1Animal Ecology and Conservation, University of Hamburg, 2Nocturnal Primate Research Group, Department of Social Sciences, Oxford Brookes University
April 16, 2016 , Atrium Ballroom A/B
The proximate and ultimate determinants that may have prompted the shift from an arboreal to terrestrial feeding niche, whether due to environmental change, seasonality, and/or predation pressure, are poorly understood. Within a fragmented littoral forest in southeast Madagascar, a strepsirrhine population of the typically arboreal genus Hapalemur spends a large proportion of time on the ground. We therefore aim to identify the costs and benefits imposed on feeding terrestrially by an arboreal primate. From January to December 2013, we observed three social groups of southern bamboo lemurs H. meridionalis for 1,762 h, recording continuous feeding time on all food items separated by strata (arboreal or terrestrial), and biochemical analyses on each item for dietary quality comparisons. Considering only full-day focal follows (n=106), our model predicted increased terrestrial feeding by both seasonal factors (cooler temperature and decreased precipitation) as well as metabolizable energy in the diet, but not by protein/fiber ratio or by canopy exposure. Despite the lack of difference in canopy exposure between the two feeding strata, however, focal subjects fed more closely to a conspecific when on the ground, suggesting increased vigilance. Our study provides empirical evidence for an ultimate origin of terrestriality, suggesting a seasonal alternative to increasing metabolizable energy intake. Coupled with the disturbance of the habitat, our results suggest that the initial expansion to a terrestrial dietary niche occurred when the nutritional pay-off was greater in the new strata and predation risk was even (or less) compared to the original arboreal stratum.
American Society of Primatologists, Conservation International’s Primate Action Fund, IdeaWild, Mohamed bin Zayed Species Conservation Fund (Project Number: 11253008), Primate Conservation Inc., and Primate Society of Great Britain/Knowsley Safari Park.