Telemetry allows scientists to find the location of animals via remote sensing without continuously disturbing them. Animals in the 1960's, 70's, and 80's were primarily equipped with collars that emitted a radio signal. The animal's collar emits a radio signal that is detected with an antenna and a small receiver. The animal's position was then estimated.
Radio telemetry is cost effective and more reasonably priced than other alternatives.
However, scientists today can utilize satellites and computers to find the position of collared animals. Not only is it far more accurate, the collection of data can be made from very distant locations and multiple readings can be taken each and every day. Entire daily, weekly, and annual movements can be monitored. However, satellite collars and data retrieval are not cheap which can be an important factor in dealing with limited budgets. New break innovations are happening all the time with developments of better and smaller battery systems and many devices now utilize solar energy.