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Grooming Solicitation & Hierarchy
in Cercopithecus petaurista

By: Ryan Domitz | Mentor: Frank Logiudice

Introduction

Behavioral variation among primates, in concert with the effect captivity has on natural behavior, can interfere with the interpretation of a species' behavior. Wild populations can sometimes be difficult to study due to political or logistical difficulties. Therefore, a comprehensive understanding of primate behavior often necessitates both field and captive studies (Strier 2003). Like many primates, members of C. petaurista live in complex social groups and exhibit an array of communicative and hierarchal strategies. These behavioral strategies vary across the genus Cercopithecus (Nowak & Walker 1999) as well as within the order Primates.

Among behavioral strategies employed by C. petaurista, females exhibit a sexual solicitation known as "presenting," which involves approaching a male, turning their hindquarters towards the male, and simultaneously turning their head back to look at him (Morris, 2006). It should be noted that not all presenting behavior is sexually motivated. Presenting can also act as a greeting used to reduce aggression and is most commonly expressed by individuals of higher rank (Morris, 2006).

Agonistic behaviors known as threat displays involve staring with raised brows and typically the "tense-mouth face," "staring open-mouth face," and "silent bared-teeth face" (Morris, 2006). Some populations also display a head bobbing movement as an agonistic behavior (Central Florida Zoo). Grooming is also a form of socialization in primate groups and may confer social as well as antiparasitic benefits (Chiarelli, 1980). C. petaurista practices grooming, but studies have shown close kinship rather than hierarchy is indicative of grooming affiliations and aggressive responses between individuals (Schino, 2001; Chiarelli, 1980). Grooming between conspecifics can often be solicited in the form of lying down in the presence of a prospective grooming partner but does not necessarily initiate allogrooming, although the two may be correlated. There is also evidence that females, which tend to form more long-term relationships with conspecifics, practice more proportionate allogrooming than males do (Chiarelli, 1980). Interestingly, there as yet is no known direct correlation between grooming and aggression an individual exhibits in terms of hierarchy. Instead, subordinate individuals are more likely to perform allogrooming because confusing the identity of a grooming partner is of greater risk to lower ranked individuals; as a result grooming ultimately helps placate future aggressors (Chiarelli, 1980). Thus, individuals of similar proximity (both geographic and hierarchal) tend to belong to the same grooming associations and have been observed supporting their grooming partner in social conflicts (Chiarelli, 1980). This observation suggests that, in Old World primates, hierarchy is better measured in terms of the power of displacement one individual has over another than in terms of allogrooming received (Chiarelli, 1980). This implication, in turn, makes interpretation of the hierarchal stratum, a task crucial to managing captive populations, difficult. The present study thus asks whether allogrooming, grooming solicitations, and acts of aggression serve to maintain and identify hierarchy within captive populations of C. petaurista.

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