Citation. Figala, J.; Tester, J.; Seim, G. 1984. Analysis of the circadian rhythm of a snowshoe hare (Lepus americanus, Lagomorpha) from telemetry data. Vestnik Ceskoslovenske Spolecnosti Zoologicke 48:14-23.   [1048  LTER]

Abstract. The pattern of rest and activity of an adult male snowshoe hare was monitored over 26 months to illustrate seasonal changes in the circadian pattern. Data were collected in east-central Minnesota, U. S. A. using an automatic radio tracking system. Average daily percentage activity is used to define onset and end of activity in each 24 hour period. Phase-angle differences of onset, end and midpoint of activity and activity time show a strong similarity in successive years suggesting that telemetry data and our method of determining of onset and end are consistent and suitable for studies of rhythms in free-ranging animals. In general, onset followed sunset much more closely than end followed sunrise or midpoint followed darkness midpoint. Highest values of activity time occurred in winter and lowest values in summer. In terms of biological requirements, the large positive phase-angle difference in summer, with a short dark period, may indicate that the hare had to begin activity several hours before sunset to have sufficient time for feeding, grooming and other activities. During long winter nights the hare had ample time to complete required activities. Use of telemetry on free-ranging animals has the advantage of eliminating effects of cages and disturbances caused by human activities. Furthermore telemetry allows measurement of all locomotor movements, not just activity measured by running wheels, at food or nest boxes or on perches. In addition, telemetry provides an opportunity to determine how factors such as temperature, precipitation, food, cover and reproduction interact with photoperiod in determining the circadian pattern.