Affiliation:
1. Dartmouth College
2. University of California, Merced
3. National Primate Rsearch Center of Thailand
4. Durham
Abstract
Abstract
Few animal species have the cognitive faculties or prehensile abilities needed to eliminate costly tooth-damaging grit from food surfaces. Some populations of monkeys wash sandy foods when standing water is readily accessible, but this propensity varies within groups for reasons unknown. Spontaneous food-washing emerged recently in a group of long-tailed macaques (Macaca fascicularis) on Koram Island, Thailand, motivating us to explore the factors that drive individual variation. We measured the mineral and physical properties of contaminant sands and conducted a field experiment, eliciting 1,282 food-handling bouts by 42 monkeys. Our results verify two long-standing presumptions, that monkeys have a strong aversion to sand and that removing it is intentional. Reinforcing this point, monkeys clean foods beyond the point of diminishing returns, a suboptimal behaviour that varies with rank. Dominant monkeys abstain from washing, balancing the long-term benefits of mitigating tooth wear against immediate energetic requirements, an essential predictor of reproductive fitness.
Publisher
Research Square Platform LLC
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