Scientists have used this method to learn about many species, including elephants, small birds, whales and wolves. More than 700 wolves have been tracked in northern Minnesota in this way since 1968. First, a radio transmitter housed in a collar is attached to the animal. From a distance, the researcher uses a radio receiver and directional antenna to home-in on the signal and follow it to the collared animal. Wolves travel so far and wide that biologists usually use airplanes to track them.
Radio telemetry is used in several ways.
An activity detector in a special collar can be set to record the animal's activity over a 36-hour period. Data can be downloaded by the researcher, who sends a coded signal to the collar and then listens to the collar's reply. These special radio collars can also be equipped with darts holding a tranquilizer, which can be triggered from a distance. This allows researchers to easily recapture an animal. Satellites are being used in telemetry too.