1Department of Anthropology, University of Texas at San Antonio, 2Department of Behavioral and Social Sciences, Houston Community College Southwest
Friday All day, Plaza Level
Mantled howler males at La Pacifica have been described as having an age-inverse dominance hierarchy. To elucidate this, an 11-month study was carried out on 2 multimale groups in 2010 (1792 H focal observations). Both groups inhabited upland habitat, and were similar in size and adult sex ratio. Group 2 (G2) has been documented as relatively stable over time, while capture records since 2000 indicate that membership in group 12 (G12) has been quite fluid. During this study, G2 had 4 males and no animals immigrated/emigrated, while G12 had 5 males, but 2 males and 2 females emigrated. Dominance hierarchies were determined from dyadic agonistic interactions. Male hierarchies were strongly linear (h1=1.0) with similar steepness scores (G2: Dij=0.690; G12: Dij=0.674). Close rank distance between the two highest ranking males in G12 suggested similar status. There was no relationship between age and rank in either group (G2: R2=0.226, p=0.525; G12: R2=0.407, p=0.247). While lacking specific historical observations, the 3 remaining males in G12 are close in age and currently appear cohesive. In G2, there is a documented secondary transfer who joined the group in 2004 at age 13, an older age than a “normal” primary transfer, and he soon attained alpha rank. If dates of achieving alpha rank in G2 are used instead of chronological age, there is a perfect reverse hierarchy based on date of “dominant achievement”, not age. In the absence of secondary transfers, dates of becoming dominant would correspond to age, and both would reflect an inverse hierarchy.
This research was supported by the Margot Marsh Biodiversity Foundation, and the Department of Anthropology and the International Education Fund at the University of Texas at San Antonio.