The 85th Annual Meeting of the American Association of Physical Anthropologists (2016)


Operational sex ratio, dominance rank and mating success of group and non-group male ring-tailed lemurs (Lemur catta)

AMBER D. WALKER-BOLTON1 and JOYCE A. PARGA2.

1Anthropology, University of Toronto, 2Anthropology, California State University, Los Angeles

April 14, 2016 1:30, A 602 Add to calendar

Sexual selection theory states that male mating success depends on intrinsic male qualities, but mating success can also be impacted by extrinsic factors. Male mating success is known to be impacted by the operational sex ratio (OSR) in several diverse species. We examined the relationship between OSR, dominance rank, and male mating success in four groups of ring-tailed lemur (Lemur catta) at Berenty Reserve Madagascar based on data collected in three mating seasons. We found significant relationships between the OSR during mating (calculated based on whether males were present and engaged in competition for the estrous female) and thrust duration (Mann–Whitney U = 0.0001, n0 = 4 < n1 = 11, P < 0.001 two-tailed), as well as OSR and female rank (R=-0.603, N=17, P=0.010). Incidence of ejaculation was shown to correlate with thrust duration (R=0.704, N=15 mating bouts, P=0.003). Alpha males copulated (thrusted) for longer durations than lower ranking group males (Mann–Whitney U = 0.0001, n0 = 5 > n1 = 4, P < 0.016 two-tailed). When non-alphas of the estrous female’s group were considered, extra group males were more likely to ejaculate than group males (R=0.828, N=11, P=0.002). These findings show that variation in the OSR during a female’s estrous period impacts male reproductive success as higher levels of male-male competition inhibit ejaculation and raise questions about the value of group membership for non-alpha males.

This research funded by University of Toronto School of Graduate Studies and Department of Anthropology, University of Toronto Scarborough Office of the Vice-President of Research, and an Ontario Graduate Scholarship.