Abstract # 199:

Scheduled for Sunday, September 18, 2011 08:00 AM-08:15 AM: Session 25 (Meeting Room 408) Oral Presentation


VARIATION IN MALE DOMINANCE RELATIONSHIPS IN TWO MULTIMALE GROUPS OF MANTLED HOWLERS (ALOUATTA PALLIATA) AT LA PACIFICA, COSTA RICA

L. C. Corewyn1, M. R. Clarke2 and K. E. Glander3
1University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA, 2University of Texas Health Science Center-Houston (retired), 3Duke University
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Limited available data report that dominance among males in multimale groups of mantled howlers (Alouatta palliata) ranges from weakly linear and tolerant, to strongly linear and agonistic. Dominance relationships are predicted to be more tolerant when intergroup competition is high to increase cooperative success in competitions against extragroup males, versus more agonistic when intragroup competition is high for access to females. To test this hypothesis, we collected 1771 hours of focal data from 12/2009 to 12/2010 on males living in two multimale groups of similar size, sex ratio, and habitats on Hacienda La Pacifica, Costa Rica (Group 2, 4 males; Group 12, 5 males with 2 emigrating during the study). Dominance hierarchies were based on dyadic agonistic interactions. While the hierarchy in G2 was strongly linear with a distinguishable alpha male, there was a tie between the two dominant males in G12, suggesting a co-dominant alpha relationship not previously reported in the A. palliata literature. Consistent with this result, mean hourly rates of agonistic interactions among males were higher in G2 (0.22) than in G12 (0.10), approaching significance (Mann Whitney; p=0.057). Intergroup encounter rates were significantly higher in G12 (0.043/hr) than in G2 (0.017/hr; chi-square, p=0.01). These results suggest that intragroup male dominance relationships in this population may be partly structured by the existing degree of intergroup competition.