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We investigated the genetic structure and kinship patterns of black howler monkeys ( Alouatta pigra) at Palenque National Park, Mexico. Fecal samples from 49 individuals residing in eight social groups were successfully genotyped for 19 polymorphic microsatellite markers known to be variable in other ateline primates. Overall, genetic diversity was low ( Ho = 0.588) with an average of 4.2 alleles per loci (range = 2-8). We found that intergroup genetic variation among adults was relatively high (mean between-group FST = 0.119), largely due to the genetic divergence of one study group from the others. Intragroup kinship patterns showed that in most social groups, either adult males, adult females, or individuals of both sexes resided with same-sexed adult kin, suggesting that some black howler males and females may not disperse from their natal group or may disperse with related individuals. Of the six sampled immigrant males, two males joined established groups by themselves, and four males formed two pairs that each took over the social group they joined after evicting the resident males. Males in both these coalitions were genetically closely related, while the two solitary immigrants were not closely related to any of the resident males present in the group they joined. Am. J. Primatol. 74:948-957, 2012. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We investigated the social relationships among adult females in two multimale-multifemale groups of black howler monkeys Alouatta pigra during a 14-month study in Palenque National Park, Mexico. Based on over 900 focal hours and over 5400 scan samples recording neighboring group members, we found that females very rarely engaged in agonistic interactions and no dominance hierarchy could be discerned. Relationships among resident females were primarily affiliative, but females of one study group spent a higher proportion of time in close proximity and engaged in affiliative interactions with one another at higher rates than females in the other study group. The strength of female relationships increased with the birth of an infant. Although no females immigrated during the study period, the temporary association of three extragroup females with our study groups implies that the social system of black howler monkeys is more dynamic than previously suggested. These findings suggest that female black howler monkeys behave more similarly to female red howler monkeys A. seniculus than to female mantled howler monkeys A. palliata [Current Zoology 57 (1): 1-7, 2011]. [ABSTRACT FROM AUTHOR]

We studied two multimale–multifemale groups of black howler monkeys (Alouatta pigra) during a 14-month study (June 2006–July 2007) in Palenque National Park, Mexico to evaluate the ways in which their sexual behavior changes across ovarian cycles. We analyzed 231 fecal samples, collected every 2.2±1.4 days from five females. For four females, estradiol and progesterone profiles revealed an average (±SE) cycle length of 18.3±1.4 days. Copulations occurred significantly more frequently during the periovulatory period (POP), defined as the estimated day of ovulation ±3 days (N=18). This was largely the result of cycling females soliciting sexual interactions during their POPs. Females directed their solicitations significantly more often toward “central” males of their group, who had close spatial associations with females at other times, compared with “noncentral” males, who did not associate closely with females. Central males rarely solicited sexual interactions, but instead monitored the females' reproductive status by sniffing their genitals, and maintained significantly closer proximity to females during their POPs, suggesting male mate guarding when conceptions are most likely to occur. Our findings indicate that the reproductive strategies of black howler central males and females coincide, highly skewing mating opportunities toward central males. Black howler females, however, occasionally choose to copulate with noncentral resident males or extra-group males during their POPs, undermining the ability of central males to monopolize all reproductive opportunities. Am. J. Primatol. 71:153–164, 2009. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]