By Victoria Gill
Share and share alike: a male chimp will give up his hard-earned catch for sex
Chimpanzees enter into “deals” whereby they exchange meat for sex, according to researchers.
Male chimps that are willing to share the proceeds of their hunting expeditions mate twice as often as their more selfish counterparts.
This is a long-term exchange, so males continue to share their catch with females when they are not fertile, copulating with them when they are.
The team describe their findings in the journal PLoS One.
Cristina Gomes and her colleagues, from the Max Planck Institute for Evolutionary Anthropology in Germany, studied chimps in the Tai Forest reserve in Ivory Coast.
She and her team observed the animals as they hunted, and monitored the number of times they copulated.
“By sharing, the males increase the number of times they mate, and the females increase their intake of calories,” said Dr Gomes.
“What’s amazing is that if a male shares with a particular female, he doubles the number of times he copulates with her, which is likely to increase the probability of fertilising that female.”
High value
Meat is important for the animals’ diet because it is so high in protein. Since female chimps do not usually hunt, “they have a hard time getting it on their own,” explained Dr Gomes.
The “meat for sex hypothesis” had already been proposed to explain why male chimps might share with females.
But previous attempts to record the phenomenon failed, because researchers looked for direct exchanges, where a male shared meat with a fertile female and copulated with her right away.
Dr Gomes’ team took a new approach. In a previous study, she had found that grooming exchange – where the animals take it in turns to groom each other – happens over long periods, she related. “So we thought, why not meat and sex?
“We looked at chimps when they were not in oestrus, this means they don’t have sexual swellings and aren’t copulating.”
“The males still share with them – they might share meat with a female one day, and only copulate with her a day or two later.”
She suggests this study could lay the foundations for human studies exploring the link between “good hunting skills and reproductive success”.