Chimps have a taste for crabs

Chimpanzees have a taste for aquatic food, researchers have discovered.

A paper in the Journal of Human Evolution, written by Kathelijne Koops from the University of Zurich, and colleagues, documents year-round crab-catching behaviour by a troupe of chimps (Pan troglodytes verus) resident in the rainforest of the Nimba Mountains in Guinea, West Africa.

Film captured by the scientists clearly shows the apes painstakingly dredging through a muddy stream bed and lifting rocks at the water’s edge in pursuit of small freshwater crabs.

The behaviour, the researchers report, took place regardless of rainfall levels or season. The little crustaceans were not alternatives to foods such as ripe fruit, but an adjunct, and were favoured much more by females and juveniles than males. {%recommended 8363%}

The discovery not only increases knowledge of the diet of the chimpanzees themselves, but may also provide clues to how early hominins sourced their food.

“The aquatic fauna our ancestors consumed likely provided essential long-chain polyunsaturated fatty acids, required for optimal brain growth and function,” explains Koops.

“Further, our findings suggest that aquatic fauna may have been a regular part of hominins’ diets and not just a seasonal fallback food.”

This is certainly not the first case of primates being observed eating crabs – indeed, there is a species of monkey commonly known as the crab-eating macaque (Macaca fascicularis) but, says co-author Tetsuro Matsuzawa, the discovery is important for two reasons.

“It is the first evidence of apes other than humans doing so,” he says. 

“Notably, previous observations were from monkey species in locations consistent with aquatic faunivory — lakes, rivers, or coastlines — and not in closed rainforest.”

“It’s exciting to see a behavior like this that allows us to improve our understanding of what drove our ancestors to diversify their diet.”

A chimpanzee lifting up rocks and searching for freshwater crabs. Kyoto University/Kathelijne Koops