Abstract # 247:

Scheduled for Saturday, June 20, 2015 01:00 PM-01:15 PM: (Cascade H) Oral Presentation


SPATIAL STRUCTURE WITHIN GELADA (THEROPITHECUS GELADA) ONE-MALE UNITS AT GUASSA, ETHIOPIA

S. Erskine1, P. Henzi1,2 and L. Barrett1,2
1University of Lethbridge , 4401 University Drive W, Lethbridge, Alberta T1K 3M4 , USA, 2Applied Behavioural Ecology and Ecosystems Research Group, UNISA, South Africa
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     This study aimed to identify some demographic and environmental factors related to spatial structure within foraging gelada (Theropithecus gelada) one-male units. High-precision GPS points were collected for each adult and subadult member of the unit during hour-long focal follows of each unit (9 units; 11–25 follows per unit; 4–9 adult/subadult animals per unit). Interpolation between GPS points yielded positions for all unit members at the same time. This study considered only times when a majority of unit members were foraging; 119 independent foraging times (>15 minutes apart) were obtained from 109 follows. Leader males were more towards the front of the group than adult or subadult females or follower males (p<=0.01 for all 3 comparisons). Adult females and leader males were more central than subadult females or followers (p<0.05 for all 4 comparisons). Foraging units were usually longer than they were wide; 75% of observations had the orientation of the unit’s longest axis within 36 degrees of the travel direction. Mean inter-individual distance (IID) at each time was analyzed using a linear mixed model with random effect of unit ID. IID was smaller in areas of higher vegetation index (NDVI calculated from Landsat8 imagery) and closer to the sleeping cliffs (slope=-0.528+- 0.175 for NDVI and 0.005+-0.001 for cliff distance, p=0.003 and p=0.002 respectively). Geladas forage farther apart when vegetation is sparser, perhaps to reduce competition.