Filippo Aureli []

Universidad Veracruzana, Mexico and Liverpool John Moores University, UK

Colleen M. Schaffner []

Universidad Veracruzana, Mexico (formerly at University of Chester, UK) 

Our long-term project in Santa Rosa started in 2000 and is the second longest continuous project on any spider monkey species (the longest being ours in Yucatan, Mexico). It has involved several PhD students, postdocs and volunteers, and it counts on the invaluable assistance of Elvin Murillo Chacon. The project originally focused on the social and ecological factors affecting the social organization of spider monkeys (Ateles geoffroyi) but it has expanded to cover diverse issues from behavioral traditions to color vision, from geophagy to forest quality. With the long-term dataset we continue to address open theoretical and empirical issues and provide information relevant to conservation initiatives. Below are a few highlights about our findings. 

  • Spider monkeys live in communities with a high degree of fission-fusion dynamics (Aureli et al. 2008:;uid=2134&uid=2&uid=70&uid=4&sid=21101332762511), in which members are rarely all together, fissioning and fusing in subgroups of variable membership. We demonstrated that fisssion-fusion dynamics are a means to deal with food scarcity as spider monkeys adjust subgroup size to local resource availability to reduce aggressive competition (Asensio et al. 2008: and not to increase travel costs (Asensio et al. 2009:

  • Using GPS data of the location of each visible community member within a circle with 100-meter radius at given intervals we were able to obtain a quantitative definition of subgroup and confirm the definition we have intuitively used in the field (Aureli et al. 2012:

  • GPS data have also been used to determine the study group’s home range and core area (i.e. the area of intense use within a home range). We demonstrated that spider monkeys’ core areas contain higher quality habitat than non-core areas, supporting the concept of core areas including the most critical resources for an animal population (Asensio et al. 2012a: We also found that core areas change over time within a stable home range (Asensio et al. 2012b: This is conceptually important for territorial species, such as spider monkeys, which defend a stable home range as it contains not only the current, but also the future core areas.

  • A cross-site comparison identified and documented the existence of traditions both in the display of unusual behavioral variants (Santorelli et al. 2011a: and the relative use of common behaviors (Santorelli et al. 2011b: Such findings provide evidence for within-species behavioral variation, a neglected component of biodiversity.

  • In collaboration with colleagues at the University of Tokyo and the University of Calgary, we are investigating genetic and behavioral aspects of color vision polymorphism. Contrary to the predicted advantage of trichromacy, we did not find differences in foraging efficiency between dichromatic and trichromatic monkeys, and luminance contrast was the main determinant of the variation of foraging efficiency (Hiramatsu et al. 2008: In addition, monkeys use olfaction for discrimination between edible and inedible fruits when vision alone is insufficient to evaluate the quality of fruits (Hiramatsu et al. 2009:

  • We witnessed the first ever reported cases of group take-over by males in a spider monkey population. The males in this species are thought not to disperse from their natal group, so the events are remarkable. Our ability to document these rare events is probably due to the long-term nature of our study and the individual recognition of monkeys over extended period of time.

  • We documented unusual feeding habits of spider monkeys. In certain periods of the year, they chew off and eat pieces of soft rock from a cliff face, and this behavior seems to be associated with feeding on Phoradendron mature leaves, which are potentially toxic. We started an in-depth project to investigate the potential relation between geophagy and eating Phoradendron leaves, and results are expected shortly.