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2018 Abstracts

The Space Between Us: Intraspecific Proximities of Alouatta palliata and Ateles geoffroyi

Ellison Goodrich, Salt Lake Community College

Alouatta palliata (the mantled howler monkey) and Ateles geoffroyi (the black handed spider monkey) are both found in the rainforests of Central and South America. The two species can coexist because they have different dietary needs, A. palliata relies on leaves (foliverous), which are abundant, while A. geoffroyi eats fruits and roots (frugivorous) which are less abundant and more patchily distributed. This difference in diet reduces competition between the species for resources. A. palliata will often form closed multimale-multifemale groups, with up to 40 individuals, and spend most of their day eating or sleeping. A. geoffroyi will typically spend their days traveling, foraging, resting, or engaged in social activities. A. geoffroyi typically lives in multimale-multifemale groups, and form a fission-fusion group structure, this means that their groups are more fluid and change often. This makes A. geoffroyi less territorial and eliminates competition for resources. Both species have an obvious male dominance hierarchy, but there is a difference in the activity pattern of the two species, with A. palliata being less active than A geoffroyi. Due to the social structures of both species, I hypothesize that I will see more affiliative behaviors in both species, than I will aggressive/agnostic. Due to the limited feeding competition in the folivorous A. palliata, I predict that the A. palliata will maintain closer intraspecific proximities than the A. geoffroyi. Data were collected at the La Selva Biological Station in Sarapiquí, Costa Rica, From May 11th to May 22nd, 2017. I conducted instantaneous scan samples in five-minute increments. At each interval, I recorded their behavior and their proximity to the nearest individual. The behaviors were divided into agnostic (fight/grab, bite, and grunt/growl) and affiliative (foraging, playing, rest, traveling, and grooming), and proximities were estimated in meters. It was found that A. geoffroyi and A. palliata showed higher rates of affiliative behaviors than they did aggressive, only 1% of recorded behaviors were agnostic supporting my hypothesis. It was also found that A. palliata maintained an overall proximity of 3.45 meters and A. geoffroyi 4.2 meters. A. palliata who relies on the abundance of leaves, experienced less feeding competition, and maintained closer proximities, supporting the hypothesis. A. geoffroyi experiences greater competition due to less abundance of food, which was reflected in the farther proximities in A. palliata, which also supports the hypothesis.