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Last modified: Thursday, September 8, 2011

Links between sexual signaling, immune-endocrine functions focus of NSF grant to IU anthropologist

Sept. 8, 2011

BLOOMINGTON, Ind. -- An Indiana University Bloomington anthropologist has been awarded $304,000 from the National Science Foundation to conduct the first-ever study into the interrelationship between functional immunity, endocrine status and sexual signaling in primates.

Rhesus macaques

Photo by Frans de Waal, Primate Info Net

Rhesus macaques at the Tulane National Primate Research Center will be used to better understand the relationships between sexual signals and functional measures of immune fitness.

Print-Quality Photo

IU Department of Anthropology Assistant Professor Michael Muehlenbein will study body condition, behavior, endocrine function and immune function of 300 adult male and female rhesus macaques at the Tulane National Primate Research Center in Louisiana in an effort to gather information about the relationship between sexual signaling and immune-endocrine interactions. Muehlenbein said the work is unique in that most research to date has been conducted with birds and new findings on sexual signaling and immunocompetence in primates could result in a better understanding of the roles of immunity in primate behavioral ecology.

"Animals utilize a variety of ornamentations or signals, including coloration, to attract the attention of potential mates. Ornament expression is related to immune status in a number of species, but the relationships between these sexual signals and functional measures of immune fitness have not yet been adequately evaluated in human or nonhuman primates," he said.

Other researchers have found that tail length in male pea fowl has been positively associated with cell-mediated immune function, and the size of the bib feathers under the beak of male house sparrows has been indirectly associated with bird health (bigger bibs for healthier sparrows). There are many examples in many species. But Muehlenbein will be the first to evaluate such relationships in primates. "We believe sex skin coloration is an honest indicator of robust immunocompetence, and that both coloration and immunocompetence are modulated in part by the functions of various hormones," Muehlenbein said.

The work will try to determine whether or not sex skin coloration is indicative of immunocompetence and endocrine function, how endocrine and immune status are related to one another, and how body condition and endocrine and immune status change across breeding seasons. The Muehlenbein lab at IU in past research (IU news release here ) has identified significant correlations between testosterone and immune measures in human and nonhuman primates; testosterone-mediated immunosuppression is one of the relationships the researchers will be looking for in the macaques.

"It may be that sexual coloration is a reliable indicator of pathogen resistance that is maintained through hormone interactions with the immune and reproductive systems," Muehlenbein said. "Alternatively, immunocompetence may just be related to overall body condition. The utilization of endocrine, immune and body condition measures will be useful in evaluating these and other aspects of primate life histories. Research to clarify immune-endocrine interactions in nonhuman primates will provide a valuable comparative and evolutionary perspective to selection in our own species."

Collaborators with Muehlenbein on the grant are Kate Baker, a behavioral biologist at Tulane National Primate Research Center and a research professor in the Tulane University Department of Psychology, and Gregory Demas, an associate professor in the IU Department of Biology who is also director of IU's Center for the Integrative Study of Animal Behavior.

For more information or to speak with Muehlenbein, please contact Steve Chaplin, University Communications, at 812-856-1896 or