Relationship between daily body temperature and activity patterns of free-ranging feral cats in Australia

Daily rhythms of body temperature (T_b) and activity (distance travelled) of eight free-ranging feral cats (Felis catus) were recorded via implanted body temperature loggers in conjunction with Global Positioning System technology (GPS-radio collars), over a period of 14 days. The calculation of distance travelled (as a measure for activity) from GPS-data points proved to be efficient to quantify the relationship of both variables under field conditions. Analysis of covariance (ANCOVA) was employed to disentangle the relative effects of activity and time of day on T_b. Most variance in T_b was explained by time of day (with distinctly higher T_b at night), while considerably less variation was explained by distance travelled. Most importantly, the correlation between distance travelled and T_b was significantly stronger during daytime than at night. Indeed, night-time T_b showed little fluctuation at all. Taken together, the results suggest that the circadian T_b rhythm is primarily generated by an endogenous oscillator and that high T_b during night-time are not driven by high(er) nocturnal activity.