Differences in Diet Between Six Neighbouring Groups of Vervet Monkeys

The comparative approach provides a powerful tool to study evolutionary questions on both intra‐ and interspecific variation. It has been applied to a great variety of taxa, including primates. Primate studies differ from those on most other taxa in two ways: first, data from most study sites contain information about only one group. Second, primatologists have used the comparative approach also to identify local traditions, that is, behaviours that spread through social learning. Here, we evaluate the appropriateness of such data by comparing the diet composition of six neighbouring groups of vervet monkeys, Cercopithecus aethiops. We used scan samples to collect diet data, and abundance measures and phenology to assess the availability of the 14 most important tree species utilised during the study. We calculated indices of diet overlap, which were highly variable and could be remarkably low. Furthermore, we found significant differences between group diets with respect to the relative utilisation of 13 of the 14 tree species. For all 13 species, we found positive correlations between local abundance and appearance in the diet, consistent with the importance of local ecology for diet composition. Nevertheless, more detailed comparisons of pairs of groups often revealed significant mismatches between the relative importance of a tree species and its local abundance. In conclusion, local variation merits increased attention by primatologists. While our results are compatible with the possibility that traditions exist on a local (group) rather than population scale, alternative explanations have to be considered.     

Selection of secondary growth areas by vervet monkeys (Cercopithecus aethiops)

Habitat selection by a group of vervet monkeys (Cercopithecus aethiops) living on the savanna peninsula of St. Kitts was investigated by the intensive sampling of 12 transects. The vervets exhibited nonrandom use of habitats. Examination of 20 ecological variables in each of the habitat types revealed that the vervets preferentially used areas of secondary growth characterized by high density and diversity of tall food plants. It is suggested that the preferential use of secondary growth habitat can be attributed to the fact that these areas have high levels of plant productivity and that they have a large proportion of their productivity available for consumption.     

Formidable females redux:male social integration into female networks and the value of dynamic multilayer networks

The development of multilayer network techniques is a boon for researchers who wish to understand how different interaction layers might influence each other,and how these in turn might influence group dynamics.Here,we investigate how integration between male and female grooming and aggression interaction networks influences male power trajectories in vervet monkeys Chlorocebus pygerythrus.Our previous analyses of this phenomenon used a monolayer approach,and our aim here is to extend these analyses using a dynamic multilayer approach.To do so,we constructed a temporal series of male and female interaction layers.We then used a multivariate multilevel autoregression model to compare cross-lagged associations between a male's centrality in the female grooming layer and changes in male Elo ratings.Our results confirmed our original findings:changes in male centrality within the female grooming network were weakly but positively tied to changes in their Elo ratings.However,the multilayer network approach offered additional insights into this social process,identifying how changes in a male's centrality cascade through the other network layers.This dynamic view indicates that the changes in Elo ratings are likely to be short-lived,but that male centrality within the female network had a much stronger impact throughout the multilayer network as a whole,especially on reducing intermale aggression(i.e.,aggression directed by males toward other males).We suggest that multilayer social network approaches can take advantage of increased amounts of social data that are more commonly collected these days,using a variety of methods.Such data are inherently multilevel and multilayered,and thus offer the ability to quantify more precisely the dynamics of animal social behaviors.     

Spectral sensitivity of vervet monkeys (Cercopithecus aethiops sabaeus) and the issue of catarrhine trichromacy

Several genera of platyrrhine monkeys show significant polymorphism of color vision. By contrast, catarrhine monkeys have usually been assumed to have uniform trichromatic color vision. However, the evidential basis for this assumption is quite limited. To study this issue further, spectral sensitivity functions were obtained from vervet monkeys (Cercopithecus aethiops sabaeus) using the technique of electroretinographic flicker photometry. Results from a chromatic adaptation experiment indicated that each of the twelve subjects had two classes of cone pigment in the 540/640 nm portion of the spectrum. That result strongly suggests that this species has routine trichromatic color vision. Comparison of the spectral sensitivity functions obtained from vervets and from similarly-tested humans further indicates that the cone complements of the two species are very similar. Results from this investigation add further support to the idea that there are fundamental differences in the genetic mechanisms underlying color vision in platyrrhine and catarrhine monkeys.     

Diet and dominance among female vervet monkeys (Cercopithecus aethiops)

Behavioral observations of free-ranging female vervet monkeys (Cercopithecus aethiops) suggest that priority of access to food enhances individual fitness. Seventeen adult females living in two social groups were observed for 26 months in the Samburu/Isiolo Game Reserves, northern Kenya. Priority of access to feeding and sitting sites was associated with significant differences in diet and reproduction. Food species distribution altered rank-related differences in diet. Rank-related differences in diet occurred when food items were clumped in distribution, but not when they were randomly distributed. The relation of individual food items to reproduction influenced rank-related differences in reproduction. Rank was significantly correlated with birth rate when a preferred food species was clumped in distribution.     

Acute changes in social composition and agonistic behavior in male vervet monkeys (Cercopithecus aethiops sabaeus)

Among nonhuman primates the composition of social groups influences the interactions of group members. We assessed the effects of acute changes in social composition on behavior among 15 adult male vervet monkeys (Cercopithecus aethiops sabaeus). Subjects were observed in their basal social groups which comprised 3 adult males, 2–4 adult females, and offspring; and in two subgroups consisting of either two or three adult males. Agonism and vigilance increased in smaller groups relative to basal conditions, while subjects in two-male groups displayed more aggression than those in three-male groups. These findings suggest that, among male vervet monkeys, acute disruption of stable social groups increases aggressive behavior, and that the amount of agonism is influenced by the composition of the consequent subgroups. © 1992 Wiley-Liss, Inc.     

Twinning in a colony of vervet monkeys (Cercopithecus aethiops sabaeus)

From 1975 through 1991, three sets of twins were born from a total of 693 live and stillborn births (0.43%) at the UCLA/Sepulveda Veterans Administration Medical Center Nonhuman Primate Research Laboratory, CA. None of the twin's mothers were related. Positive patrilineal relationships have not been established; however, a brother (not a twin) of the first set of twins may have fathered the third set. All twins were born to multiparous females and, in each case, only one infant survived beyond 4 days. One set of twins was dizygotic; the genetic status of the others is unknown. © 1994 Wiley-Liss, Inc.