Eulemur as a Primate Model for Oxytocin System Evolution & Function

Contemporary theories of oxytocin’s conserved social functions directly stem from work examining behavioral and hormonal differences between closely related rodent species. While translating these findings to humans has proven difficult, research on non-human primates may help to bridge this gap. For my NSF-funded postdoctoral research on oxytocin (SBE-1808803), I turned to a unique animal model: the Eulemur genus of Malagasy lemurs. These endangered primates serve as a powerful ‘natural experiment’ to identify biological mechanisms fundamental to pair-bonding, as species within Eulemur exhibit both monogamous and promiscuous mating systems—the only primate genus known to possess such variation. Our research group, composed of comparative neuroendocrinologists, anthropologists, and evolutionary biologists, is working on multiple fronts to investigate the use of Eulemur as a primate model for oxytocin’s social functions. In one study, we generated the first known ‘maps’ of central oxytocin receptor distributions in seven species of Eulemur to test the highly influential hypothesis that promiscuous and pair-bonding species should possess differing receptor distributions in brain nuclei linked to social affiliation. In fact, we find little evidence of a rodent-like ‘pair-bonding circuit’, instead observing a distribution of oxytocin receptors distinct from any rodent (or other primate) characterized to date (Grebe et al., 2021). In a second study, we conducted naturalistic experiments at the Duke Lemur Center to test how oxytocin functioning—assessed via experimental hormone receptor blockades—predicts lemurs’ behavioral responses to the introduction of potential mating competitors. Results are currently being analyzed for this latter study—stay tuned!