DOW completes aerial survey of Western Slope deer herds

DOW completes aerial survey of Western Slope deer herds

May 8, 2001

BY THE COLORADO DIVISION OF WILDLIFE

DENVER — The Colorado Division of Wildlife, working in cooperation with sportsmen, has completed an aerial survey on the Western Slope that found survey systems used by Idaho wildlife managers produced deer population estimates similar to those developed by Colorado wildlife managers.

The survey was conducted at the request of Western Slope sportsmen who believe Division population models substantially over-estimate the size of deer populations on the Western Slope.

Representatives of the sportsmen joined forces with the DOW in conducting an aerial count using the Idaho system to help gauge the accuracy of the division’s own modeling and population estimates.

The Division aerial survey system estimated the mule deer population in unit 10 at approximately 6,800 deer while the Idaho model produced an estimate of 11,100 when adjusted for their sightability model. The Division uses computer models based on aerial counts and other information to estimate Colorado’s deer and elk population.

"We invited representatives of the Colorado Mule Deer Association to join us at the beginning of this survey," said Division Director Russell George. Members of both groups had questioned the Division techniques for estimating the size of the Western Slope’s deer herd.

"They joined us in designing the survey, we asked them where they would like the count to occur and what model we should use," George said. "They selected unit 10 and asked that we use the Idaho model.

"We also invited them to have experts of their choice participate at Division expense," George added. "Our goal was to build credibility in this effort from day one."

Wildlife managers from Colorado and Idaho and experts chosen by the sportsmen said the aerial surveys showed survey systems in both states provide similar estimates.

"We are confident that Colorado’s technique for counting deer provides conservative deer population estimates," said Division wildlife researcher Dave Freddy. "This aerial survey supported population estimates derived in our computer population models, and as such, support the concept that computer population models can provide reasonable estimates of population size to adequately guide decision making for managing mule deer."

The $50,000 study, funded in part by the Colorado Bowhunters Association and the Mule Deer Association, included the use of two helicopters flying 50 to 100 feet above the ground at 35 to 50mph. An observer and navigator joined the pilot in each aircraft and both Division biologists and experts chosen by sportsmen were included. The survey nearly ended in tragedy when one of the helicopters made a forced landing because of a mechanical problem.

"We were fortunate that no one was seriously injured," Freddy said.

Jim Unsworth, a principal wildlife research biologist at the Idaho Department of Fish and Game, assisted the Division with the survey.

"The estimates using our techniques tended to agree with those of Colorado," Unsworth said. "Colorado uses sampling techniques that are long-tested and are similar to what we use. We acted in a consulting form and were not out to prove that any estimate was right or wrong," Unsworth added.

Unsworth pointed out that cooperation between wildlife agencies is common and that Colorado researchers have assisted Idaho in the evaluation of their techniques.

Gary Miller, the Division terrestrial wildlife research leader, said the effort also allowed sportsmen to work directly with Division biologists and how deer populations are developed. "I hope that this project removed some of the uncertainty about our deer population estimates and it demonstrated how our wildlife managers and the wildlife profession works," Miller said.

"We continue to research, develop and test our management techniques," Miller added. "Our district wildlife managers and area biologists worked with us on this project, all working toward the same objective of improving our ability to manage Colorado’s wildlife."