Monkeys Swap Grooming for Sex

What price for a little lovin'? Male macaque monkeys pay for sex by grooming females, but only as much as necessary: They groom for longer when fewer females are around, and for less time when there are more, according to a new study. "In primate societies, grooming is the underlying fabric of it all," said the doctor who ran the study.

Experts praised the work, but noted that males of other species often make a "mating effort" to win over females. "The interesting result" of the new study "is that the mating market seems to have an influence on the amount of this fee," one biology professor said. The study of 50 long-tailed macaques was conducted over a 20-month stretch in Central Kalimantan, Indonesia. (More sex stories.)