It's a dirty job, but I guess somebody's gotta do it...

Study Reveals Why Monkeys Shout During Sex:

To investigate the purpose behind these calls, scientists at the German Primate Center in Göttingen focused on Barbary macaques for two years in a nature reserve in Gibraltar.

The researchers found that females yelled during 86 percent of all sexual encounters. When females shouted, males ejaculated 59 percent of the time. However, when females did not holler, males ejaculated less than 2 percent of the time.

To see if yelling resulted from how vigorous the sex was, the scientists counted the number of pelvic thrusts males gave and timed when they happened. They found when shouting occurred, thrusting increased. In other words, hollering led to more vigorous sex.

Counting monkey pelvic thrusts is admittedly "quite weird, but it's science," researcher Dana Pfefferle, a behavioral scientist and primatologist at the German Primate Center, told LiveScience. "You get used to it."

I suppose the next step will be to try and figure out when they're faking.