Wild wolves are difficult to study - they inhabit remote areas, range over large areas, and avoid people. By placing collars that contain radio transmitters on wolves, biologists can relocate wolves and gather a wealth of information on pack size, movements and territories, den locations, reproduction, kill rates, and many other facets of wolf ecology, biology, and behavior. In the last thirty years radio collars have unlocked many secrets of wolves that would have been impossible to learn without this technique.

Wolf radio collars contain a transmitter and battery pack sealed in a waterproof resin and an antenna that runs between layers of the collar material. After capturing a wolf with traps or by darting from a helicopter, the radio is fastened around its neck to be worn like a dog wears a collar. Each collar emits its own frequency so study animals are individually recognized. The batteries last up to three years. Transmitters must function in very cold temperatures, or when wet, and must absorb the punishment that results from a wolf running through the forest chasing prey. Some collars are chewed by other members of the pack, at times falling off as a result. By recapturing the wolf, collars can be replaced, and a wolf can be followed throughout its life and even retrieved after death to determine how it died.

Radio signals can be heard twenty-five miles away or more by biologists in airplanes equipped with antennas and receivers. This allows the plane to fly to and pinpoint the wolf's location. By circling overhead as low as 100 feet, biologists can determine the behavior of the wolves, count pack members, see the remains of kills, observe chases, and gather other data of interest. On the ground, signals can be heard from a mile or two away, adequate to determine presence or absence at a den or rendezvous site.