Photo/IllutrationA male proboscis monkey with its distinctive enlarged nose (Provided by Ikki Matsuda of Chubu University)

  • Photo/Illustraion

Size does matter for proboscis monkeys, as males with bigger noses attract more females to their harems, a Japanese team has found.

Researchers said male proboscis monkeys with bigger noses also have bigger bodies and testis, indicating that they evolved to show their physical strength and high fertility with the size of their nose to avoid unnecessary competition over females.

Male proboscis monkeys have distinctive enlarged noses. One male heads a harem of female monkeys and their young, and harems group together to form troops to defend themselves against predators.

The researchers at Kyoto University's Primate Research Institute and Chubu University observed 18 wild proboscis monkeys living in Borneo in Southeast Asia and other monkeys reared in zoos in Japan and abroad.

“Proboscis monkeys probably evolved to develop their noses into such a peculiar shape because they create a distinctive social structure by living in groups,” said Ikki Matsuda, an associate professor of primatology at Chubu University.

“We want to unravel the mystery of the evolution by studying their genome and hormones as well.”

The results of the study were published in the U.S. scientific journal Science Advances on Feb. 22.