South American Monkeys; wonderful and mysterious

Anyone who has stepped into a South American forest and become aware of monkeys peering quietly down or crashing in noisy gangs through the foliage will have felt their wonder. And yes, maybe mine is heightened by coming from a continent where there were never any native primates until the coming of people just some 50,000 years ago. I first encountered the thrill of wild monkeys in Africa (I'll never forget the moment in late afternoon in Windhoek, Namibia, looking down at a railway line and noticing the pack of dogs crossing the line - and suddenly realising they were baboons!), but since then I've seen many more, of species and individuals, in South America.

Male Grey Woolly Monkey Lagothrix cana, San Pedro area, Manu National Park, Peru.
(I confess to finding photography of dark animals in the canopy a challenge!)

The mystery is how they came to be there. Most extant South American mammals originated in North America, arriving in the last very few million years when the Isthmus of Panama arose and allowed two-way movement; all South American hoofed mammals and carnivores arrived this way. However there is no evidence of monkeys having ever existed in North America (unlike camels for instance, which arose there, dispersed, then became extinct in their homeland). Further, the fossil and genetic evidence points firmly to an origin of some 35 million years ago, when the two modern American continents were nowhere near each other.

Genetic evidence also makes it clear that South American monkeys (like the old South American rodents, such as guinea pigs, capybaras and viscachas) arose in Africa, so it seems that at a time when the Atlantic was narrower (though still most of 2000km across) a small band of unwilling monkey explorers made what must have been a horrific crossing on a raft of floating vegetation. (There was a highly controversial paper some four years ago which proposed that the monkey ancestors arose some 180 million years ago and were already in situ when the continents separated, but there is no fossil or genetic evidence to support this and it has already largely vanished from the discussion.)

Modern monkeys are divided most fundamentally into those who stayed at home in Africa (or made the more modest overland journey in increments to Asia), and those who crossed the Atlantic. Some of the key characteristics of the Old World monkeys - the catarrhines (from old Greek meaning 'hooked nose') - are narrow nostrils, close together and often down-pointing, and leathery buttock pads for sitting on.

Guereza Colobus Colobus guereza, Queen Elizabeth National Park, Uganda.
Especially if you click to expand the picture, you can see the characteristics of the catarrhine nose
on these two very beautiful animals.

Olive Baboon Papio anubis, Lake Mburo National Park, Uganda.
The useful callouses for sitting on are obvious.
(There is no suggestion that she had anything to do with the bottles before they were emptied!
As indeed didn't I...)

The South American platyrrhines - 'flat nosed' - have open and more widely spaced nostrils, no buttock pads, and most importantly, prehensile tails for grasping, which no Old World monkey has developed.

Ecuadorian Squirrel Monkey Saimiri macrodon, Yasuni National Park, Ecuador.
The platyrrhine nose features are evident.

Colombian (or Venezuelan) Red Howler Monkeys Alouatta seniculus at riverbank clay lick, Manu National Park, Peru,
nicely demonstrating the use of their prehensile tails.

There are five families of South American monkeys now generally recognised, and an interested visitor to the cloud forests and Amazon basin of the northern half of South America has an excellent chance of seeing examples of all five. The species numbers given are likely to increase in coming years, but after some big changes in our understanding in recent years things are starting to settle down again. Allow me to introduce the families, in increasing order of number of species.

* Aotidae, the night or owl monkeys, or douroucoulis, 10 species. These delightful little animals can sometimes be seen basking at the mouth of their communal tree hollow, and inspecting passing visitors. They emerge 15 minutes after sunset (there is virtually no twilight in the tropics) when daytime predators have retired for the day.

Spix's Night Monkeys Aotus vociferans, Yasuni National Park, Ecuador.
They typically live in social groups of up to five members.
Their huge eyes are an obvious adaptation to nocturnalism; while their ancestors had colour vision, typical of most primates, night monkeys have lost it.

* Callitrichidae, squirrel monkeys and capuchins, 16 species. Perhaps the monkeys most likely to be encountered; squirrel monkeys in particular move in noisy groups of up to a hundred, often low in the canopy and stopping to feed at fruiting trees. In such a group of squirrel monkeys, there will be perhaps 20 breeding females and a few breeding males; males play no part in caring for young, but the mothers get help from other females, especially her adult daughters. Capuchins, somewhat larger and less likely to hurl themselves into space, often accompany these foraging parties.

Ecuadorian Squirrel Monkey above, and
below with baby, Yasuni National Park, Ecuador.

 

Spix's White-fronted Capuchin Cebus unicolor, Yasuni National Park, Ecuador.
Taxonomy of capuchins is still hotly debated, and this one is also recognised as a sub-species.
Pretty much any plant matter or small animal, including tree frogs, is grist to capuchins' mill.
The name comes from a supposed resemblance to the garb of capuchin friars.

*Atelidae, spider, howler and woolly monkeys, 25 species. These are the 'typical' large South American monkeys, at least some of which are likely to be encountered.

The territorial roaring of howler monkeys is, to me, the sound of the Amazon, rolling over the forest by day or night, as the big males use an inflatable throat pouch and enlarged jaw bones to produce one of the loudest animal sounds known.

Colombian Red Howler Monkey, Manu National Park, Peru.
They have a large caecum and colon to assist with fermentation-digestion of a leafy diet.

Mantled Howler Monkey Allouata palliata, Manglares Churute Reserve Ecuador.
Here this species inhabits the highly threatened Pacific drier lowland forests.

Grey Woolly Monkey, Manu National Park, Peru.
As well as lowland rainforests, woollies can live higher in the cold cloud forests than do most other monkeys.

Black Spider Monkeys Ateles chamek at riverside clay lick, Manu National Park, Peru.
Sorry, the best I could do! Spider monkeys are characterised by very long slender limbs and tails for swinging along below the forest branches.

* Pitheciidae, uakaris, sakis and titi monkeys, 40 species. Despite being a large family, these monkeys are not so often encountered, at least in areas where I've visited. They tend to be high canopy fruit eaters; sakis, unusually among South American monkeys, do not have prehensile tails.

Monk Saki male Pithecia monachus, Yasuni National Park, Ecuador.
This big male was typically wary, despite being way above our heads. Much of the apparent bulk is actually fur.

Dusky Titi Monkey Callicebus moloch (but I think this one - the species, not this monkey! - has been split up),
Rio Madre de Dios, Peru.
Unlike most primates, titis apparently form long-term pair bonds. They feed quietly and closer to the ground than sakis.

* Callitrichidae, marmosets and tamarins, 41 species, including the smallest, and some of the most threatened South American monkeys. Some 20% of these species have been described in the last 20 years or so, and the number is rising. Groups of up to 20 of these tiny exquisite monkeys roam the canopies, gleaning almost anything they find. From the ground the view can be frustrating, but some will also come down near to our level, to provide some of our most precious memories of the continent.

Graell's Black-mantled Tamarin Saguinus graellsi, Sacha Lodge Rainforest Tower, Ecuador.
Now regarded as a separate species from the Black-mantled Tamarin from further east, this one can often be seen in the gardens of Sacha Lodge.

Golden-mantled Tamarin Saguinus tripartitus, Napo Lodge, Ecuador.
These glorious little animals are a feature of this Quichua community-owned lodge.

A longer than usual posting, but it's a big topic, and I hope as interesting to you as it is to me. No substitute for seeing them for yourself though of course!

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