Video: Female Monkeys Throw Stones To Attract Males

To signal their readiness to mate and get males' attention, some female capuchin monkeys in a Brazilian forest reserve have taken to throwing stones at the objects of their desire. It's the first time this type of behavior has been witnessed in the wild. To make a scientifically dubious cross-species reference, perhaps they have simply run out of other courtship ideas, like human men honking horns in this Seinfeld bit (at 1:45).

More typically, females signal their readiness to mate by pulling pouting faces, whining loudly or touching males and running away. But some female bearded capuchin monkeys in Serra da Capivara National Park have taken this more assertive approach. As the BBC reports: 

Unlike other monkeys, female capuchins do not have any physical indicators to show when they are at their most fertile or "proceptive". Without brightly colored, swollen genitals or strong smelling odors or liquids to communicate, the capuchins display they are ready to mate through their behavior. 

The stone-throwing was observed first in a group of three female monkeys, toward the peak of their "proceptive" phase, and later in another three females. The authors of the study, published in November in the journal PLOS ONE, wrote that this shows that behavior has likely been learned and passed on. 

Often times the rocks didn't actually hit the males, but in two cases, males hit with rocks ended up mating with the stone-slinging females. Hey, whatever works.