When scientists caught on video an Aye-aye using the eight centimeters of his eerily thin middle finger to pick his nose, they asked a bigger question: why do some animals eat their own boogers.
The Aye-aye, a small nocturnal lemur with large ears living in Madagascar, has become the 12th primate known to practice this kind of nasal exploration. He is there in noble company, with nothing less than the gorilla, the chimpanzee, the macaque, and of course the Man.
The researchers discovered the thing “by chance”, told AFP Anne-Claire Fabre, assistant professor at the Swiss University of Bern and first author of the study published this week in the journal Zoology.
She noticed the thing on the video of a female named Kali, filmed at the Duke Lemur Center, in North Carolina (United States), in 2015.
We see the animal “completely introduce its extra-long, thin and very mobile middle finger into its nasal septum before licking the collected mucus”, she explains.
All the species adept at the thing have to do this “fine manipulative capacities”, notes the researcher. The Aye-aye’s middle finger, apart from its length and thinness, has a single middle knuckle, which it uses to tap branches, looking for the larvae hiding inside.
The first thing the researcher wondered when watching the video was how far the animal was inserting its appendix.
To see it, the researcher who also has a job at the Natural History Museum in London, analyzed an Aye-aye skull with a scanner.
Before concluding that his finger probably reached his throat. “There is no other possibility. Otherwise it would be directly in the brain, and he would die of it,” says Ms. Fabre.
But as to why the Aye-aye, and some primates, eat their boogers is another matter altogether.
The researchers reviewed the scientific literature on the subject, which is content “for the most part to make it a subject of jokes”, according to her.
One study has suggested that this practice can spread bacteria in harmful ways. Another, on the other hand, concluded that the absorption of mucus could prevent the deposits of bacteria on the teeth.
So why is there so little research on the subject? “I think we didn’t try to find out more because we just found it disgusting,” says Ms. Fabre.
Which is surprising because there is a lot of research on coprophagia, which is ingesting one’s feces.
The Aye-aye, meanwhile, is a species in great danger of extinction, because it is perceived as an animal with a bad spell, according to the researcher.