Night Monkey Profile
Human night vision is pretty rubbish when compared with many mammals like cats and dogs. That’s because, as diurnal primates, we’ve evolved to use vision to differentiate between ripe and unripe fruits, safe and toxic berries, lickable and lethal frogs, etc. We do this using advanced colour vision, which involves clusters of colour-receptive cells all over the light-receiving surface of our eyes.
As a result, there’s not as much room left for the cells that pick up low light, so, like all monkeys, we tend to bump our shins on the coffee table when the lights are off.
All monkeys, that is, except for night monkeys.
Night Monkey Facts Overview
| Habitat: | Tropical and subtropical forests |
| Location: | Panama, Colombia, Ecuador, Peru, Brazil, Paraguay, Argentina, Bolivia, Venezuela |
| Lifespan: | Up to 20 years in the wild |
| Size: | Up to 46cm (18 inches) long |
| Weight: | Up to 1.2kg (4.7 lb) |
| Colour: | Typically, brown or gray with variations among species |
| Diet: | Primarily frugivorous, supplemented with leaves and insects |
| Predators: | Large raptors and arboreal carnivores |
| Top Speed: | Nor reported |
| No. of Species: | 9 |
| Conservation Status: | Ranging from Endangered to Least Concern (IUCN) |
Night monkeys, also called Douroucouli, are a genus of simian primates unusual in their ability to thrive in the dark. While all the other monkeys are asleep, these cute little guys are out munching on all the fruits, and without the ability to see in colour, they do it all by smell.
Descended from diurnal monkeys, these animals share a lot of similarities with the nocturnal lemurs, though they have evolved these features independently.
While they’re highly adaptable, they’re still under threat from deforestation, and researchers are hurrying to figure out a way to help.
Interesting Night Monkey Facts
1. They’re New World Monkeys
Night monkeys comprise the family Aotidae, inside which there is only one genus remaining, Aotus. New research has broken down the members of this genus into nine recognised species, divided loosely into grey-necked and red-necked groups, for reasons that should immediately be apparent.
These nine species are likely to gain or lose a few, as more gripping debate ensues over which are subspecies and which are true species, and for this genus, research is a little behind, on account t of the night monkeys being so busy at night.
Evolutionarily, it’s likely the ancestors of this family were once diurnal. At some point around 160 million years ago, the ancestors of lemurs went one way and the ancestors of monkeys went the other, and the former has many nocturnal species.
But evidence suggests that night monkeys began as a standard monkey, diverging from its African ancestors 40 million years later, and somehow being pressured into living in the dark. And these monkeys are the best at that. 1
2. They can do things other monkeys can’t
Being active at night removes you from a wealth of diurnal predator menus. Very few birds hunt at night, and even the predatory felines aren’t so hot in the deep dark of the cloud forest at midnight.
Also, once all your competitors have gone to bed you can happily exploit your favourite resources without bother. But, eyesight is a pretty useful thing to have, and in the blackness of the night, not being able to see is certainly a disadvantage for both predator avoidance and resource exploitation, so these monkeys have had to adapt.
3. They have excellent senses
Perhaps counter-intuitively, night monkeys rely heavily on vision. Their eyes are highly specialised for low light, giving up the space on their retina that would once have held colour-receptive and high-light processing cells, in favour of many more rod cells, able to function much better in the dark.
This means that while they can only see in shades of grey, they can see in fantastic resolution.
But vision isn’t the only sense that’s well-tuned. They have a powerful olfactory sense and are particularly good at hearing things. This might also be somewhat of a surprise, as they don’t have any ears. 2
4. They are “earless” monkeys
The genus Aotus translates to “One without ears”, and this is a reference to their lack of anything on the side of their heads you’d be able to put an earring on.
It’s not entirely accurate, of course; night monkeys do have ears, but they don’t have much of the external dangly bits we normally call ears. In fact, there are some small lobes there if you look very closely, but the fluffiness of the fur around these monkeys’ heads shrouds it.
In place of ears, they have enormous brown eyes: all the better for seeing you with. And this makes them look a lot more like the non-simian nocturnal primates. These eyes are what lend night monkeys the nickname “Owl monkeys”.
5. Sneeze grunting
This is very much a ‘dad’ behaviour, and one that night monkeys are well known for.
These little simians have quite a range of vocalisations, and each has its own meaning. Researchers have identified at least six distinct calls, one of which is a general alarm call called a sneeze-grunt. It’s used to make the family aware of non-specific threats, and make sure everyone’s on alert.
Other calls include a moan, a long scream, a gulp, a low trill, and a short scream, in cases where there isn’t time for a long scream. 3
6. Many are in trouble
Of the nine species of night monkey, six are in trouble, including the very endangered Andean night monkey.
As with all New World monkeys, they face threats from humans that disregard day or night. Habitat loss from the rampant deforestation in South America is something no native animal can evade and is the most serious threat to wildlife on the continent.
The pet trade is also a killer of monkeys, and these cute little primates are popular in illegal collections. As with many species here, the race is on to learn how to help them before it’s too late. 4
7. Researchers burn their tails
One of the most basic forms of research underpins almost everything researchers have to do to help a species. Identification and tracking of individuals is key to learning about them and with Night Monkeys, that’s done with a combination of Ketamine and freeze-branding.
This sounds pretty rough, and it is indeed a heavy-handed approach, but of all the options for catching an animal this elusive and agile, it’s proven to be one of the safest. Local hunters aid researchers in finding the monkeys, and a blow dart full of one of the most popular party drugs of the ‘90s is employed to great effect.
The monkey, thoroughly tripping balls, drops safely into a net and the tail is touched with dry ice to give the animal an identifying mark.
A collar is attached, and the monkey is left to return to Earth, nursing its comedown gently, but otherwise no worse for wear. This method has resulted in no deaths or life-threatening injuries and helps researchers figure out who’s who and learn about how these incredible animals live.
The use of this practice does make you wonder what kind of alien abduction legends that owl monkey society will be left with after an experience like that. 5
Night Monkey Fact-File Summary
Scientific Classification
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Family: | Aotidae |
| Genus: | Aotus |
Fact Sources & References
- (2010), “New theory on the origin of primates”, Science Daily.
- “PANAMANIAN NIGHT MONKEY”, New England Primate Conservacy.
- Author Name (Year), “Owl monkey”, Wisconsin Natural .
- “Andean Night Monkey”, IUCN Red List.
- (2003), “Field Methods for Capturing and Marking Azarai Night Monkeys”, Springer Link.