division of Wildlife Resources has transferred $3.4 million to the Utah Department of Agriculture for predator control, much of that in an effort to bolster declining deer herds.14
In the Piceance Basin, wildlife researchers have focused on implementing and evaluating habitat treatments and best management practices as strategies to maintain mule deer numbers in areas where energy development is occurring, with the cooperation and support of multiple energy companies.20
CPW wildlife researchers area also conducting the first spatial and temporal analysis of the landscape changes that have occurred to mule deer habitat across western Colorado. Specifically, they will determine the amount of deer habitat that has been lost to different types of human land uses (i.e. development), and potentially degraded due to fire suppression and long-term trends towards warmer, drier weather. The changes to western Colorado's habitat that have occurred from ~1970 to present will be quantified. The past 40 years includes a notable in decline in deer numbers, and there are comparable habitat data available across this time period.21