Biotelemetry is a new tool that has become available to wildlife biologists within the past decade, thanks to recent advances in miniaturization of components such as transistors, mercury cell batteries, and printed circuits, allowing animals to be fitted with radio-collar transmitters. Current studies of toxic baiting for control of mountain beavers, jackrabbits, and nutria are employing this technology. The new technology expedites control evaluations and is far less costly than previous methods in obtaining needed data.