Determinants of response of wolf pups to auditory signals.

Two naive wolf pups (Canis lupus) were presented a variety of sound stimuli, including standardized recordings of natural and synthetic adult howls. The greatest and most consistent vocal response was elicited by the "real" howls. The nature of the response depended in part upon the i) type of stimulus, 2) number of stimulus presentations, 3) associated manipulations of context, and 4) individual differences in vocal responsiveness. Neither specific ongoing behaviors nor general activity levels of the pups appears to have mediated their vocal behavior. Differential responses demonstrated their ability to distinguish between recorded howls of adult wolves. Manipulation of the context, through presentation of either a human observer, live dog, or live mice increased the pups' vocalizations to the recordings. The results are discussed in terms of both extrinsic and intrinsic determinants of an animal's response to communication signals.