Squirrel monkey chuck call: vocal response to playback chucks based on acoustic structure and affiliative relationship with the caller

Abstract

Adult female squirrel monkeys (genus Saimiri) that are socially familiar often exchange the chuck vocalization, which differs acoustically across individuals. We used behavioral observations, vocalization playback experiments, and analysis of the acoustic properties of vocalizations to investigate the effect of caller identity and acoustic structure on vocal response to playback chucks in two all-female social groups (n=10 females). Females were most likely to respond with a chuck to the playback chucks of their closely affiliated partners compared to those of nonaffiliated group members. This shows for the first time that the chuck stimulus alone is sufficient to elicit a chuck response from a female's affiliated partner. Additionally, females responded with a chuck mostly to familiar playback chucks from their own group and least to playbacks of silent controls. Unfamiliar playback chucks from the same species and a different squirrel monkey species elicited chuck responses intermediate between familiar chucks and silent controls. Post-hoc discriminant function analyses provide preliminary evidence that females are most likely to respond to unfamiliar chucks when those chucks are close in acoustic structure to familiar chucks from their own social group. These results provide a provisional explanation for error in the squirrel monkey signal processing system, in which unfamiliar chucks never heard before nevertheless elicit a chuck response if they are similar in acoustic structure to familiar group chucks.

Chimpanzee Vocal Signaling Points to a Multimodal Origin of Human Language

“…Consistent with this idea, researchers have examined vocal exchanges between familiar individuals in close spatial proximity of one another in a number of nonhuman primate species [29], [31], [32], [33], [34], [35], [36], [37], [38]. The results of these studies suggest that this type of vocal exchange may share some characteristics with human conversation.…”

Structure and Usage of the Vocal Repertoire of Callithrix jacchus

“…We considered a vocalization as initial when it followed ≥10 s of vocal b silence and as a response when it was performed ≤4 s of an initial vocalization. We considered a behavior as a response when the subject performed it ≤4 s of an initial vocalization (Soltis et al 2002). In addition, we selected common behaviors to ascertain the behavioral contexts associated with certain vocalizations.…”

Integration of field and captive studies for understanding the behavioral ecology of the squirrel monkey (Saimirisp.)

“…Studies also have utilized wild populations, most of which have focused on affiliative vocalizations emitted by adult females, specifically chuck calls and peeps [Boinski & Mitchell, 1992Boinski & Newman, 1988]. Captive playback experiments have shown that adult females are more likely to respond to conspecific's chucks [Soltis et al, 2002] and that this exchange creates a distinct ''question'' and ''answer'' response [Biben, 1993;Biben et al, 1986] within a defined reply time period [Masataka & Biben, 1987]. Chuck calls are not discriminated based on behavioral contexts and instead are based on acoustic differences and answered with another chuck.…”

“…J. Primatol. Soltis et al [2002] showed that an auditory stimulus alone can elicit a chuck response, and therefore the monkeys do not need to see the caller. Much of primate vocalization is related to quiet affiliation contexts, which were not readily tested in playback experiments.…”

“…These calls provide mostly coordination of troop movement and maintenance of troop cohesion [Boinski & Mitchell, 1992]. Boinski and Mitchell [1992], Soltis et al [2002] Uses of olfaction Urine hand washing, evaluating estrous à ? Ability to detect monomolecular odorants, artificial odor mixtures, urine Boinski [1992b], Hudson [1993, 1995], Laska et al [ , 1996Laska et al [ , 2000, Ruiz [2005] Color vision polymorphism ?…”