Gunners, Muggers and Trackers

Adrenaline Junkies of Big Game Research, By George Pauley Gunners, muggers, and trackers - common phrases used by wildlife biologists to describe their adrenaline-junky coworkers who enjoy the high-risk adventure of big game research. Flying around in a helicopter without doors, a gunner fires an expanding net onto an elk. The net entangles the animal, and then the mugger jumps out of the helicopter to restrain it. The mugger and a biologist then blindfold and hobble the 400-pound animal, secure a radio collar around its neck, collect blood and fecal samples, examine its teeth to estimate the animal's age, and finally, untangle it from the net - all in about twenty minutes if everything goes according to plan. While gunners and muggers are often kicked, gouged and bruised, the duties of trackers who often follow the movements of radio-collared animals for extended lengths, are more of study and observation. Radio collars allow researchers to study wild animals without actually having to get close enough to see them thus eliminating or reducing the risk of the animal changing its behavior. Since they were first used, radio telemetry devices have become one of the most important tools in wildlife research. Most collars are equipped with a narrow band radio that transmits a unique frequency allowing specific, individual animals to be monitored or located. One of the more common objectives of radio telemetry is to obtain animal locations. Location data is used to evaluate habitat use, migration patterns, movements and home range areas. The usual method of locating a transmitter is to use a directional antenna, either from the ground or from airplanes. The directional antenna, which is similar to a TV antenna, yields the strongest signal when pointed directly at the transmitter. The animal is located by merely following the strongest signal. An equally common use of telemetry is to determine whether specific animals are alive or dead. Mortality sensors incorporate a timer and a mercury- activated switch. While the animal is alive and moving, the mercury flows back and forth, resetting the timer. Once the animal dies, the timer runs a pre-determined time and then resets the radio transmission rate. In most applications, the radio transmits a signal 75 times each minute, and in mortality mode the transmission rate increases to 150 times per minute. Subsequently, the researcher can locate the dead animal to determine the cause of death. This type of data is used to determine the importance of different sources of mortality and to determine survival rates for populations. The most simplistic radio collars have a VHF-transmitter with a unique frequency and mortality sensor. More sophisticated collars include a Global Position System (GPS) device. On pre-programmed intervals, the GPS determines the location of the animal and records the coordinates on a memory chip. Some GPS collars can be remotely downloaded with a radio receiver, while others must be retrieved and manually downloaded. There are also versions of GPS collars that transmit coordinate data to satellites. The data is subsequently downloaded to internet websites where it is accessible. The obvious advantages of GPS collars is that large numbers of precise locations can be generated without the costs of obtaining locations via ground methods or with more costly aerial surveys. However, as you might expect, GPS collars are much more expensive. Although, if the objective of the work involves many locations, GPS collars are by far the most cost effective approach. Another disadvantage is that the additional electronics of GPS collars require additional battery power which greatly limits battery life. The weight of the color and radio also limits the use of some radio telemetry equipment. We obviously need to keep weights at a level that does not hinder the animal or cause discomfort. A common rule of thumb is a maximum weight of two percent of the animal's body weight. For animals such as elk, this is a fairly liberal guideline given that an average cow weighs around 400 pounds and two percent is eight pounds of radio collar. In practice, we rarely use anything that large. The elk radio collars we presently use for the statewide big game study weigh slightly over one pound. These collars include enough battery to power the radio for five to seven years. Finally, we are frequently asked by hunters if it is legal to harvest a radio-collared big game animal during hunting season. The answer is yes. Don't hesitate to harvest a collared animal. Remember, a common objective of research is to measure various sources of mortality, including hunting. George Pauley is a research biologist with the Idaho Department of Fish and Game. He is presently working on the statewide mule deer and elk research effort.