Perhaps due to its reduced function in humans, researchers have rarely explored the use of scent in primate communication. Olfactory messages have the potential to transmit important species- and individual-specific information about the sender. It is critical to decode this message to better understand mammalian social interactions.
Using funding from the National Science Foundation, doctoral student T. L. Morelli will explore the use of scent-marking and the importance of the Major Histocompatibility Complex (MHC) in primate kin recognition using behavioral, genetic, chemical, and experimental techniques, focusing specifically on wild populations of endangered Milne-Edward's sifakas (Propithecus edwardsi). This research is part of a broader framework to determine how identity, including kinship, affects social interactions and to explore the importance of olfaction to primates.
This dissertation project has four objectives. First, Morelli will sequence major histocompatibility complex genes in a wild Propithecus edwardsi population to determine what role the MHC plays in lemur communication and life history. Evidence in other taxa indicates that MHC diversity is both critical in immune function and recognizable to conspecifics through olfactory signatures. Given that scent communication is integral to the life of a lemur, more data about the effect of MHC in prosimian social interactions are needed. She will then compare these results to olfactory fingerprints produced from gas chromatography-mass spectrometry to determine whether sifakas could use scent correlates of the MHC to gain inclusive fitness benefits through kin selection and increased offspring survival resulting from optimizing mate compatibility. Furthermore, she will conduct two-choice preference tests to reveal whether sifakas can use scent to discriminate kinship. Finally, data produced in this study will be used to assess heterozygosity levels at the MHC in a wild lemur population, thus providing an evolutionarily relevant measurement to calculate the health of an endangered species. If habitat destruction and population isolation are reducing MHC variability, this could affect viability both through reduced pathogen resistance and through disrupted behavioral processes, such as mate choice based on MHC type.
Sensory ecology of primates is an exciting and expanding field of study; little research has been conducted, particularly on olfaction. This project will have intellectual merit by testing hypotheses on sociality and mating systems. Whether or not the study reveals that odor is used as a cue in kin discrimination, results will reveal important information about what the scent mark is actually communicating. Moreover, this would be the first in-depth description of an olfactory cue for kin recognition in a non-human primate, a direct link from genes to physiology and behavior. The broader impacts of this project include engaging, teaching, and employing people from diverse backgrounds, including U.S. undergraduates, U.S. and international volunteers, Malagasy undergraduates and graduates, and local Malagasy experts, as well as culminating in a successful Ph.D. degree. In addition, this research will have important implications for conserving endangered Malagasy primates in the face of rapid habitat destruction, providing data that can be useful to conserving populations of an endangered primate, and aiding future management of both wild and captive primate populations.
