Photographer captures monkey "enjoying a free ride" on the back of a deer in Japanese forest

A rare image of a monkey riding on a deer's back has gone viral after the U.K. Natural History Museum released it in a preview of its Wildlife Photographer of the Year competition. The photograph, shot by Atsuyuki Ohshima in a Japanese forest, captured the rare — but not unheard-of — interaction between a macaque and a deer.

Atsuyuki noticed a sudden movement of the deer, a sika stag, and then noticed a Yakushima macaque springing off a tree and onto the deer's back. 

Atsuyuki shared the photo, titled "Forest Rodeo," on Instagram, explaining in the caption that "male macaques have been seen clinging to female deer and trying to mate with them."