I’ve got a confession to make: monkeys give me the creeps.

One time I was in a toy shop and picked up what I thought was a cute cuddly leopard, but when I turned it around it had a plastic human baby face. That’s how I feel about monkeys: WRONG. But, as with the bugs, I need to soldier on, and at least the equatorial saki has a face like a well-loved teddy bear rather than a shrivelled homo sapiens.

It’s known as a New World monkey, and its ancestors may have migrated to South America via island hopping or, more amusingly, on rafts of vegetation. If true, that journey must have sucked, and may explain why it now lives as far off the ground as possible in the Peruvian rainforest canopy.

Although it lacks the prehensile tail of its African cousins, the equatorial saki is still incredibly agile in the trees, mainly thanks to its strong limbs. Have you ever hung vertically from a bar? Ever tried jumping upwards from that position? Well a saki can, and with great ease. While living so high up in the trees gives you access to tasty fruit, nuts, seeds and insects, it also puts you in the slashing line of raptors, such as our friend the harpy eagle. Having said this, this saki is so elusive and lives in such unfriendly areas of the forest, it’s hard to observe and so we’re not entirely sure which birds might have it on their menu. Regardless, any predator is usually met with posturing and a cacophony of calls from the boys.

We’ve been able to identify at least 3 distinct equatorial saki calls, and when a group of researchers conducted playback experiments, the males reacted more vigorously to the imagined intruder. This could explain another peculiarity in their behaviour.

Not the weird way they apparently grip a tree branch, that’s entirely my doing.

It was generally thought that sakis lived in small, monogamous family groups with a breeding pair and their young, but one group also allowed another adult male into the fold. The resident couple of seven years had two daughters, and despite some initial grumpiness, the father allowed this new male to integrate. And integrate he did, mainly by mating with one of the daughters.

This didn’t seem too scandalous, because the father then left with the new male, was seen with another female, and then they both came back again to ward off another male who was moving in on the mother and daughters. By the end, all three mature adults had split off into other territories with new mates, with the mother and daughters staying with the new third male.

If you managed to follow this tale of a seven-year-saki itch, it’s thought the additional male helped defend the territory (at least when the father was still bothered about his mate), and that’s why he was welcomed into the group. It also shows that sakis have a more fluid social dynamic than first thought. Or this family just did more swinging than others (fnar fnar).


Latin: Pithecia aequatorialis

What? A hefty grey treetop monkey

Where? Peru and Ecuador, although its range is hazy because it’s so secretive

How big? Its body is about 39-44 cm / 15-17 “, and its tail from 45-47 cm / 15-18 ”

Endangered? Currently “Least Concern”, although hunting and (surprise) deforestation are starting to take their toll. They’re also captured for the pet trade.

Probable motto: Despite my looks, only the trees get my “strong-arm tactics”.

They sound interesting. Do they need my help at all?

Well it’s a rainforest animal, so regardless of its specific situation, yes. These organisations are helping protect the Amazon:

Amazon Conservation


Rainforest Alliance

Just to prove I’m not fibbing

Bezerra, Bruna et a., 2017. “Pitheciid vocal communication; what can we say about what they are saying? Ethnobiology and Conservation 6:15. doi:10.15451/ec2017­09­6.15­1­18

De Luna, Anna Gabriela et al. 2010. “Predation and predation attempts on red titi monkeys (Callicebus discolor) and equatorial sakis (Pithecia aequatorialis) in Amazonian Ecuador“. Folia Primatologica 81:86-95.

Di Fiore, A. et al. 2007. “Adult male replacement in socially monogamous equatorial saki monkeys (Pithecia aequatorialis)“. Folia Primatologica  78(2):88-98.

Dunn, J. C. & Cristóbal-Azkarate, J. 2016. “New World monkeys“. Nature Education Knowledge 7(6):1

Equatorial Saki (Pithecia aequatorialis)”. No date. iNaturalist.org.

Marsh, Laura K. 2014. “A taxonomic revision of the saki monkeys, Pithecia Desmarest, 1804“. Neotropical Primates 21(1):1-165.

Pithecia aequatorialis“. No date. IUCN Red List of Threatened Species.

Porter, Amy M. et al. 2015. “A saki saga: dynamic and disruptive relationships among Pithecia aequatorialis in Ecuador“. Folia Primatologica 86:455-473.

Featured image credit:”Equatorial saki”, by Buster&Bubby