Sexual apartheid in spider monkeys

EWW, boys! A species of spider monkey lives in sexually segregated societies, apparently because males attack females if they spend too much time together. They are the first non-human primates known to systematically separate along gender lines. Geoffroy’s spider monkeys (Ateles geoffroyi) live in loose groups of a few dozen individuals. Kayla Hartwell of the University of Calgary, Canada, and colleagues tracked a group of 34 monkeys in the rainforests of Belize. They found that males and females lived separately, albeit in the same area, for 15 out of 23 months. Males foraged in groups, but females foraged with just their infants. Only when food was scarce did the sexes come together (International Journal of Primatology, doi.org/rsf). “Males and females have evolved to be so different that spending time together quickly becomes hostile,” says Hartwell. She says males are friendly to each other, even falling asleep hugging, but are aggressive towards females. Females may accept this because they need the males’ protection from other males who would kill their infants.