Age differences and developmental trends in alarm peep responses by Squirrel monkeys (Saimiri sciureus)

Alarm calls can code for different classes of predators or different types of predatory threat. Acoustic information can also encode the urgency of th reat through variations in acoustic features within specific alarm call typ es. Squirrel monkeys (Saimiri sciureus) produce an alarm call, known as the alarm peep, in highly threatening situations. Infant squirrel monkeys appe ar to have an innate predisposition to respond to alarm peeps but require e xperience to associate alarm peeps with the appropriate type of predatory t hreat [Herzog & Hopf, American Journal of Primatology 7:99-106, 1984]. Litt le is known about age-related differences in the type or frequency of respo nse to alarm peeps, or the development of alarm peep response in infants. T he purpose of this study was to test experimentally the response strategies of different age classes of squirrel monkey to the playback of alarm peeps that were produced by infants, juveniles, or adults. Results suggest that infants, juveniles, and female subadults respond more frequently to alarm p eeps than do adult females. Infant squirrel monkeys showed different behavi oral strategies in response to alarm peeps as a function of age. Adult fema les differentiate between infant and adult alarm peeps by responding more f requently to the alarm peeps of adult females. These data demonstrate that squirrel monkeys use acoustic information to discern when to respond to the alarm peeps from conspecifics, and that infants gradually develop an adult -like response to alarm peeps over the first year of development. Am. J. Pr imatol. 53:19-31, 2001. (C) 2001 Wiley-Liss, Inc.