Ecological determinants and arboreal feeding positional behaviors in Pan troglodytes, with implications for hominoid evolution

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Humans and apes have unique skeletal features that distinguish them from the rest of the animal kingdom and contribute to a high degree of locomotor versatility. The reason these features evolved is uncertain, however, they are thought to have helped the ancestors of apes and humans to search for food in trees. This project will examine ape locomotion in differing environments in the wild, including forests, woodlands and grasslands, and while feeding on a variety of foods, to determine the circumstances during which distinctive anatomical features are used while foraging. The findings of this study will help to determine why apes and humans evolved features such as an upright torso and mobile shoulders, arms and hands. This project will support the education of women and underrepresented groups at all levels of education - elementary through graduate school - through students' direct involvement in the creation of science education material. The outreach in this project creates cross-cultural connections and increases the quality of science education. Students in the U.S. and at the international research site will help create science education outreach materials and contribute research and conservation virtual content for a National Museum exhibit on ape and human evolution. Scientific findings will be shared through article publications in peer-reviewed journals and presentations at professional meetings. Hominoids are distinguished by an upright torso and versatile locomotion. It is hypothesized that such versatility evolved to feed on ripe fruit in the forest canopy, since that is what living apes tend to do. However, recent fossil discoveries show that the earliest apes to display advanced anatomical features, such as an upright torso, fed on leaves and fruit in a partially open environment. To determine how locomotor versatility relates to foraging behavior, the living ape with the broadest habitat preference, the chimpanzee, will be studied. The central question of this research is: How does variation in arboreal habitat structure, and variation in food type and location, correlate with arboreal positional behavior in woodland and forest chimpanzees? This question will be addressed using video capture and observational data on chimpanzee positional behavior in different habitats. Linear models will be employed on observational data to explore the relationship between positional modes and contextual variables. Kinematic data will be extracted from limb excursions in video footage and analyzed to determine if positional performance is correlated with ecological and individual variables, and whether excursions are greatest for those behaviors that rely on the advanced anatomical features of interest. Studying chimpanzee movement in multiple contexts and habitats will assist in predicting why hominoids evolved innovative positional behaviors and why early hominins transitioned to a less arboreal existence. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.