Activity Indices from Signal Modulation

William W. Cochran, 1308 West Main Street, Urbana, IL 61801-2307 USA and Larry L. Pater, U.S. Army Construction Engineering Research Laboratory, 2902 Newmark Drive, Champaign, IL 61821 USA

Automatic and continuous recording of the strength of signals from animal transmitters provided indices of activity that showed social relationships among individuals, circadian and seasonal activity patterns, nest attendance, time of death, and time of transmitter or attachment failure. Results were similar to those obtained from the commonly used "activity" transmitters that employ motion switches to modify pulse interval, but were obtained without the added size or cost of such transmitters.

The typically large data sets, e.g., many animal-years of data at 15-sec intervals, were easily handled on home-type computers. A real-time screen display showing current and previous activity for several hours alerted field workers of animal deaths.

Thunderstorms and high winds gave false indications of activity. Wind artifacts were successfully filtered in the analysis program, but data during thunderstorms had to be discarded.

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