Abstract # 127:

Scheduled for Sunday, September 18, 2011 10:45 AM-11:00 AM: Session 17 (Meeting Room 408) Oral Presentation


COLLECTIVE GROUP MOVEMENT AND LEADERSHIP IN BLACK HOWLER MONKEYS (ALOUATTA PIGRA)

S. Van Belle1, A. Estrada2 and P. A. Garber1
1University of Illinois, Urbana-Champaign, Department of Anthropology, Urbana, IL 61801, USA, 2Instituto de Biología, Universidad Nacional Autónoma de México
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Coordinating traveling time and direction and maintaining social cohesion is a primary benefit of group living in mammals. During a 10-month study, we investigated the behavioral factors underlying collective group movements in three multimale-multifemale groups of black howler monkeys (Alouatta pigra) at Palenque National Park, Mexico. A total of 344 travel bouts, defined as movement in which all group members traveled together for a distance of ? 25 m, were collected. Both adult males (N = 9) and females (N = 7) were observed to lead group movement, yet females initiated group movements significantly more frequently than males (X2(1) = 7.9, p = 0.005). The leading position was overtaken by another group member in 70 travel bouts, with males and females losing leadership during 26% and 16%, respectively, of their leading travel bouts. For 274 travel bouts in which leadership did not change, the sex of the leader had no influence on the distance traveled (U(1) = 838, P > 0.05), or the probability that the group would feed or rest upon arrival (X2(1) = 0.7, p > 0.05). However, travel bouts led by males, compare to those led by females, were significantly more frequently followed by howling (X2(1) =7.5, p = 0.015). The results suggest that black howler females play a more prominent role than adult males in initiating and directing group travel.