Sciency Thoughts: Number of Saki Monkey species raised from five to sixteen.

Saki Monkeys of the genus Pithecia are found throughout the tropical forests of South America. The taxonomy of the group is poorly understood, as species are often both variable and similar to other species and hard to observe in the wild, favouring old growth and often flooded forests. Many species were described in the nineteenth and early twentieth century by taxonomists working in European museums, with little or no information on where the specimens were collected, and only a limited understanding of the life histories of the living animals.

Female Saki Monkeys tend to be slightly smaller than males, but not to a great enough extent that this feature can be used to determine sex. More reliable is colouration, with adult males of most species having a distinctive coat that separates them from the females. However only fully adult males have this coat, with sub-adults resembling females, then going through an intermediate phase as they develop their male colouration, which can be mistaken for a completely different species. Since it can be hard to determine the sex of living Saki Monkeys by physical examination, this presented a considerable obstacle to nineteenth century taxonomists working from preserved specimens of unknown or inaccurately recorded origin (many early collectors in South America simply bought specimens from local hunters in large towns without worrying about where they came from; some may have lied about the origin of their specimens when selling them on to museums in order to increase their value).

The behaviour of the Monkeys does little to help this situation. They tend to live in dense and inaccessible forests, and for the most part will avoid contact with humans. They live in small family groups, often with subadult females as well as younger offspring, and when threatened the adult female will often sit on a conspicuous branch with an older juvenile female to observe the threat, while younger members of the group hide and the male circles round shaking vegetation to create a diversion. Thus observations of ‘pairs’ of Saki Monkeys are typically of an adult and subadult female.

Like most primate groups, Saki Monkeys are quite well studied today, but largely by ecologists rather than taxonomists. Ecologists for the most part have little taste for taxonomy, which tends to involve the extensive study of dead specimens in museums. However understanding the taxonomy of a group is vitally important for long-term conservation, as it is impossible to accurately determine population sizes or distribution if it is not possible to determine whether populations belong to the same or different species.

The last major review of the taxonomy of Saki Monkeys was carried out in 1987, when Phillip Hershkovitz of the Field Museum of Natural History in Chicago split the genus into five species and several subspecies (expand).

In a paper published in the journal Neotropical Primates in July 2014, Laura Marsh of the Global Conservation Institute in Santa Fe, New Mexico, undertakes a complete review of the genus Pithecia, concluding that there are in fact sixteen species. In doing this she reinstates three previously described species, promotes three subspecies to full species level, and erects five new species.

The White-faced Saki, Pithecia pithecia, was first described in 1766 by Swedish naturalist Carlus Linnaeus (under the name Simia pithecia, Saki Monkeys were not placed in a separate genus till 1804). The name has remained in use till today, though museum specimens have been described as a number of other species, and other species have been described as Pithecia pithecia. Adult male White-faced Sakis are more-or-less completely black, with white ‘half-moon’ facial disks. Females are brownish or greyish and may have white striping, and have orange chest hair, the colour of which varies in intensity in different populations. White-faced Sakis are found in Venezuela, Guyana, French Guiana, and Suriname, and in the Brazilian states of Roraima, Amapá and Pará.

The White-faced Saki, Pithecia pithecia. Marsh (2014).

The Golden-faced Saki, Pithecia chrysocephala, was first described in 1850 by Geoffroy Saint-Hilaire of the Museum d’Histoire Naturelle in Paris, but has been considered to be a subspecies of either Pithecia pithecia or Pithecia monacha for most of the last century. March re-elevates this group to full species level. Golden-faced Sakis resemble White-faced Sakis, but the face plates of the males are deep orange or reddish brown in colour. The Golden-faced Saki is found only in Brazil north of the Amazon.

The Golden-faced Saki, Pithecia chrysocephala. Marsh (2014).

The Hairy Saki, Pithecia hirsuta, was first described in 1823 by Johann Baptist von Spix of the Zoologische Staatssammlung in Munich, with the name remaining in use till today. This species shows little colour variation between the sexes, with both being black with some white stripping and some brown on the chest. The species is found in Brazil, Peru and Columbia between the Río Napoin and Rio Solimões in the south, the Río Caquetá and Rio Japurá in the north and Rio Negro to the east.

The Hairy Saki, Pithecia hirsuta. Marsh (2014).

Miller’s Saki, Pithecia milleri, was first described by Joel Allen of the American Museum of Natural History in 1914, but was reclassified as a subspecies of Pithecia monachus by Hershkovitz in 1987. Marsh re-elevates this taxon to full species status. Miller’s Saki resembles the Hairy Saki, but is more grizzled (greyer). The females are more distinctive in this species, being paler and shaggier than the males. Miller’s Saki is found in southwest Columbia and northeast Ecuador, and may also be present in neighbouring areas of Peru, though it has not been reported there.

Miller’s Saki, Pithecia milleri. Marsh (2014).

The Monk Saki, Pithecia monachus, was first described by Geoffroy Saint-Hilaire in 1812, and has been accepted as a valid species ever since, though several other species have been treated as members of this species at times. Males of this species tend to be black, with a little white stippling, mostly on the forearms and chest, and brown hair on the face. Females are more grizzled than the males, with brown hair only on the forehead. The species is found in eastern Peru and western Brazil.

The Monk Saki, Pithecia monachus. Marsh (2014).

