Spider Monkeys Rule the Roost: Ateline Sleeping Sites Influence Rainforest Heterogeneity

Abstract

: The sleeping site behavior of Ateline primates has been of interest since the 1980s, yet limited focus has been given to their influence upon other rainforest species. Here, we use a combination of arboreal and terrestrial camera traps, and dung beetle pitfall traps, to characterize spider monkey sleeping site use and quantify the impact of their associated latrines on terrestrial vertebrate and dung beetle activity. We also characterize the physical characteristics of the sleeping sites and the floristic and soil composition of latrines beneath them. Spider monkey activity at sleeping sites peaked at dawn and dusk and group composition varied by sex of the adults detected. The habitat-use of terrestrial fauna (vertebrates and dung beetles) differed between latrine sites and non-latrine controls, underpinned by species-specific changes in the relative abundance of several seed-dispersing species (such as paca and great curassow). Seedling density was higher in latrines than in non-latrine controls. Although most soil properties were similar between latrines and controls, potassium and manganese concentrations were different. These results suggest that spider monkey sleeping site fidelity leads to a hotspot of ecological activity in latrines and downstream impacts on rainforest floristic composition and diversity.

Keywords: Ateline; biodiversity; camera traps; primates; rainforest; seed dispersal; seed predation; trophic interactions; wildlife.

Figure 1

Map of the study area. The Osa Biological Station is outlined in orange, and the 39 identified sleeping sites as part of the current study are represented by triangles; the 10 focal trees for investigation are represented by yellow triangles, all others by red. The inlay shows the location of the Osa Peninsula in the southwest pacific of Costa Rica, and the study location on the peninsula represented by the blue star.

Figure 2

Arboreal camera trapping summary. (A) Spider monkey sub-group made up of females and juveniles congregating in sleeping site; (B) male spider monkey showing aggressive behavior; (C) diel raw camera trap detections of spider monkeys in sleeping sites; (D) diel pattern in average group size.

Figure 3

The comparison of overall captures at non-latrine controls (“Con”) and latrines (“Lat”) for all vertebrate detections (A), mammal detections (B), and bird detections (C).

Figure 4

Non-metric multidimensional scaling (NMDS) plots of medium–large vertebrates (A), dung beetles (B), and soil parameters (C). Black circles = non-latrine controls; red triangles = latrines; x = species-specific loadings; grey polygon and dashed line = control community ellipse; red polygon and solid line = latrine community ellipse.

Figure 5

The differences in dung beetle species richness, abundance, and biomass at latrines and non-latrines; (A) dung beetle species richness per trap, (B) dung beetle abundance per trap, and (C) dung beetle biomass per trap (g); where “Con” = control sites and “Lat” = latrine sites.

Figure 6

(A) Seedling density by quadrat location. Where “Con” = control quadrat outside of tree crown; “Lat” = latrine location within tree crown; “Non-lat” = non-latrine location within tree crown. (B) Plant species richness vs. sleeping site use: Where points = latrine observed seedling species richness; black line = mean relationship between use and seedling richness; and grey shading = 95% confidence interval.