Dr Kimberley Phillips, a primatologist at Trinity University in San Antonio, Texas has finally reached to a conclusion about an abnormal and odd behavior of Capuchin monkeys and a number of New World monkey species, including mantled howler monkeys and squirrel monkeys to urinate onto their hands then rub their urine over their bodies into their fur.
According to the latest research conducted by scientists, the brains of female tufted capuchins become more active when they smell the urine of sexually mature adult males. That suggests males wash with their urine to signal their availability and attractiveness to females.
While talking to BBC News, Dr. Phillips said,
“We reasoned that urine washing by males might provide chemical information to the females. But one study reported that when being solicited by female, adult males increased their rate of urine-washing. Since female capuchins [when they are most fertile] actively solicit males, we reasoned that urine washing by males might provide chemical information to the females about their sexual or social status,"