For the first time, researchers have observed chimpanzees in Gabon vigorously smashing forest hinge-back tortoises against tree trunks to try and crack open their shells and extract meat out of them.

It was usually adult male chimps that were successful at cracking open tortoise shells. One female and two adolescents were seen trying too, but they were unsuccessful, following which an adult male finished the job, sharing the meat with them.

In an unexpected observation, a adult male chimp cracked open a tortoise, ate half of its meat, then stored the remainder in a tree fork. He came back for it the next day, suggesting that chimpanzees plan for the future.

Chimpanzees in Gabon’s Loango National Park have tortoises on their menu. For the first time, researchers have observed the great apes vigorously smashing forest hinge-back tortoises (Kinixys erosa) against tree trunks to try and crack open their shells and extract meat out of them. Sometimes, the chimps share the meat too, according to a study published in Scientific Reports.

“We have known for decades that chimpanzees feed on meat from a variety of animal species, but until now the consumption of reptiles has not been observed,” Tobias Deschner, a primatologist at the Max Planck Institute for Evolutionary Anthropology in Germany and co-author of the study, said in a statement.

Most members of the Rekambo community of chimpanzees (Pan troglodytes troglodytes) in Loango National Park have only recently become habituated to the presence of scientists in the park, allowing Deschner and his colleagues to follow them daily. Between 2016 and 2018, the researchers observed 10 different chimps successfully crack open tortoises 34 times. The chimps generally started out by repeatedly smashing the shell covering the tortoise’s underside against a hard surface like a tree trunk, then climbed into a tree to consume the meat.

“What is particularly interesting is that they use a percussive technique that they normally employ to open hard-shelled fruits to gain access to meat of an animal that is almost inaccessible for any other predator,” Deschner said.

It was usually the seven adult male chimps that were successful at cracking open tortoise shells. The remaining three chimps that the researchers observed — an adult female, an adolescent female and an adolescent male — also tried to smash open tortoise shells, but were unsuccessful. In these cases, though, an adult male finished the job, sharing the meat with them.

“Sometimes, younger animals or females were unable to crack open the tortoise on their own. They then regularly handed the tortoise over to a stronger male who cracked the tortoise’s shell open and shared the meat with all other individuals present,” Simone Pika, lead author of the study and a cognitive scientist at the University of Osnabrück, Germany, said in the statement.

One instance in particular surprised the researchers. An adult male, who was on his own and had smashed open a tortoise, ate half of the tortoise meat while sitting in a tree, then stored the remaining meat into a tree fork. He climbed down, built a nest in a tree about 100 meters (330 feet) away, slept overnight, then returned the next morning to retrieve the rest of the meat.

This, Pika said, suggests that chimpanzees plan for the future. “The ability to plan for a future need, such as for instance hunger, has so far only been shown in non-human animals in experimental and/or captive settings,” she said. “Many scholars still believe that future-oriented cognition is a uniquely human ability. Our findings thus suggest that even after decades of research, we have not yet grasped the full complexity of chimpanzees’ intelligence and flexibility.”

The researchers recorded all instances of tortoise predation during the dry season, when other food is also abundant. They say that it could be because forest hinge-back tortoises are known to be active during the dry season, and the chimps are probably more likely to find them as the reptiles move around on dry leaf litter.

Video of chimpanzee cracking open a tortoise shell courtesy of the Max Planck Institute for Evolutionary Anthropology.

Video of chimpanzees sharing tortoise meat by Harmonie Klein.

Citation:

Pika, S., Klein, H., Bunel, S., Baas, P., Théleste, E., & Deschner, T. (2019). Wild chimpanzees (Pan troglodytes troglodytes) exploit tortoises (Kinixys erosa) via percussive technology. Scientific Reports, 9(1), 7661.