After observing Yaku Macaques and Sika Deer mingling on Yakushima, and subsequently doing some light research, I’m still having a hard time pinpointing what exactly this relationship is all about (#whatarewe?).

If I put on my science hat then I can say that the monkeys and deer have a symbiotic relationship because they live together. I can also say that it is likely mutualistic because they both have been reported to get something out of it. If I take my science hat off…I can describe their relationship as if each species had a profile on a dating app [science will be in brackets]. Disclaimer: until this was observed (yikes), scientists hadn’t reported mating going on… so the “dating” analogy is just for my enjoyment. There is not enough time in my day to get into that level of weirdness for this post (but feel free to go there on you own).

Interspecies Tinder

Species: Macaca fuscata yakui 

Nickname: Yaku Macaque

Hometown: Yakushima Island, Kagoshima Prefecture

About Yaku: Southern belle [southern most population of Japanese macaques] and not like other monkeys. Technically a Japanese macaque, but not that basic [because subspecies]. Prefers the island life to the flashy internet fame of its snow monkey relatives.

Likes: Lying in the middle of the road with friends and family. Taking long walks in the woods. When other monkeys play with its hair.  #GTL aka Groom-Travel-Lounge.

Dislikes: Direct eye contact

Favorite foods: Fruit, leaves, and seeds, but will be adventurous and eat the occasional bug or dirt clump [omnivore]. Terrible manners and drops food all over the ground. You can’t take this monkey to nice restaurants.

Social Life: Social butterfly [is actually monkey]. Always found with friends and family, but does not discriminate. Deer are monkeys too. Humans are whatever [habituated to humans but there is a personal bubble and if you cross it you will be destroyed].

Species: Cervus Nippon yakushimae

Nicknames: Yaku Sika, Sika Deer, Japanese Deer, Spotted Deer

Hometown: Yakushima Island, Kagoshima Prefecture

About Yaku Sika: Has anxiety [because deer], A little more petite than its mainland relatives [Subspecies of Sika deer]. Can be found both in the woods and on the road, looking for friends.

Likes: Giving monkeys rides in return for a lice check. 

Dislikes: Sudden movements.

Favorite foods: Plants, has been seen eating monkey poop but wont admit to it [herbivore]. Don’t judge, #reducereuserecycle? Is known to frequent the same food establishments as monkeys, even eavesdrops as monkeys discuss their meal plans and shows up at the same location. 

Basically is that coworker that shows up at your lunch spot uninvited.

Social life: Likes to hang out with other deer and also monkeys. Just wants to be included. Has a healthy distrust of humans due to their history of venison consumption.

In summary (in case my elaborate analogy only made sense to me, which is typical): Both the macaques and deer found on Yakushima are subspecies of their common relatives on mainland Japan. They are frequently found together on Yakushima, and researchers are still investigating why. It does seem clear that they each eat something found near, on, or that recently came out of, the other. As of late, there is evidence that things are getting a little frisky, but it seems uncommon.

I’m devastated that I didn’t get any magical photos of the monkeys directly interacting with the deer, or see it myself. Instead, I managed to only take photos of the monkeys and deer in which they look like they don’t want to be seen together and/or are annoyed by me. That was probably the inspiration behind this weird post that seemed like a good idea at the time. I hope you learned at least one thing.