I usually try and avoid blogging about primates, because I’m really not all that into them. I find monkeys and the great apes pretty boring, and have never had an interest in learning about them. There are, however, some really interesting primates. These are mostly animals I’ve never heard of until I stumble across them on the internet or flip through my Encyclopedia of Mammals and see something with a funny name. Today’s animal is one of those, and it’s called the slow loris, and it is weird. They were originally described by Dean Worcester in 1891 as having ‘the face of a bear, the hands of a monkey, and moved like a sloth’.
There are actually at least eight species of slow loris, that live in Southeast Asia, from India to the Philippines and Indonesia. They are forest specialists, and spend most of their lives in trees. They have specially built hands and feet that help them grip onto branches. The thumb on their feet and hands sticks out at 180 degrees, creating a pincer-like grip for the loris. Their muscles are also specially designed, to give lorises extra strength when hanging on. The flexor muscle of the toes starts at the thigh bone, giving a lot of power to the loris’s grip. Finally, slow lorises can hold onto things for hours, thanks to a special capillary network that keeps blood flowing to the hands. Slow lorises are nocturnal, which is why they have such ridiculously large eyes. The eyes are also equipped with a special membrane called the tapetum lucidum, which reflects light to improve night vision. The tapetum lucidum is what makes dogs and cats look possessed when you take pictures of them in low light.
Slow lorises are just that… slow. They are very deliberate climbers, and don’t really rush doing anything. In fact, their basal metabolic rate is about the same as that of a sloth. A low metabolic rate is usually associated with animals that eat a diet low in nutrients, as you don’t need quite as many calories is your BMR is low. But the slow loris is different. It eats a high calorie diet, so its low BMR makes no sense. One possible explanation is that the slow loris eats a diet full of toxins and poisons, so its slow metabolic rate helps process these.
Because they are so slow, slow lorises need some form of protection from predators. Usually what they do when threatened is just freeze, and hope a predator doesn’t spot them. But they have another form of defence, and it is very unusual. Slow lorises have a special gland near their armpits that produce a toxic secretion. When the lorises lick this gland, the secretion mixes with saliva and becomes very unpalatable to predators. Lorises often lick their babies with this toxic secretion to keep them safe. The bite of lorises is also toxic, which is a trait unique to lorises among mammals.
So I have to admit that not all primates are boring. Who would have thought that such a bizarre creature existed in the world of primates? Not me!
Cover image By David Haring / Duke Lemur Center – email, CC BY-SA 3.0
Are there any FAST lorises out there?
Nope. Just slow ones and slender lorises.
This is not correct. In 1924, a Dutch expedition head by the lame Amsterdam professor Dr. Ludvig van der Fluffen did in fact record an encounter with a fast loris in Borneo, but unfortunately the doctor’s physical handicap made it impossible for them to catch it, so there is still some controversy.
As an aside, it is said that prehistoric giant sloths could outrun a race horse for brief periods. At that time, of course, race horses ran at approximately the speed of a fox terrier. And even today, a slow loris that falls out of a tree falls at about the same speed as a gibbon.