Evolutionary Anthropology, Duke University
Friday 218, Plaza Level
In primate studies, daily travel distance (DTD) is often estimated in order to calculate energy expenditure or test foraging hypotheses. For arboreal, group-living species, the Center of Mass (CM) method is traditionally used to measure DTD; a point is marked at the group’s perceived center of mass at a set time interval or upon each move, and the distance between consecutive points is measured and summed. For groups taking multiple travel paths, this method creates a central path that can be shorter than the individual paths and/or traverse unused areas. To address these issues, I designed and tested the Multiple Travel Paths (MTP) method in three groups of Udzungwa red colobus monkeys (Procolobus gordonorum) each with 33-43 individuals; DTD is calculated by recording all travel paths taken by the group’s individuals, weighing each path’s distance based on its proportional use by the group, and summing the paths’ weighted distances. DTD was calculated using each method for a random sample of 30 days. (Full-day focal follows were conducted between April 2009 and March 2010). DTD was on average 132 meters (12.5%) shorter using the CM method (mean DTD: MTP = 1064 ± 335m; CM = 932 ± 303m), a significant finding (repeated measures ANOVA, df = 29, F = 59.3, p < 0.00001). Compared to the CM method, the MTP method provides consistently longer estimates of DTD that are more representative of the actual distance traveled by an entire group, providing greater accuracy for testing ecological and foraging models.
This research was partially funded by the Margot Marsh Biodiversity Foundation.