Female Spider Monkeys (Ateles geoffroyi) Cope with Anthropogenic Disturbance Through Fission–Fusion Dynamics

Abstract

Most primates live in habitats with some level of anthropogenic disturbance, and such disturbances have a larger impact on frugivorous primates that are more sensitive to ecological disruptions than folivores. Fecal glucocorticoid metabolites provide insight into how the external environment affects internal physiological state, and thus provide information on how anthropogenic pressures become embodied. Here, I examine how subgroup size and glucocorticoids vary with high and low fruit abundance, and how fruit abundance, subgroup size, and activity budget affect fecal glucocorticoid metabolites in female spider monkeys (Ateles geoffroyi) living in an anthropogenically disturbed habitat. I measured these variables via behavioral, ecological, and fecal sampling for 15 months in 17 female spider monkeys at El Zota Biological Field Station. Subgroup size was significantly larger during periods of high fruit abundance, but glucocorticoids did not differ between periods of low and high fruit abundance. Monthly fruit abundance predicted subgroup sizes significantly, but did not predict fecal glucocorticoid concentrations. Increased resting time and reproductive state predicted fecal glucocorticoid concentrations significantly, but travel and foraging time had no significant effect on glucocorticoid concentrations. Individual resting time over the study period correlated negatively with glucocorticoid concentrations. These results suggest that spider monkeys cope with variation in fruit abundance by adjusting subgroup size, and that these adjustments may mitigate environmental stress in this mildly seasonal environment. The large, relatively productive forest size at this site, and the availability of anthropogenic food sources, enable this population of spider monkeys to cope with human-induced habitat disturbance.

Grouping behavior of Sumatran orangutans (Pongo abelii) and Tapanuli orangutans (Pongo tapanuliensis) living in forest with low fruit abundance

“…For other individual‐based fission–fusion species, such as spider monkeys ( Ateles spp.) and chimpanzees ( Pan troglodytes ), multiple studies have documented a significant positive correlation between food abundance and distribution, and party size (Chapman, Wrangham, & Chapman, 1995; Rodrigues, 2017; Shimooka, 2003; Symington, 1988; Wittiger & Boesch, 2013). Fissioning into smaller groups during periods of low fruit availability may reduce travel costs imposed by scramble competition (Snaith & Chapman, 2007).…”

Long-Tailed Macaque Response to Deforestation in a Plasmodium knowlesi-Endemic Area

“…Changes in group size may be due to a fluid fission–fusion social structure, especially in response to resource stress and habitat disturbance reported in some primate species [e.g. Ateles geoffroyi (Rodrigues 2017); Varecia variegata (Holmes et al 2016)], although long-term data on this are scarce. After a severe forest fires in Kalimantan, macaques adjusted to low fruit and flower availability by relying on fallback foods (e.g.…”

Network analysis as a tool to understand social development in spider monkeys

“…These constraints result in frequent sex‐segregated ranging and association patterns, where males and females may have limited time in association (Hartwell et al, 2014; Rodrigues, 2014). Furthermore, subgroup size varies flexibly with food availability, as large subgroups converge at large patches, whereas smaller subgroups are optimal when resources are scarce (Chapman et al, 1995; Rodrigues, 2017; Symington, 1990). However, rather than constraining social behavior, captivity may intensify it.…”

“…Only a handful of primate species exhibit highly fluid fission–fusion dynamics, including humans, chimpanzees, and spider monkeys (Aureli et al, 2008; Chapman, Chapman, & Wrangham, 1995; Symington, 1990). Such fission–fusion dynamics allow spider monkeys to flexibly cope with social and ecological challenges (Chapman, 1990; Chapman et al, 1995; Rodrigues, 2017; Schaffner, Rebecchini, Ramos‐Fernandez, Vick, & Aureli, 2012; Symington, 1990). Fission–fusion is characterized by an ebb and flow of splitting into subgroups and reuniting, which is in stark contrast to cohesive societies (Aureli et al, 2008).…”