Exploring why female monkeys shout so much during sex, researchers have found that the shouts actually help their partners to ejaculate, Live Science reports. Researchers from the German Primate Center looked at Barbary macaques and found that males ejaculated 59% of the times their partner yelled, and only 2% of the time that they didn’t. Females yell during 86% of all sexual encounters.
Hollering also leads to the sex being more vigorous—the researchers counted pelvic thrusts and timed them with shouting occurrence, and found that shouting increased thrusting. As Barbary macaques are very promiscuous, sperm levels in the male can get low, and the shouting, which the females do when they are most fertile, is a way for them to raise their chances of conception.