Photo Credit: Aaron Rinker, USFWS
Photo Credit: Aarron Rinker, USFWS

Visitors to Rocky Mountain Arsenal (RMA) will begin to notice that one of the most obvious wildlife features of this National Wildlife Refuge will be donning some new clothes. Beginning this spring, biologists at RMA will be trapping and darting Mule and White-tailed Deer as part of an on-going study to determine why the deer herds are producing fewer fawns.

“In the late 90’s we noticed that fewer fawns were showing up in our annual fall surveys,” says biologist Sherry Skipper, who heads up the study. “Our population is unusual in a number of ways. We have a fence around RMA that prevents deer from getting in or out. And there is currently no hunting on the refuge.” Skipper goes on to say that the scarcity of fawns may be due to several reasons. One reason may be that nutritional deficiencies during the winter are causing does to have fewer young. RMA, which is the site of on-going environmental cleanup, has large areas that are temporarily unsuitable deer habitat until native grassland vegetation can be reestablished.

Another possibility is that the population has aged because older deer have survived longer without hunting. These older deer, both bucks and does, are less able to produce fawns. Still a third possibility is that the coyote population has grown and is preying more on young fawns, especially as their main prey, the prairie dog, has declined due to recent outbreaks of plague.

A fourth possibility is that the recent years of drought have taken its toll on young fawns or altered the vegetation so that fawns are more vulnerable.

“These, or any combination, are all reasonable explanations,” says Eric Stone, another biologist working on the project. “What we need to do is to find out if the does are pregnant. Then follow them until they give birth to fawns. And then follow the fawns to determine if they survive and what the causes of mortality are.” Skipper and Stone hope that by tracking the deer with radio-transmitters they can eventually find out what is causing fewer fawns to survive and whether intervention is needed.

So if you see a deer wearing a collar, now you will know it is part of an investigation. Like a detective story, this one may not be solved until the end of the book. But the collar is a means of collecting the clues we need to solve the RMA deer mystery.

Last Updated: 3/24/09