The world’s only poisonous primate

From the live-and-learn department, as discussed in today’s Guardian: the world has several venomous mammals (including shrews and the platypus), but there’s only one venomous primate. It’s the slow loris, which comprises three species (all from south or southeast Asia) in the genus Nycticebus.

Here’s a description of the situation from Dr. Brian Grieg Fry, who works on these creatures.

Unlike most primates, the lorises do not leap through trees. Rather they carefully and methodically move their feet in an almost chameleon-like manner, an impression greatly enhanced by thumbs that are more opposing than other primates. Specialised blood vessels allow them to grip on for hours. (This seems especially true when I’m trying to get some work done and Elvie will not let go of my hand and let me type!) When disturbed, (like trying to press return on my keyboard) lorises make a very unique low buzzing sound, much as if they were trying to play the digeridoo but without a didge or using their lips! True talent. In addition to this, when Lorises feel that battle stations is necessary, they fold their arms into a diamond around their head. While this looks incredible cute and useless as a defence mechanism, it allows for them to quickly take the toxin from their fore arms into their mouth in preparation for biting. This is reminiscent of karate moves at the last draw corral. Ah, I see you know the grasshopper, but do you know the Slow Loris?!

Having worked extensively with the lorises for the last couple years I am absolutely smitten with them. However, while they have the face of those cute and cuddly gremlins, they have the attitude of the evil, after-midnight flipside. With disproportionately huge and sharp canine teeth (very fang-like) and powerful jaw muscles their bites alone can be absolutely agonising. However, the pain is compounded by factors beyond the simple tissue trauma caused by the mechanical damage from the powerful jaws. The lorises are actually toxic! On the inside of their elbows, sebaceous tissue secretes a toxin (like sweat pores, which is rather fitting since the toxic mixture smells remarkably like sweaty socks). The lorises take it into their mouth and deliver it in the bite. It is not the upper and lower jaw vampire like canine teeth that deliver this toxin. It is the innocuously small teeth in the front of the lower jaw which slope forward and help conduct the saliva into the wound. One time I was working with the large lorises in the research collection and a visiting vet student from Belgium saw me putting on big thick gloves. She asked why I was doing that and I told her about the viciousness of the lorises. She looked at them and said that they couldn’t hurt anyone and besides, it wouldn’t be any fun to use gloves. I raised an eyebrow and said ‘be my guest’. Two hours later, with her hand still painfully throbbing merrily away despite the many ice packs on it, I asked her if she was having fun yet!

Of course this is an evolutionary puzzle, since if this is an adaptation, which it certainly appears to be, what were the intermediate evolutionary stages of the “poison patch,” and how were they adaptive? A paper in Naturwissenschaften suggests that the active protein in loris “venom” is an allergen, most similar to one seen in cats.

At any rate, slow lorises aren’t always mean.  Here’s one enjoying a good tickling.  Take that, P. Z.!!!

Thanks to Matthew Cobb for calling this to my attention. By the way, he’s just published a great new book on the French Resistance. Yes, it’s odd for a biologist to do this, but he’s a polymath.