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Project Abstract

The aim of this study was to examine the relationships between ecology, demography and behavior in order to address the question of which factors most greatly influence the density in two populations of howler monkeys (Alouatta seniculus) occurring at different densities in different forest types at Yasuní, Ecuador. Attempting to narrow down and tease apart many of the closely related biological factors thought to affect primate density is important, because it may further our understanding of the process of behavioral adaptations and because it is a critical component in conservation endeavors. This study had three main goals: (1) to evaluate whether the predicted differences in the ecological variables occurred at the high density site; (2) to identify whether the predicted trends in demography with increasing population density proposed for other primates were present at the high density site, and (3) to test which ecological variables best predicted the observed patterns of Alouatta behavior in order to identify which aspects of forest ecology were playing the largest roles influencing Alouatta densities.

Out of eight variables examined, five aspects of forest ecology were supported to possibly contribute to higher howler monkey population density: (1) soil fertility, (2) phenological productivity, (3) resource quality: leaves higher in protein, (4) resource density of high quality leaves and (5) resource density of leaves lower in secondary compounds. No significant differences were found in the demographic patterns between sites. It is suggested this may be due to the formation of new groups only present at the high density site and lower female-female aggression at the low density site enabling larger than expected group sizes. Lastly, when predicted behavioral patterns for each of the supported ecological variables were compared to observed patterns of Alouatta behavior, it was found that both higher plant quality (higher protein and lower secondary compounds) and higher density of these resources were most greatly influencing differences in Alouatta density. Thus, resource quality (in addition to abundance) is a primary factor underlying differences in densities, supporting previous findings in folivorous Old World primates.

Waorani Community Project

One the most rewarding activities of Abigail’s field work was the Waorani Community Project. During 2004-2005 she worked closely with indigenous communities in Yasuní on aspects of sustainable hunting practices within the context of a changing environment. Abigail held monthly meetings with community members which were aimed at sharing information and promoting understanding of the on-going research projects in their area as well as introducing basic forest ecology and sustainable use concepts.

Go to the Photo Gallery to view images of some of these meetings, as well as wildlife and field photos.