DOW Using Low-Flying Aircrafts in Mule Deer Study

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Low-flying helicopters will move across the Upper Arkansas River area over the next few weeks as Colorado Division of Wildlife (DOW) biologists and pilots put radio collars on mule deer as part of ongoing efforts to understand why herds have declined over the past decade.

The low-level flyovers will occur Jan. 8-20 west of Cañon City and then move north from Salida to Leadville in the mule deer study area. During the same period, helicopter pilots contracted by the DOW will also assist wildlife biologists as they conduct an annual mule deer count in the same region.

This is the fifth consecutive year for the radio-collar deer captures. Even so, regional biologists want to remind residents of the flyovers to ensure everyone understands why the helicopters are flying so low. Since Sept. 11, 2001, public interest in low-flying aircraft has heightened across the country, wildlife officials said.

During the capture process, helicopter pilots will fly over herds, drop nets over does and fawns, land and collar the animals quickly before freeing them. The fawn collars are designed to drop off after six months. The process helps biologists track the deer and gain insights into their migration and male-to-female ratios for game seasons.

However, the main reason animals will be collared is so biologists can glean insights into why mule deer populations have declined over the past decade. Radio collar transmitters enable biologists to check on deer from an airplane once a week. The signal changes when a deer dies, making it possible for a ground crew to locate the carcass, retrieve the collar, and try to determine the cause of death.

“This technique allows us to spread the captured animals over a large area, and it’s very quick. The negative impacts on the animals are minimal,” said DOW terrestrial biologist Jack Vayhinger. “It is less stressful on the deer than trapping, when animals are restrained for any length of time.”

Approximately 18 adult females and 60 fawns will be radio-collared over the next few weeks in an area roughly bordered by Leadville, Fairplay, Salida and Cañon City. Mule deer in Middle Park, the Craig area, and the Uncompahgre Plateau regions are also being studied. Biologists are studying mostly does and fawns, but also are taking a look at yearling bucks west of Gunnison.

“We observed some interesting migration patterns during the first four years of the program, but our primary goal is to determine survival rates,” Vayhinger said. “Doe and fawn survival rates are critical factors in the computer models we use for managing deer herds.”

Vayhinger said helicopter pilots contracted by the state would also participate in an annual survey of the state’s mule deer population, which entails low-level flying over fields and forests to count bucks, does and fawns. He said DOW biologists do not ride in helicopters because the flights can be challenging and pilots prefer not to carry extra weight. No pilot conducting herd surveys in Colorado has ever been killed in the process, but accidents have occurred in other parts of the West, he said.

“This part can be pretty exciting. It can be hazardous, too,” he said. “It takes an excellent pilot to do this. You have to watch for wires, trees and rocks.”