TAIL FLAGGING BY YOUNG CALIFORNIA GROUND-SQUIRRELS, SPERMOPHILUS-BEECHEYI - AGE-SPECIFIC PARTICIPATION IN A TONIC COMMUNICATIVE SYSTEM

This report describes a field study of tail flagging by young Californ ia ground squirrels, and compares their behaviour to that of adults. F ocal and scan samples of marked animals were used to determine the con text of signalling, and to establish the behavioural concomitants of f lagging in the signaller and potential perceivers. Both pups and adult s invariably use this signal when encountering a snake, but both tail flag more often when there is no obvious elicitor (Hersek & Owings 199 3, Anim. Behav., 45, 129-138). When no snake was present, pups used ta il flagging in tonic communication, as adults did. Although tail flagg ing by adult females was related to the vulnerability of pups, signall ing by both adult males and pups reflected their own vulnerability. Ta il flagging by adult males and pups differed, however, in its effects on perceivers. Adult males induced nearby animals to maintain higher l evels of snake vigilance, while tail flagging by pups induced others t o remain nearby. Pups distinguished more clearly between contexts of t ail flagging than did adults. Both pups and adults tail flagged more f requently on days when snakes were on the site (than when snakes were absent), but this difference was greater for pups than for adults. Pup s were also more likely than adults to pair tail flagging with calling while dealing directly with snakes (as contrasted with flagging when no snake was present). Overall, the differences between pups and adult s appear to fit an age-specific interpretation of ontogeny. Pup use of tail flagging seems appropriate for their developmental stage, and do es not simply reflect an incompletely developed signalling system.