Variation of the Chip Vocalization of Three Species of Townsend Chipmunks (Genus Eutamias)

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Abstract
Sound spectrographic analysis was used to determine patterns of vocal variation in three species of chipmunks from northern California and Oregon. Recorded alarm-call vocalizations differed in Eutamias ochrogenys, E. senex, and E. siskiyou. The chip vocalization characteristic of E. ochrogenys consisted of paired syllables that varied little geographically. The call of E. senex was a rapid series of syllables that usually numbered three or four, with as many as 10. E. siskiyou produced a call with a single syllable, greater frequency range, greater intensity, and longer duration between calls than other species examined. Calls often are more distinctive and less variable in populations at species boundaries than in populations centrally located in species ranges. Calls from one particular population suggest that it may contain hybrid individuals. Together with evidence from morphometric, biochemical, and genital-bone studies, our examination of alarm calls in these three Eutamias taxa support their recognition as distinct species. In addition, the species boundary between E. senex and E. ochrogenys appears to be the larger Eel River rather than the ephemeral Van Duzen River as believed previously.