If you read this blog regularly you know that I’m not a huge fan of primates. But something about the name night monkeys just strikes me as really interesting. I can’t quite figure out why, maybe because they sound a bit like creepy things that wait until the darkest depths of the night to attack you.

A (somewhat) cute family of night monkeys.
Image by Panamanian_Night_Monkeys.jpg: birdphotos.comderivative work: WolfmanSF, CC BY 3.0, via Wikimedia Commons

Fortunately that’s not really what night monkeys do. They are small monkeys, only weighing from 455 grams to 1255 grams. Still, I imagine a swarm of night monkeys could be pretty terrifying. They have dense fur that can range in colour from silver-grey to yellow or brown, depending on species. They have lighter coloured faces with black markings on their faces, and huge, scary-looking eyes.

These eyes play a key role in the biology of the night monkey. You see, night monkeys are the only primate that is truly nocturnal. The large eyes help capture as much light as possible, allowing these little monkeys to leap as much as 5m on moonlit nights. They also can’t see in colour, as colour vision is not very useful in the dark.

The exact number of extant species of night monkeys is still under debate, but there are at least eight recognized species. All species are found in South America, from Panama to northern Argentina. They are exclusively arboreal, meaning they spend all their time in trees. During the day night monkeys hide in tree cavities or in thick vines — basically anywhere that protects them from predators. After all, when you’re a tiny monkey in a jungle, there’s a lot of nasty things that want to eat you. That’s why night monkeys evolved to be nocturnal in the first place. Not only are they safe from predators at night, but they also avoid competition from bigger, nastier primates.

He’s a little cute.
Image by Charles James Sharp, CC BY-SA 4.0, via Wikimedia Commons

Another strategy to stay safe is to live in groups, which night monkeys do. They live in family groups entered around a monogamous mating pair and their offspring. Both sexes help care for offspring. The monkeys communicate via a number of different calls, with over 50 different types of vocalizations known. They possess a throat sac that inflates to increase the volume of their calls.

So maybe night monkeys aren’t all that scary (though those eyes still weird me out), but I still wouldn’t want to be ambushed by a group of them in the middle of the night in a forest. To be fair though, I wouldn’t want to be ambushed by anything in the middle of the night in a jungle.

Cover image by Gary L. Clark, CC BY-SA 4.0, via Wikimedia Commons, cropped to fit