In Darwin’s “The Descent of Man” he discussed the colorful faces and genitals of some monkeys and apes and wondered about the evolution and function of these stunning colors. Studies demonstrate that for some species of primates, colorful skin may be important for communication- signaling competitive ability, sexual receptivity, or mate quality.
My work focuses on the colorful skin of wild and captive primates. Recently, I focused on vervet monkeys because males have vivid blue scrota which researchers have suggested may be related to male aggression and female mate choice. Across Africa and the Caribbean, I collected digital photographs of hundreds of male vervet monkeys to better understand the geographic distribution of the colorful sexual skin of vervet monkeys.

Using digital imaging software, these photographic data allowed me to identify how color differs among males of different ages. Younger males have a dull, less vivid blue color than the more striking blue of older males. Males in southern Africa and Eastern Africa are much more vivid and colorful than males in Western Africa and the Caribbean.

We do not yet know the reason for the variation we see across age and geography. Unexpectedly, captive male monkeys tend to be paler than wild male monkeys, suggesting that there may be environmental effects that play a role in the development of sexual skin color in this species. Developing this project further, I am working with collaborators to explore the genetic basis for color variation as well as explore connections between color and parasites, hormones, and behavior.

Under the leadership and training of the International Vervet Genome/Phenome Research Group, I visited seven African countries. Collecting data for my project was part of a larger experience working with government offices, local people, and local collaborators. These experiences enhanced my interest in exploring the issues researchers and primates face such as a need for more education resources and training for habitat country professionals training to build capacity in both conservation and research.

In collaboration with two other primatologists, I am currently shifting focus toward developing a long-term field project in The Gambia to grow my behavioral and color research on monkeys while also expanding my teaching from American students to include West African students. This project will provide training and mentorship programs to local students and professionals working in wildlife management and research.

One of the best parts of my role as an Assistant Professor at American Public University is that my teaching travels with me to the field which is a unique and rewarding experience for an anthropologist on the go.

About the Researcher

Jennifer Cramer earned a B.S. in Biology and Anthropology from the University of Illinois at Urbana-Champaign, a M.A. in Anthropology from New Mexico State University, and a Ph.D. in Anthropology from the University of Wisconsin-Milwaukee. As an undergraduate research assistant in a neuroscience lab, she learned that she was best suited to working with bigger creatures. Trained in biological anthropology, Jennifer currently studies the reproductive ecology and behavior of free-ranging monkeys. Outside of the classroom she enjoys traveling for research and has spent time in Costa Rica, Puerto Rico, St. Kitts, South Africa, Botswana, Zambia, Ghana, The Gambia, and Ethiopia.