The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Paternity confusion or reassurance? Why pregnant Hanuman langurs (Semnopithecus schistaceus) are proceptive


1Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, 2Department of Anthropology, Stony Brook University

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Anthropoid primates are unusual among mammals for their loss of estrus and for mating during gestation, which has been interpreted as a female counter-strategy to infanticide by males. If mating prior to conception is non-randomly distributed among males, after conception females may bias solicitations toward different males to confuse paternity and reduce the risk of infanticidal attacks. Under this tactic, males who join a group after a female has conceived should receive more solicitations than older resident males. Alternatively, pregnant females may solicit the same individuals to reassure males of paternity and encourage future protection of infants. We examined these predictions using proceptive behavior (i.e. solicitations of copulation via head shaking or presenting) before and after conception in Hanuman langurs from Ramnagar, Nepal. This species has no external signs of reproductive state, which may facilitate paternity confusion. Data were collected in ad libitum and focal animal sampling on two multimale, multifemale groups between 1991 and 1996. Groups had 4 to 15 adult females, and 2 to 9 adult males. A total of 2,542 proceptive events were included in the analysis. Post-conception, most females solicited different males (17 of 23 cases analyzed, 13 cases P<0.05, chi-square test). Further, when males joined a group post-conception, the new males generally received a higher percentage of proceptive behaviors (8 of 11 cases, 6 cases P<0.05, bootstrap analysis). These results support the hypothesis that proceptive behavior is aimed at paternity confusion. Future analysis will test whether proceptive behavior is indicative of the actual mating behavior.

Data collection was supported by the German Research Council (DFG: Vo 124/19-1+2; Wi 966/4-3), the Alexander von Humboldt Foundation (AvH), the German Academic Exchange Service (DAAD), and the Ernst Stewner Foundation.

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