New World Primates 8: Paging the wicked witch

Male White-faced Saki

On one of the islands in the central lake live a family of one of the most distinctive of South American primates, the White-faced Saki Pithecia pithecia.The local name for these monkeys sounds like they would be more at home in the Wizard of Oz – they are called flying monkeys because of their prodigious jumps (up to 10m have been recorded). In the wild they have a wide distribution through the rainforests of South America, so they are listed by the IUCN as of Least Concern. Most of its closest relatives are also in reasonably good shape, although one, the Buffy Saki Pithecia albicans, is listed as Vulnerable.


Sakis and their relatives belong to a group called the pitheciids, and they have an unusual dietary specialisation. Unlike fruit-eaters, they do not act as agents of seed dispersal, instead being predators on seeds as they feed mainly on seeds, nuts, and unripe fruit, with some foliage and a small amount of animal protein in addition.

Plants take steps against their vital reproductive resources being destroyed in this way, and protect themselves with both physical defences and chemical protection in the form of toxins in unripe fruit and seeds. The pitheciids however have developed means of circumventing these to gain access to a food source other animals cannot use. Some of these take the form of anatomical modifications of the jaws and teeth to enable them to break open the husks and seeds, but they also use self-medication to combat the effects of ingested poisons. This medication takes the form of geophagy – eating clays and minerals to neutralise poisons and speed their removal from the body. This behaviour is well known in parrots, especially macaws, as they too are seed predators and face the same chemical challenges from their diet. The observations of sakis performing this behaviour have been of them eating the walls of arboreal termite mounds rich in kaolin, which avoids them having to risk descending to the ground.

Sakis move around in small family groups comprising an adult pair plus up to four offspring of various ages. They defend their territories with calls, especially a duet of the adult pair, which sounds rather bird-like. Their most distinctive feature is the great difference in appearance between adult males and both females and juveniles. This kind of difference is often associated with a haremic social structure, but white-faced sakis are apparently monogamous. Although groups containing more than one adult male are known, it is likely that the extra males are in reality mature offspring of the breeding pair. Young male sakis start to develop their adult appearance at around 2-years, prior to leaving their birth groups and starting families of their own. In the wild the lifespan is probably up to 15 years, longer in captivity as they are not exposed to predators.

Female White-faced saki with young

Currently ISIS lists around 350 in zoos worldwide, and they have a reasonably good breeding record. As with most animals in zoos these days, they are managed via a studbook – in fact there are two, one for North American animals and another for Europe. Bristol manages the studbook for Europe, and our pair breeds regularly, so we have sent young to other zoos all over Europe.

Although the sakis are not especially endangered, some other pitheciids are in a much worse state. Unfortunately, these forms are even more specialised than the sakis, and in common with many such animals, providing proper food and accommodation in captivity may be difficult. In common with many animals that live in the canopy of primary rainforest, living in a confined space close to ground level is stressful, and although visitors to zoos will notice the floor space of an enclosure, people tend not to pay so much attention to the height of an enclosure. From those husbandry manuals I have read, many tend not to even specify enclosure height, which I feel is a potential omission from good practise. While many monkeys, especially smaller ones, live their lives with 10m of the ground, other species definitely prefer to be as high as possible. The same is true of many forest birds, which will often choose the highest nest site available if they have a chance.

One of the most distinctive of the white-faced sakis relatives is the Bald Uakari, Cacajao calvus, which is unfortunately currently listed as Vulnerable by the IUCN. This is a much larger and more social species, with some groups being over 30 strong, but it is confined to flooded forest areas. As with most rainforest animals, deforestation is the major threat, closely followed by hunting. Few Uakaris have been kept in captivity, and even more seldom bred, because of their specialisations. The only ones in North America are at LA zoo, but I am not sure if they are on show.

Bald Uakari

Next week, we reach the final chapter in this series – a group of monkeys which have developed a unique behaviour for a higher primate, they are nocturnal. This has been the cause of some confusion as to how many there are, as I will talk about next time.

(Images from wikipedia, animal planet website)