Fission-Fusion Dynamics in Spider Monkeys in Belize
Abstract
Most diurnal primates live in cohesive social groups in which all or most members range in close proximity, but spider monkeys (Ateles) and chimpanzees (Pan) are known for their more fluid association patterns. These species have been traditionally described as living in fission-fusion societies, because they range in subgroups of frequently changing size and composition, in contrast with the more typical cohesive societies. In recent years the concept of fission-fusion dynamics has replaced the dichotomous fluid versus cohesive categorization, as it is now recognized that there is considerable variation in cohesiveness both within and between species. This thesis is a study of the fission-fusion dynamics in spider monkeys to quantify and explain temporal variation in subgroup size, spatial cohesion, and stability. I collected behavioural, ecological, and genetic data from a group of spider monkeys at Runaway Creek Nature Reserve in Belize from January 2008 until September 2013. I found that most subgroups were small (1-3 individuals), contained only adult females, and changed membership every 30-40 minutes. Habitat-wide fruit availability showed a weak relationship with subgroup size, contrary to what I expected, but it did explain some of the variation in subgroup stability. Likewise, degree of relatedness between individuals was not correlated with an association index that measured the likelihood that any two individuals would be in the same subgroup together. This thesis also describes the feeding ecology of the study group, and explores their genetic structure. The latter revealed some unexpected patterns: although traditionally believed to be a male philopatric, female dispersal species, male spider monkeys at Runaway Creek were no more closely related to one another than were females, and both males and females were residents and immigrants. As expected, given the common characterization of spider monkey males as experiencing low levels of within-group competition for females, paternity analysis revealed no reproductive skew, with all males siring offspring. Further analysis is needed to identify and understand the variables that are affecting the temporal changes in subgroup size, spatial cohesion, and stability of this group. However, this study makes an important contribution to this much larger question.
Description
Keywords
Anthropology, Ecology, Zoology
Citation
Hartwell, K. S. (2016). Fission-Fusion Dynamics in Spider Monkeys in Belize (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26183