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 1 14 24-h periods at Donana National Park, southwestern Spain. Nine envi ronmental 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 appea red more sensitive to environmental factors than adults. Photoperiod h ad a major influence (R2 = 29%) on circadian activity pattern througho ut the year. Environmental factors significantly related to activity o f lynxes during winter were maximum temperature, pressure changes, eva poration, and moonphase. In summer, important variables were maximum t emperature, moonphase, hours with moonlight, and high pressures. In sp ring, only rainfall and temperature (minimum and maximum) showed a sli ght but significant influence on activity of lynxes. Although some cli matological factors may have a direct effect on the circadian activity of Iberian lynx, others (e.g., moonlight) may act indirectly by influ encing the activity of the Mediterranean rabbit, the lynx's main prey.