Doctoral Dissertation Research: Variation in Body Composition in Primates

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

Research on primate biological variation can be used in a comparative framework in human evolutionary studies and to provide excellent opportunities for student training and mentoring in STEM. This doctoral dissertation project examines primate body composition differences through non-invasive measures to better understand body shape, size and physiology.

The study advances knowledge about the relationship between physiological biomarkers and muscle mass and the development of sex differences in body composition, with the potential to inform research on human physiology and health. The findings from this study are disseminated through presentations at scientific conferences and publications in scientific journals, recommendations for zoo husbandry and primate conservation efforts, and outreach to the general public in popular science articles and zoo talks.

Undergraduate students, including individuals from groups traditionally underrepresented in STEM, are involved in the data collection, analysis, and dissemination efforts of the project.

Male bimaturism is an intriguing aspect of orangutan biology and there is still much that is unknown about the flanging process and the physiological differences between the two morphs. Flanged males weigh approximately twice as much as adult females and unflanged males, but it remains unclear if this weight gain results from increased bone, muscle, or fat mass, or a combination of the three.

This project analyzes creatinine and C-peptide of insulin levels in the three adult morphs of orangutans to assess relative levels of muscle and fat mass, respectively. It also utilizes body weights and testosterone levels in males to further assess these biomarkers of body composition. The investigators hypothesize that the body composition of the different sexes and morphs reflects their distinctive reproductive roles and social behaviors.

While both male morphs compete for mating opportunities with females, they use different strategies, which are suggested by their respective morphological and physiological traits. Thus, the investigators predict that flanged males are more muscular than either unflanged males or females, that female orangutans possess greater fat deposits than either male morph, and that males in particuar experience a decline in muscle mass associated with age.

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.