Activity recording of radio-tagged animals

A system for automatic activity recording of free-living animals instrumented for radio tracking is described. Technical details are given on a recorder, based on a frictionless transducer assuring extreme accuracy (Gould Brush 220 and 222). Activity separation from chart roll diagrams is possible for inactivity (resting, lying, etc.) and some activity performances like moving while foraging on a restricted area, steady movements of a walking pace, and rapid movements (running and jumping). Distinction between different activities could be done with an accuracy of less than 1 min. Examples from recorded data of an instrumented free-living roe deer and a mountain hare at the Grimsö Research Area are shown. For both species daily activity pattern is more or less related to sunrise and sunset, when activity reaches its highest value. Except for the roe deer in winter, day activity is lower than during night. The mean length of active periods in roe deer is fairly equal between winter and summer while mean length of inactive periods is significantly extended in winter. This could be explained by the digestive processes in relation to food quality.