Doctoral Dissertation Improvement Grant: Effects of Hormonal and Social Factors on Primate Behavior

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Under the direction of Dr. Leanne Nash, Ms. Stephanie Meredith will collect data for her doctoral dissertation. A great deal of research has demonstrated that the development of sex differences in primate behavior depends on complex interactions between individual's external social environments and their internal physiological states (particularly the hormones governed by the hypothalamic-pituitary-gonadal axis). However, understanding of the relative importance of particular aspects of the social environment and specific components of individual physiology for the development of particular sex-typed behaviors is murky. This is especially true for behaviors which begin their sexual differentiation in the juvenile period. Furthermore, because almost all research in this area has been done on captive animals, it is especially unclear how social and physiological factors interact in natural environments to shape behavioral outcomes. As a result, very little is known about the evolution of social and physiological systems that produce adaptive sex-differences in behavior. This project will investigate the influence of social interaction and the steroid hormones testosterone and estradiol on sex-typed social development from birth through sexual maturity in a wild population of ring-tailed lemurs (Lemur catta) at Beza Mahafaly Special Reserve in Madagascar. Ring-tailed lemurs represent a compelling model system for study of social and physiological influences on primate sex-typed behavioral development because while they are similar to the better-studied captive monkeys in many aspects of social organization, they are strikingly different from most other primates in exhibiting female dominance over males. This combination of similarities and differences will maximize the ability to sort out the relative importance of "nature," "nurture," and their interaction for the development of a large number of behavioral traits and will indicate productive future research directions. This project will be the first to generate physiological data for developing Lemur catt. For the particular ring-tailed lemurs in this study, this work will be useful in interpreting their developmental biology and eventual lifetime reproductive success. These data, coupled with those derived from captive settings, will help to contextualize the results of developmental research in captivity. In addition, when compared to similar data from other primates, these data will help to pinpoint the biological and social underpinnings of complex, sex-typed behaviors across the primate order, and, ultimately, to clarify the evolution of primate sex-typed behavior.Beyond its contributions to scientific knowledge, this project will train developing scientists and will expand the skill set of and increase available research avenues for a female Ph.D candidate. This award also has major conservation implications, both present and future. Results from this award will provide behavioral and hormonal benchmarks useful for Beza Mahafaly Special Reserve management and for assessing the impact of habitat degradation on juvenile Lemur catta elsewhere. Because scientific research is a substantial and stabilizing economic force at Beza Mahafaly Special Reserve in protecting its endangered fauna, enhancing the potential for future research in Madagascar is an important positive impact.