Chimpanzees gesture for (and bond over) food

Photo by Toshihiro Gamo/Flickr

Chimpanzees not only know how to point each other in the direction of sources of food, they also build closer relationships through the act of sharing food, according to two new studies published last week.

 

The first study, published in the journal Nature Communications, finds that chimpanzees are capable of making intentional gestures to help other chimpanzees locate hidden food. The study was conducted at Georgia State University's Language Research Center, which is home to four research chimpanzees. The center's research focuses on "comparative cognition studies: spatial memory, delay of gratification, numerical cognition, analogical reasoning, and cooperation."

 

In this new study, the researchers hid a piece of food in an outdoor enclosure. Two chimpanzees witnessed the act. The researchers then sent a human who didn't know where the food was hidden in with the chimpanzees. The primates were able to point out the location of the hidden food to the human. Not only that, the chimpanzees adapted the speed of their gestures when the human got closer to the food. In a press release, senior research scientist Charles Menzel called this the "chimpanzee-as-director" study and said it illustrates "the high level of intentionality chimpanzees are capable of, including their use of directional gestures. This study adds to our understanding of how well chimpanzees can remember and communicate about their environment." Fellow researcher Anna Roberts, from the University of Chester, said gestures are "an important building block in the evolution of language."

 

Meanwhile, the second study, published in Proceedings of the Royal Society B, found that the act of food sharing among chimpanzees is a bonding experience. The researchers, from the Max Planck Institute for Evolutionary Anthropology and other institutions, studied wild chimpanzees in Uganda during and after the relatively rare act of food sharing. The team studied the urine of the chimpanzees after they ate and found that the apes who shared their food had significantly higher levels of oxytocin, commonly known as the "love hormone," which is also typically released when mammals give birth and has been linked to maternal bonding.

 

In this case, the higher oxytocin levels weren't tied to familial bonds. The researchers found that any food-sharing experience increased the hormone levels. The well-known act of chimpanzee grooming also releases the hormone, but it does so in lower amounts than food sharing. As the researchers write in their paper, "food sharing in chimpanzees may play a key role in social bonding under the influence of oxytocin." Lead author Roman Wittig of the Max Planck Institute told the Associated Press, "We think food sharing can help spark new friendships, whereas grooming is more for confirmation of existing relationships."