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Behavioral endocrinology of wild male siamangs (Symphalangus syndactylus)
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Morino, Luca. Behavioral endocrinology of wild male siamangs (Symphalangus syndactylus). Retrieved from https://doi.org/doi:10.7282/T3T152D0

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TitleBehavioral endocrinology of wild male siamangs (Symphalangus syndactylus)
NameMorino, Luca (author); Palombit, Ryne (chair); Vogel, Erin (internal member); Trivers, Robert (internal member); Cachel, Susan (internal member); Katz, Larry (outside member); Lappan, Susan (outside member); Rutgers University; Graduate School - New Brunswick
Date Created2012
Other Date2012-10 (degree)
SubjectAnthropology, Siamang--Behavior--Endocrine aspects, Siamang--Research, Inter-male aggression
Extentx, 104 p. : ill.
DescriptionThe goal of my dissertation is to clarify the evolutionary forces shaping the behavioral and hormonal profiles of male primates. I collected more than 4,000 hours of focal behavioral observation and over 700 hormonal samples on five monogamous and six polyandrous groups of wild siamangs (Hylobatidae: Symphalangus syndactylus) in Sumatra (Indonesia), between August 2007 and May 2009. I addressed three basic aspects of gibbon sociality: 1. The monogamous social system of gibbons is thought to be maintained by intense male-male intolerance, yet in many populations there are numerous polyandrous groups. I test the hypothesis that dominance relationships regulate the interactions of adult male siamangs. Dominant males could clearly be identified in each group, based on a consistent direction of agonistic interactions, displacements and positional behavior. These males enjoyed greater social access to the resident female and monopolized copulations. 2. I tested the Challenge Hypothesis, which posits a correlation between male androgen levels, male-male aggression, and paternal effort. Results showed no association between male testosterone and group composition, male rank, or rate of intergroup aggression. Androgen concentrations were positively correlated with rate of intragroup aggression. Males involved in a period of social instability (an aggressive group takeover) had T concentrations twice above average. Males displaying active parental care had significantly lower testosterone concentrations than control males. These results represent a particularly valuable test of the Challenge Hypothesis due to the rarity of monogamous/polyandrous mammal species with paternal care. 3. An analysis of the aggressive takeover of three siamang groups suggests that: 1) variation in this species’ characteristic duetting is associated with periods of social instability; 2) takeovers represent a threat to vulnerable infants and forced weaning is used as an anti-infanticide tactic; 3) female ‘preferential’ social behavior toward one of the contenders influences the outcome of a takeover; 4) a secondary adult male in the group reduces the risk of being evicted for the dominant male. This research adds important pieces to our understanding of gibbon social organization, can help assess the generality of some human patterns (such as mate guarding, paternal care), and has important contributions to conservation efforts.
NotePh.D.
NoteIncludes bibliographical references
Noteby Luca Morino
Genretheses, ETD doctoral
Persistent URLhttps://doi.org/doi:10.7282/T3T152D0
Languageeng
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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