From the Field: Mule Deer Capture and Radio-Collaring

By Jim Lukens, Idaho Fish and Game Across the state, biologists will be capturing and collaring mule deer from the beginning of December through mid-January. This year the goal is to collar 66 does and 330 fawns statewide. In the Salmon Region, our goal is 11 does and 62 fawns. With a total of almost 1,000 active radio collars on mule deer in Idaho, we can determine survival rates, habitat use and migration patterns. Mule deer populations fluctuate primarily because of variability in fawn survival, which depends on body condition going into winter and winter weather. Doe survival rates are also important to track how populations are changing. Mule deer are captured using clover traps and drive nets. Clover traps are netted box traps baited with hay. Deer walk to the back of the trap to eat the hay and trip the door to slide shut. Drive nets are set up at the bottom of draws or in tall vegetation. A helicopter is used to herd the deer into the 6-foot-high nets where they are entangled. Helicopter drive netting is the safest way to capture deer even though it can occasionally be hard on the capture staff. Mortality of deer captured in drive nets is the lowest of any other capture method used for mammals, including box traps, leg hold traps, net-guns and drugging. The deer may be stressed for a short time, but this does not cause negative long-lasting effects. It is considerably quicker, though more expensive, to use helicopters to capture deer. When we capture deer, we weigh the trade-off between possibly harming an occasional deer with collecting reliable and sufficient data to manage populations. Once the deer are collared, we can locate them using a receiver and antenna. Each collar emits beeps on a specific frequency. During winter when deer move down to lower elevation winter range, the collars can be monitored from a vehicle traveling most roads. When deer return to the high country during late spring and summer, fixed wing aircraft are used to locate many of the animals. All collars have a mortality signal so that when an animal has died or stopped moving for four hours, the collar emits a beep rate at twice the speed of the "live" signal. Biologists can then access the carcass, retrieve the collar and usually make a determination of how the animal died. So, if you happen to see our helicopter herding deer on nearby hillsides, keep in mind that this is an efficient and essential tool for the management of our herds. Jim Lukens is the regional supervisor for the Salmon Region.