Early auditory experience and the ontogeny of alarm-call discrimination in Belding’s ground squirrels (Spermophilus beldingi

Because young ground squirrels are vulnerable to predation, selection would favor the early ability to respond to alarm calls. This requires discrimination fclasses of alarm calls from each other as well as from non-alarm calls. Pre-emergent auditory experience may influence the development of discrimination. As a means of determining when Belding's ground squirrels (Spermophilus beldingi) can discriminate among calls, cardiac responses toalarm calls and control stimuli were recorded from 2 rearing roups that differed in the frequency of alarm-call exposure. Results uggest that before natal emergence, young can discriminate between 2 classes of alarm calls but they may not discriminate these calls from control stimuli. No differences inresponses were found between the rearing roups; thus experience with calls may not influence the onset of discrimination. Early discrimination may facilitate the rapid development of post-emergent behavioral larm-call responses. In many species of group-living birds and mammals, the appearance of a predator elicits vocalizations that can alert other animals of impending danger (for a review, see Klump & Shalter, 1984). These alarm calls may be especially important to individuals that have not already detected the predator, because the calls indicate that danger is imminent and quick action is required to reduce the likelihood of capture. Responding properly to alarm calls may be espe-cially important to immature young, because they are gen-erally more susceptible to predators than adults. Given that trial-and-error learning can be fatal, one might expect hat inexperienced young would be able to respond appropri-ately to alarm calls the first time they heard such calls. This expectation raises the question of when and how young develop adaptive behavioral responses to alarm calls. To display such responses, young must first be able to discrim