Demographic Factors Are Associated with Intergroup Variation in the Grooming Networks of Female Colobus (Colobus vellerosus)

Social network dynamics, infant loss, and gut microbiota composition in female Colobus vellerosus during time periods with alpha male challenges

The gut microbiota of group-living animals is strongly influenced by their social interactions, but it is unclear how it responds to social instability. We investigated whether social instability associated with the arrival of new males and challenges to the alpha male position could explain differences in the gut microbiota in adult female Colobus vellerosus at Boabeng-Fiema, Ghana. First, we used a data set collected during May-August 2007 and May 2008-2009 that consisted of (i) 50 fecal samples from adult females in eight social groups for V4 16S rRNA sequencing to determine gut microbiota composition, and (ii) demographic and behavioral data ad libitum to determine male immigration, challenges to the alpha male position, and infant births and deaths. Sørensen and Bray-Curtis beta diversity indices (i.e., between-sample microbiota variation) were predicted by year, alpha male stability, group identity, and age. Next, we used a more detailed behavioral data set collected during focal observations of adult females in one group with a prolonged alpha male takeover and three cases of infant loss, to create 12-month versus 3-month 1-m proximity networks that preceded and overlapped the gut microbiome sampling period in that group. The long versus short-term networks were not correlated, suggesting temporal variation in proximity networks. In this group, beta diversity among the five adult females was predicted by similarity in infant loss status and short-term (rather than yearly) 1-m proximity ties. Although the mechanism driving this association needs to be further investigated in future studies, our findings indicate that alpha male takeovers are associated with gut microbiota variation and highlight the importance of taking demographic and social network dynamics into account.

Joint intergroup aggression in female colobus monkeys (Colobus vellerosus) is associated with grooming bonds, male participation, and group size

Cooperative home range defense is common in primates, despite a collective action problem that arises when group members benefit from winning the intergroup encounter regardless of whether they participate. The costs associated with this collective action problem may be mitigated by residing in small groups, residing with kin, or by forming strong bonds with group members. The potential to decouple the effects of these variables provided an opportunity to investigate which of these three variables best explains coparticipation in intergroup encounters among adult and subadult female colobus at Boabeng-Fiema, Ghana. Because males are often the main participants, we also investigated the relationship between female-female coparticipation and adult and subadult male participation. We collected intergroup behaviors from 94 adult and subadult individuals in eight groups during 1 year. We quantified female grooming bond strength and approach rates using focal samples. We classified female dyads as close kin (i.e., halfsiblings or more closely related) or nonkin based on partial pedigrees and genotypes generated from 17 STR loci. Female-female coparticipation was higher in dyads with stronger grooming bonds but was not associated with dyadic kinship, approach rate, or age class. Female coparticipation decreased with increasing female group size as expected if there is a collective action problem. Females coparticipated less in groups with more males and male intergroup aggression, possibly because there is less need for female-female cooperation if males are participating in the intergroup encounter. Females in smaller groups may not only benefit from increased female-female cooperation during intergroup encounters, they are also likely to reside with a higher-quality alpha male, both of which may increase the likelihood of winning intergroup encounters. There may be strong selection for facultative female dispersal in populations like the Boabeng-Fiema colobus in which small groups are associated with multiple benefits and cooperation is not affected by kinship.

Divergence in gut microbial communities mirrors a social group fission event in a black-and-white colobus monkey (Colobus vellerosus)

Host behavior and social factors have increasingly been implicated in structuring the composition of gut microbial communities. In social animals, distinct microbial communities characterize different social groups across a variety of taxa, although little longitudinal research has been conducted that demonstrates how this divergence occurs. Our study addresses this question by characterizing the gut microbial composition of an African Old World monkey, the black-and-white colobus (Colobus vellerosus), before and after a social group fission event. Gut microbial taxonomic composition of these monkeys was profiled using the V-4 hypervariable region of the bacterial 16S ribosomal RNA gene, and pairwise-relatedness values were calculated for all individuals using 17 short tandem repeat loci and partial pedigree information. The two social groups in this study were found to harbor distinct microbial signatures after the fission event from which they emerged, while these communities were not divergent in the same individuals before this event. Three genera were found to differ in abundance between the two new social groups: Parabacteroides, Coprococcus, and Porphyromonadaceae. Additionally, although this fission happened partially along lines of relatedness, relatedness did not structure the differences that we found. Taken together, this study suggests that distinct gut microbial profiles can emerge in social groups in <1 year and recommends further work into more finely mapping the timescales, causes, and potentially adaptive effects of this recurring trend toward distinct group microbial signatures.

Implications of Tourist-Macaque Interactions for Disease Transmission

During wildlife tourism, proximity or actual contact between people and animals may lead to a significant risk of anthropozoonotic disease transmission. In this paper, we use social network analysis, disease simulation modelling and data on animal health and behaviour to investigate such risks at a site in Morocco, where tourists come to see wild Barbary macaques (Macaca sylvanus). Measures of individual macaques' network centrality-an index of the strength and distribution of their social relationships and thus potentially their ability to spread disease-did not show clear and consistent relationships with their time spent in close proximity to, or rate of interacting with, tourists. Disease simulation modelling indicated that while higher-ranked animals had a significantly greater ability to spread disease within the group, in absolute terms there was little difference in the size of outbreaks that different individuals were predicted to cause. We observed a high rate of physical contact and close proximity between humans and macaques, including during three periods when the macaques were coughing and sneezing heavily, highlighting the potential risk of disease transmission. We recommend that general disease prevention strategies, such as those aimed at reducing opportunities for contact between tourists and macaques, should be adopted.