Oh deer: Sexual interaction between animals of different species is an incredibly rare event in nature, but the attempts of snow monkey to mate with not one, but two Sika deer have been captured on camera.
The macaque monkey's antics on the Japanese island of Yakushima were recorded by researchers in 2015, and recently published in the journal Primates.
The journal claims the curious monkey is a low-status male among the troop, but asserted his dominance by guarding his favourite Sika deers - and chasing away other monkeys who came near.
The monkey's first attempt to mount a deer was met without resistance, but the second deer took exception to the monkey's behaviour and tried to shake the primate off her back.
Research leader Marie Pelé says the monkey was filmed during the mating season, and a hormonal surge likely prompted its sexual activity.
"It could be a manifestation of the known play behaviour between Japanese macaques and the deer they are known to sometimes ride".
Ms Pelé says the habits of the monkeys and deer overlap, with the deer benefitting from when monkeys shake down food from trees.
There are other examples of different species being observed having sexual behaviour.
In the 1990s, park rangers in South Africa noticed bull elephants attempting to mount rhino cows; while in 2008 a chimpanzee was filmed trying to mate with a frog.
Perhaps most infamously in 2006 a fur seal was recorded in sub-Antarctica attempting to copulate with a king penguin.
When the seal realised that things weren't going to plan it subsequently ate the penguin.