Classification of Captive North American River Otters (Lontra canadensis) Vocal Repertoires: Individual Variations, and Age Class Comparisons

Abstract

This is the first study to examine in detail the vocal behaviors of North American river otters (Lontra canadensis), and the results suggest that river otters have complex vocal repertoires comprised of four distinct vocal types and seven sub-call types. The vocalizations and behaviors of ten captive North American river otter adults, one litter of newborn pups and one litter of pups at eight weeks old were recorded using a SONY Handheld DV camera and an infrared surveillance system. A quantitative analysis of 2726 calls on the adults and 299 calls for the pups was conducted for acoustic parameters that included frequencies, powers, and duration. Whine, chirp and chatter call types were the main vocal elements of the vocal repertoire and were present at birth. Pups vocals were structurally underdeveloped versions of the adult vocals and adults call types showed individual variations. This suggests that vocalizations are likely individually modified as pups enter adulthood. A unique whistle was present in newborn pup vocal repertoires but appeared to be reduced in the repertoire by eight weeks old. However, further research needs to be conducted to determine the function of the whistle.