Seasonal variation in body weight, fat, and behavior of California ground squirrels (Spermophilus beecheyi)

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Abstract
Annual cycles of activity and reproduction were documented in a population of California ground squirrels (Spermophilus beecheyi) in coastal California [USA]. Behavior, body mass, and reproduction were monitored in marked individuals between November 1983 and January 1986 through regular focal animal observation and livetrapping. Mass measures for reproductive tracts and gonadal fat pads were concurrently collected from a separate population of animals sacrificed in the laboratory. Mass and feeding behavior varied with sex and age. Surface activity, body weight, fat pad, mass, and food consumption appeared to be closely related in this population. Fat pad mass was greater in nonreproductive than in reproductively active members of both sexes, as was body mass among males. Female body mass was greatest during pregnancy. Comparisons among reproductive status groups within each sex revealed significant differences in feeding, resting, vigilance, locomotor activity, and social behavior. Comparison with other populations suggested that S. beechevi is highly variable with respect to demography, seasonal activity, timing of reproduction, and social behavior.