Tail flagging by adult California ground squirrels: a tonic signal that serves different functions for males and females

Abstract Abstract. This report describes a field study of naturally occurring tail flagging by adult California ground squirrels, Spermophilus beecheyi beecheyi. Squirrels invariably used this visual anti-snake signal when encountering a snake, but used it more often when there was no obvious elicitor. Focal and scan samples of individually marked animals were used to determine when and where squirrels tail flagged, and to establish the behavioural concomitants of flagging in the signaller and nearby potential perceivers. The results presented here indicate that tail flagging is a functionally and structurally diverse activity that is used in both tonic and phasic time scales. Tonic use of spontaneous tail flagging by maternal females covaried with the changing vulnerability of pups, but such tail flagging by males reflected their own vulnerability. Related to this functional difference is evidence that spontaneous tail flagging by 'selfish' males and 'nepotistic' mothers differed in its impact on perceivers. Male tail flagging appeared to have an effect on both pup and adult perceivers, whereas tail flagging by mothers seemed to affect only adults. (Insufficient data were available to judge the impact of a mother's flagging on her own pups.) When dealing directly with snakes, however, males and mothers may have converged upon similar phasic uses of tail flagging. In this context, distinctively high rates of tail flagging and calling may be used by both males and mothers to achieve the relatively immediate benefits associated with recruiting others to the vicinity of a snake.