NEWS - Low-social monkeys wash their food in puddles to remove pebbles, while high-social monkeys eat the food with the sand attached. Non-dominant long-tailed macaques (Macaca fascicularis) diligently wash their teeth, while dominants are indifferent to dental health.
The researchers verified the disposable-soma hypothesis that monkeys have a strong aversion to sand and that removing it is a deliberate act. A choice to balance the long-term benefits of reducing tooth decay with immediate energy needs is an important predictor of reproductive fitness.
Few animal species have the cognitive abilities needed to remove pebbles from the surface of food that damages teeth. Some monkey populations wash food when puddles are easily accessible, but the tendency varies within groups for unknown reasons.
Jessica Rosien, an anthropologist at Dartmouth College in Hanover, and colleagues conducted a series of experiments in a colony of M. fascicularis inhabiting Koram Island, Thailand, to explore factors that drive individual variability in food handling behaviors associated with social rank.
They measured the mineral and physical properties of the contaminating sand and conducted field experiments on food handling by 42 monkeys. Monkeys have a strong aversion to sand and deliberately remove it.
Food cleaning behavior passes a point of diminishing returns, a suboptimal behavior that varies with social rank. Dominant monkeys do not wash their teeth, balancing the long-term benefits of preventing tooth decay with immediate energy needs.
The disposable-soma hypothesis predicts investment in immediate survival or reproductive needs rather than tooth preservation. Dominant monkeys face a predicament because rapid food intake is integral to maintaining dominance and achieving reproductive success.
Rosien and team found that dominant monkeys do not wash their food to maximize short-term energy intake. They prioritize immediate energy needs over the long-term benefits of their teeth, akin to a ‘live fast, die young’ strategy. This may explain why dominant males age more rapidly and die earlier.
Dominant monkeys do not wash at all, as if sacrificing their teeth for the high standing and social status that depend on rapid food intake. The researchers support the disposable-soma hypothesis for aging and test a valuable assumption in paleoanthropology.
These findings could impact views of the hominin fossil record by challenging the assumption that dietary variability is the primary cause of tooth wear. Paranthropus boisei had easy access to water which allowed them to diligently wash their food.
Paranthropus robustus has highly variable rates of tooth wear which may reflect the absence of extensive wetlands. Interestingly, the tooth wear observed in the Koshima Island apes closely matches the hominin fossil record.
Original research
Jessica E. Rosien, Luke D. Fannin, Justin D. Yeakel, Suchinda Malaivijitnond, Nathaniel J. Dominy, Amanda Tan (2024). Food-washing monkeys recognize the law of diminishing returns. eLife 13: RP98520. DOI:10.7554/eLife.98520.1
The researchers verified the disposable-soma hypothesis that monkeys have a strong aversion to sand and that removing it is a deliberate act. A choice to balance the long-term benefits of reducing tooth decay with immediate energy needs is an important predictor of reproductive fitness.
Few animal species have the cognitive abilities needed to remove pebbles from the surface of food that damages teeth. Some monkey populations wash food when puddles are easily accessible, but the tendency varies within groups for unknown reasons.
Jessica Rosien, an anthropologist at Dartmouth College in Hanover, and colleagues conducted a series of experiments in a colony of M. fascicularis inhabiting Koram Island, Thailand, to explore factors that drive individual variability in food handling behaviors associated with social rank.
They measured the mineral and physical properties of the contaminating sand and conducted field experiments on food handling by 42 monkeys. Monkeys have a strong aversion to sand and deliberately remove it.
Food cleaning behavior passes a point of diminishing returns, a suboptimal behavior that varies with social rank. Dominant monkeys do not wash their teeth, balancing the long-term benefits of preventing tooth decay with immediate energy needs.
The disposable-soma hypothesis predicts investment in immediate survival or reproductive needs rather than tooth preservation. Dominant monkeys face a predicament because rapid food intake is integral to maintaining dominance and achieving reproductive success.
Rosien and team found that dominant monkeys do not wash their food to maximize short-term energy intake. They prioritize immediate energy needs over the long-term benefits of their teeth, akin to a ‘live fast, die young’ strategy. This may explain why dominant males age more rapidly and die earlier.
Dominant monkeys do not wash at all, as if sacrificing their teeth for the high standing and social status that depend on rapid food intake. The researchers support the disposable-soma hypothesis for aging and test a valuable assumption in paleoanthropology.
These findings could impact views of the hominin fossil record by challenging the assumption that dietary variability is the primary cause of tooth wear. Paranthropus boisei had easy access to water which allowed them to diligently wash their food.
Paranthropus robustus has highly variable rates of tooth wear which may reflect the absence of extensive wetlands. Interestingly, the tooth wear observed in the Koshima Island apes closely matches the hominin fossil record.
Original research
Jessica E. Rosien, Luke D. Fannin, Justin D. Yeakel, Suchinda Malaivijitnond, Nathaniel J. Dominy, Amanda Tan (2024). Food-washing monkeys recognize the law of diminishing returns. eLife 13: RP98520. DOI:10.7554/eLife.98520.1