The daily distribution of activity has been studied in detail in ground squirrels in the field as well as in the laboratory, but studies of tree squirrels have been few and generally limited to the sampling of behavior of groups of animals. In this study, the authors investigated the general activity and nest occupation patterns of fox squirrels in a natural setting using temperature-sensitive data loggers that measure activity as changes in the microenvironment of the animal. Data were obtained from 25 distinct preparations, upon 13 unique squirrels, totaling 1385 recording days. Fox squirrels exhibited robust daily rhythmicity of locomotor activity, comparable to that of laboratory rats and gerbils. The animals were clearly diurnal, with a predominantly unimodal activity pattern, although individual squirrels occasionally exhibited bimodal patterns, particularly in the spring and summer. Even during the short days of winter (9 hours), the squirrels typically left the nest after dawn and returned before dusk, spending only about 7 hours out of the nest each day. Although the duration of the daily active phase did not change with the seasons, the squirrels exited the nest earlier in the day when the days became longer in the summer and exited the nest later in the day when the days became shorter in the winter, thus tracking dawn along the seasons. During the few hours each day spent outside the nest, fox squirrels seemed to spend most of the time sitting or lying. These findings suggest that fox squirrels may have adopted a slow life history strategy.

Collar temperature is in °C