The bearded capuchin monkeys of northeastern Brazil eat a mostly plant-based diet, chowing down on palm nuts and other fruits. But when plant foods are scarce, the primates consume a surprisingly diverse smorgasbord of small animals, including snakes, opossums, iguanas, bats, rodents and bird eggs and nestlings, researchers report in a study published on August 26 in the journal PLOS One.

Hunting small prey seems to help capuchins cope with seasonal fluctuations in plant food availability—and "this may have also been the case for hominins," study co-author Susana Carvalho, a primatologist at Gorongosa National Park in Mozambique, tells Science News' Jake Buehler. The team recorded 446 instances of capuchins eating animals over 5,000 hours of observations at Fazenda Boa Vista between May 2006 and December 2010.

When their hunts were successful, the monkeys seemed to go for the brains and guts first, before eating the rest of the body. "This may allow them to obtain energy-rich fats and other nutrients quickly," says study co-author Noemi Spagnoletti, a conservation biologist at Sapienza University of Rome. Among primatologists, bearded capuchins are famous for using stone tools to obtain food.

The findings reveal new details about the diet and behavior of these highly adaptable, long-lived monkeys. But they could also shed light on the evolution of human diets, including our ancestors' shift toward eating more meat.