Marmosets (Callithrix Jacchus and C. Penicillata) as Prey: Behavioral, Hormonal, and Vocal Responses to Snakes.

摘要

Primates have evolved mechanisms to avoid predation including behaviors that aid in avoiding detection, preventing an attack, reducing predation risk, and fighting or escaping predators. The five studies presented in this dissertation examine the vocal, behavioral, and hormonal responses of two marmoset species when presented with snake models. The studies showed that mobbing calls (tsik) are structurally unique based on caller identity, although there are some potentially important acoustic changes over a period of six months. Despite the persistent individual differences in call structure, a playback study using numerical assessment was unable to show that marmosets actually use these individual call differences to identify conspecifics and assess caller reliability. The current research also found structural differences in the calls elicited by varying levels of predatory threat. Snake models of different sizes and proximity elicited tsik calls with significantly different acoustic parameters (duration and frequency) and indicated perception of degree of predation risk even when other behaviors (piloerection, scent marking, rate of calling, etc.) did not. A study of hormonal responses to a snake model was inconclusive and failed to replicate previous findings that linked cortisol levels with exposure to predator models. Altogether, these studies show that the mobbing vocalizations of marmosets have complex structural flexibility. More research is needed to determine if marmosets recognize their groupmates' vocalizations and to identify additional snake characteristics that are associated with altered call structure. Finally, there is a need to better understand the relationship between perception of predatory threat and cortisol levels in marmosets.