Introduction

The extensive range of the gray fox (Canis [Urocyon]cinereoargenteus ), both in Latin America and the contiguous United States, as shown by Hall and Kelson (1959), suggests an ability to adapt readily to widely varying environmental situations. Hence, it is of value to learn how behavior varies in specific parts of its wide range.

Gray fox temporal activity is poorly understood. In 1972, an extensive gray fox literature review was conducted by Trapp and Hallberg (1974). At that time, the number of published references to fox circadian activity were limited to less than a half-dozen (Seton 1929; Grinnell etal . 1937; Taylor 1943; Gander 1966). With the exception of Taylor's (1943) work, little more than passing remarks were made concerning circadian activity.

In Texas, Taylor (ibid .) quantitatively described the activities of four captive animals during one 22-hour period. His conclusions generally agreed with those of Grinnell et al . (1937) in California and Seton (1929), who suggested crepuscular and nocturnal activity is most common.

Howver, Gander (1966), observed that gray foxes visited his southern California feeding station at all hours of the day and night, implying that diurnal as well as nocturnal activity is not unusual. A more recent and somewhat more quantitative investigation conducted from 1967 to 1969 in southwest Utah by Trapp (1978) concluded that: "Foxes, though active mostly at night, also forage diurnally and crepuscularly to a lesser, but important, extent."

Only limited information was available concerning gray fox home ranges. Richards and Hine (1953) in Wisconsin reported home ranges of 13–310 ha., while Lord (1961) in northern Florida estimated gray fox home ranges to be about 770 ha. Using telemetry techniques in southwest Utah, Trapp (1978) determined the mean home range to be 107 ha. It is not clear if the variation in home range size was due to differences in population densities (Trapp and Hallberg 1974), variations in habitat productivity, sampling errors, or other factors.

The present project's objective was to expand upon the temporal aspects of gray fox

[1] Paper presented at the California Riparian Systems Conference. [University of California, Davis, September 17–19, 1981.]

[2] Donald L. Hallberg is Associate Data Processing Analyst, California Department of Fish and Game, Sacramento. Gene R. Trapp is Associate Professor of Biological Sciences, California State University, Sacramento.

[3] New genus as suggested by Van Gelder (1977, 1978).

natural history by quantitatively describing circadian activity in relation to habitat utilization. Activity data were secondarily expected to provide information concerning home range and intraspecific interactions.

This paper is based on thesis research undertaken in 1973 (Hallberg 1974).