Abstract # 76:

Scheduled for Thursday, June 21, 2012 07:00 PM-09:00 PM: Session 9 (Gardenia) Poster Presentation


M. M. Petracca, J. A. French and N. G. Caine
California State University San Marcos, Department of Psychology, Lincoln, NE 68588-0308, USA
     Callithrix geoffroyi and C. penicillata are closely related Brazilian species with some overlap in range and occasional hybridization. We were interested to know if these two species, which presumably face similar predation pressures, have alarm calls that are acoustically distinct. Alarm vocalizations were recorded from captive marmosets in response to a model of a freeze-dried rattlesnake. Twenty calls from each of four adult C. geoffroyi and four adult C. penicillata (3 males and 1 female of each species) were randomly selected for preliminary spectrographic analyses. These analyses revealed species differences in the fundamental frequency, with C. geoffroyi having a higher starting and ending frequency. A discriminant function analysis confirmed that four acoustic variables (three measures of fundamental frequency and duration) distinguished between the two species [X2(4) = 88.75, p<.001]. Of the 160 alarm calls, 133 (83.1%) were correctly classified; only 80 (50%) would be correctly classified by chance alone [X2(1) = 72.25, p<.05]. The stability of classification was checked by cross-validation, in which 81.9% (131) of the alarm calls were correctly classified. The reliability and origin of these acoustic differences await confirmation and further analysis, but vocal distinctions such as these have important implications for understanding the complex taxonomic relationships and behavioral ecologies within the genus Callithrix.