Assessment of telemetric motion sensors for studies of activity

Radio transmitters containing motion-sensitive devices that changed the pulse rate (mode) in response to movement were evaluated as a means for studying activity of black bears (Ursus americanus). Two types of motion sensors were used: tip switches gave immediate indications of activity, whereas reset motion sensors extended the active mode signal for 5 min. Locational accuracy was less affected by reset sensors than tip switches, and reset sensors facilitated activity monitoring of weak or fading radio signals. Tip switches were more useful in making continuous judgements of activity, and may be used to differentiate types and degrees of activity. For both sensors true activity could be distinguished from comfort movements. Also, both motion-sensitive transmitters gave indications of activity that compared well with hourly movements of bears; these transmitters were more sensitive to localized movements than measurements between radio locations determined by triangulation and were more practical because only one observer was necessary. Motion sensors also gave more reliable indications of activity than changes in signal integrity.