Ontogeny of swift fox Vulpes velox vocalizations: production, usage and response

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Three processes, production, usage, and response, can be used to describe vocal ontogeny. They may develop independently of each other for a given vocalization and a given species as a result of the different selective pressures associated with each process. We have investigated vocal ontogeny in the swift fox Vulpes velox, using recordings and observations of captive foxes from the time of natal den emergence (age 3-4 weeks) to the time of natal dispersal in the wild (age 4-5 months). We first classified adult vocalizations used during the mating and pup rearing seasons into vocal types (19 types in total) and found that swift foxes have a vocal repertoire comparable in size and diversity to other canids. The repertoire of juvenile foxes contained 16 of the 19 adult-type vocalizations and one juvenile vocalization by age 10 weeks, after which no new types appeared by the end of the study period. Two of the 3 adult vocalizations not observed in juveniles appear to be associated with mating and possibly territoriality and the third is a high intensity alarm vocalization. Apart from 3 vocal types (1 alarm and 2 non-agonistic), once vocalizations had appeared in the juvenile repertoire, they did not seem to change in context over time. Juvenile responses to 5 vocalizations emitted by adults (3 alarm, 1 agonistic, and 1 non-agonistic) appeared to change with increasing age to approach adult-type responses. The emergence of these adult-type responses to 2 of the 3 alarm vocalizations coincided with their first appearance in the juvenile repertoire. The results indicate that there is variation in the degree (in terms of the number of vocal types) of modification over time among the three processes.
Original languageEnglish
Issue number6
Pages (from-to)659-681
Publication statusPublished - 2006

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