ENVIRONMENTAL DETERMINANTS OF CIRCADIAN ACTIVITY OF FREE-RANGING IBERIAN LYNXES

From February 1983 to May 1985, 12 Iberian lynxes (Lynx pardinus) (six adults and six juveniles) were radiotracked at hourly intervals for 114 24-h periods at Donana National Park, southwestern Spain. Nine environmental factors were related, by season and age class, to 12 indices of daily activity of lynxes derived from movement rates and pulses of the motion sensor in the transmitters. Coefficients of determination were higher in winter and summer than in spring. Juvenile lynxes appeared more sensitive to environmental factors than adults. Photoperiod had a major influence (R2 = 29%) on circadian activity pattern throughout the year. Environmental factors significantly related to activity of lynxes during winter were maximum temperature, pressure changes, evaporation, and moonphase. In summer, important variables were maximum temperature, moonphase, hours with moonlight, and high pressures. In spring, only rainfall and temperature (minimum and maximum) showed a slight but significant influence on activity of lynxes. Although some climatological factors may have a direct effect on the circadian activity of Iberian lynx, others (e.g., moonlight) may act indirectly by influencing the activity of the Mediterranean rabbit, the lynx's main prey.