Vocal individual discrimination in Japanese monkeys

Abstract

The present study determines which features of the coo call are used by Japanese monkeys Macaca fuscata for vocal individual discrimination. First, two female Japanese monkeys were trained to discriminate conspecific individuals vocally, using an operant conditioning. Using as stimuli three unknown individuals with 30 calls per individual, the two monkeys succeeded in discriminating new call exemplars from the three stimulus individuals. A discriminant analysis performed on calls used as stimuli indicated that start frequency of the fundamental and call duration were variables that can differentiate individuals efficiently. Then, playbacks of acoustically modified signals were used to indicate which vocal features are used by monkeys for the individual discrimination. Stimuli signals containing modified pitch or duration, or filtered so as to keep only the fundamental component, were tested. Results indicated that Japanese monkeys use multiple acoustical cues to perform vocal individual discrimination, including at least pitch, call duration, and harmonics. However, harmonics seem to be less important for discrimination than pitch and call duration.

Individual recognition in a wild cooperative mammal using contact calls

“…In primates, older individuals consistently produce longer calls of lower fundamental frequency (Ey & Fischer 2007) and such differences in call pitch are known to be used by other species when discriminating between vocalizers (e.g. Ceugniet & Izumi 2004). When we plotted the fundamental frequency of the mongooses' contact calls against age we found a significant negative correlation (Fig.…”

Voice processing in human and non-human primates

“…Ceugniet & Izumi (2004a,b) used an operant conditioning procedure to train two captive Japanese macaques to discriminate the calls from three conspecific callers (30 vocalizations each). The macaques then were able to successfully transfer discrimination of identity when new calls from these three callers were introduced (Ceugniet & Izumi 2004b). Interestingly, the monkeys performed less well, but still above chance, when the calls had been low-pass filtered to preserve only the first harmonic, thereby eliminating cues to vocal tract filtering.…”

Acoustic cues to caller identity in lemurs: a case study

“…In nonhuman mammals, the acoustic structure of vocalizations usually differs according to factors such as species, individual identity, and social context (Taylor and Reby 2010). Individual recognition based on vocal signals is common in primates (Waser 1977;Rendall et al 1996;Mitani et al 1996;Ceugniet and Izumi 2004;Dallmann and Geissmann 2009), including lemurs (Oda 2002), and in other mammals (Sayigh et al 1998;Frommolt et al 2003;Vannoni and McElligott 2007;Charlton et al 2009). …”