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Michael L. Casazza and Glenn D. Wylie, U.S. Geological Survey, Biological Resources Division, California Science Center, Dixon Field Station, 6924 Tremont Road, Dixon, CA 95620 USA

Understanding the activity patterns of animals can provide critical information needed to improve management and increase understanding of the biology of a given species. The recent development of remote data loggers facilitates the use of activity sensing radio transmitters in identifying diel activity patterns of animals. Motion sensitive transmitters were implanted in giant garter snakes (Thamnophis gigas) and activity patterns were measured on a 24-hr basis using a remote data logger (ATS, DC II Model D5041) telemetry receiver, and a single yagi (or omni directional) tower between 5 and 8 m high. Snakes were implanted with activity-sensitive radio transmitters which had a pulse rate of 45 bpm when stationery and much higher when active. Continuous monitoring of snakes by the data logger allowed for detection of intensity and duration of activity. Data recorded by the remote data logger included the date, time, frequency of the transmitter, and the number of pulses in a 10-sec interval. The number of pulses in the 10-sec interval indicated the activity level of the snakes. Snakes only having 7-8 pulses in a given interval were considered not active while 9-12 pulses indicated moderate movement and greater than 12 pulses was indicative of fairly rapid movement. Duration of movement was determined by looking at the number of consecutive 10-sec intervals with a pulse rate greater than 8. The biggest limitation in using this system was the range of the tower. Snakes which moved more than 500 m from the tower were often not detected and data were lost. The data logger was able to accurately record activity of the snake when it was in close proximity to the tower.