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Tinsley Johnson, E.

Publications and source records attributed to Tinsley Johnson, E..

2 recordsLinked to original sources

High density of white-faced capuchins (Cebus capucinus) and habitat quality in the Taboga Forest of Costa Rica

Across the globe, primate species and habitats are threatened by human activity. This is especially true for species found in tropical dry forests, which are widely distributed and comprise diverse habitats that remain largely unprotected. Evidence suggests that some primate species endemic to tropical dry forests may be more sensitive to anthropogenic disturbance than others, but our ability to predict primate abundance in the face of disturbance also depends on the specific variables for each site. Here, we consider the factors that explain the high density of white-faced capuchins (Cebus capucinus) found in the Taboga Forest, Costa Rica, a relatively small fragment of tropical dry forest surrounded by agricultural fields. Our analyses suggest that, for capuchins (and potentially for mantled howler monkeys, Alouatta palliata), the size and disturbance of a forest fragment may matter less than the composition and availability of key resources, like above-ground water. Group sightings for both species were higher near permanent water sources, but group sightings did not vary between edge and interior forest. These findings help explain why some primate species can flourish even alongside anthropogenic disturbance and thus carry important implications for conservation efforts. Smaller forest fragments, like Taboga, may be able to support high densities of some species because they provide a mosaic of habitats and key resources that buffer adverse ecological conditions. Future studies will assess the extent to which primates in the Taboga Forest rely on the canals versus the river and will consider how the high density of capuchins in Taboga influences ranging patterns, home range overlap, and the frequency and intensity of intergroup encounters.\n\nRESEARCH HIGHLIGHTSO_LIHere we introduce a new white-faced capuchin study site in the Taboga Forest, Costa Rica, a fragmented tropical dry forest.\nC_LIO_LIForest fragments like Taboga may support high primate densities because they provide a mosaic of habitats and key resources.\nC_LI

animal behavior and cognition↗

The Goldilocks Effect: Female geladas in mid-sized groups have higher fitness

The cost-benefit ratio of group-living is thought to vary with group size: individuals in "optimally-sized" groups should have higher fitness than individuals in groups that are either too large or too small. However, the relationship between group size and individual fitness has been difficult to establish for long-lived species where the number of groups studied is typically quite low. Here we present evidence for optimal group size that maximizes female fitness in a population of geladas (Theropithecus gelada). Drawing on 14 years of demographic data, we found that females in small groups experienced the highest death rates, while females in mid-sized units exhibited the highest reproductive performance. This group-size effect on female reproductive performance was largely explained by variation in infant mortality (and, in particular, by infanticide from immigrant males) but not by variation in reproductive rates. Taken together, females in mid-sized units are projected to attain optimal fitness due to conspecific infanticide and, potentially, predation. Our findings provide insight into how and why group size shapes fitness in long-lived species.

evolutionary biology↗