The Burnished Saki, Pithecia inusta, was first described in 1824 by Johann Baptist von Spix, but was thought to be a population of Pithecia monachus by Hershkovitz in 1987. Marsh re-elevates this to full species status. Males are black with lighter stippling, the ruff is brown, with lighter brown hair tips, and can be buff or almost orange in older individuals. The face is an off-white colour. Females are similar to males, but with more white in their coats.

The Burnished Saki, Pithecia inusta. Marsh (2014).

Cazuza’s Saki, Pithecia cazuzai, is a new species erected by Marsh, to describe three populations formerly assigned to the species Pithecia irrorata (Grey’s Bald Faced Saki). It is named in honour of the Brazilian primatologist José de Sousa e Silva-Júnior, (known as ‘Cazuza’), of the Museu Paraense Emílio Goeldi, for his contribution to South American taxonomy. Both sexes are black with white grizzling, the females being darker and less grizzled than the males. The species is known only from Brazil around the Rio Juruá.

Cazuza’s Saki, Pithecia cazuzai. Marsh (2014).

The Equatorial Saki, Pithecia aequatorialis, was first described by Philip Hershkovitz in 1987. The males are black, with grizzled white tips to their hairs, a horseshoe-shaped white band around the face and an orange ruff. Females are greyer and more grizzled, with a less pronounced ruff. The species is found in Peru, south of the Río Napo and Río Curaray and west of the Río Tigre.

The Equatorial Saki, Pithecia aequatorialis. Marsh (2014).

The Napo Saki, Pithecia napensis, was first described by Einar Lönnberg of the Swedish Museum of Natural History as a subspecies of Pithecia monachus, though Hershkovitz did not accept that this was a valid taxon at all. Marsh re-introduces it, and elevates it to full species. Males are black, with grizzled white tips to their hair, a distinctive whit crown on the head and a white facial disk surrounding the face, fading to grey towards the bottom. The ruff is rusty or even bright orange. Females are greyer, with a brown ruff. The species is found in northeast Ecuador and northern Peru.

The Napo Saki, Pithecia napensis. Marsh (2014).

Isobel’s Saki, Pithecia isabela, is a new species erected by Marsh to describe several populations of Saki Monkeys in northern Peru, formerly assigned to the species Pithecia monachus but now recognized as distinct. Pithecia isabela is named in honour of Isabel Grameson Godin des Odonais, who mounted an expedition into the forests of French Guyana in search of her lost husband in 1768. The males have black coats, often with a coppery sheen, and a dark rusty-orange ruff. The face is black, and surrounded by a ring of light brown hair in younger males, though as they get older it darkens to black. The facial disk is dark, but lighter grizzling which makes it appear grey or even white; there are also white patches above the eyes. Females are similar to males, with a black coat with a coppery sheen, though on females this is heavily grizzled. The hair of the ruff is black with brown tips and the facial disk black.

Isobel’s Saki, Pithecia isobela. Marsh (2014).

The Buffy Saki, Pithecia albicans, was first described as a species by John Edward Gray of the British Museum of Natural History (now the Natural History Museum) in 1860, and has been recognized as a valid species ever since. This is a very distinctive species, larger than other members of the genus and covered in blond or orange fur, except for the back and tail, which are black. This species is found only in Brazil, between the lower Rio Purus and Rio Tefé and the Rio Solimões-Amazonas in Amazonas State.

The Buffy Saki, Pithecia albicans. Marsh (2014).

Gray’s Bald Faced Saki, Pithecia irrorata, was first described by species by John Edward Gray of the British Museum of Natural History (now the Natural History Museum) in 1842, and has been recognized as a valid species ever since. These Sakis are black with heavily grizzling that makes them appear grey or even whitish all over. The males have a white band or crown above the face, which is hairless and pink. This species is known from Peru and Brazil, though the known populations are somewhat scattered, and its full distribution is probably not known.

Gray’s Bald Faced Saki, Pithica irrorata. Marsh (2014).

Vanzolini’s Bald Faced Saki, Pithecia vanzolinii, was first described by Philip Hershkovitz in 1987. These are black or dark grey on their backs and tails, with cream or yellowish bellies and limbs. The males have a thicker coat than the females. This species is known only from southwest Brazil.

Vanzolini’s Bald Faced Saki, Pithica vanzolinii. Marsh (2014).

Mittermeier’s Tapajós Saki, Pithecia mittermeieri, is a new species named by Marsh in honour of Russell Mittermeier, President of Conservation International and long-time Chairman of the International Union for the Conservation of Nature Species Survival Commission’s Primate Specialist Group. The species comprises populations found south of the Rio Amazonas between the Rio Madeira and Rio Tapajós in Brazil, which were formerly assigned to Pithecia irrorata. These have black coats, but heavily grizzled with white hair, making them appear almost white, males have black faces and both sexes tend to get darker as they get older.

Mittermeier’s Tapajós Saki, Pithecia mittermeieri. Marsh (2014).

Ryland’s Bald-faced Saki, Pithecia rylandsi, is a new species named by Marsh in honour of Anthony Rylands, Senior Research Scientist at Conservation International, Deputy Chair of the International Union for the Conservation of Nature Species Survival Commission’s Primate Specialist Group, a member of the Brazilian Academy of Sciences, former professor of Vertebrate Zoology at the Federal University of Minas Gerais, and founding editor for the journal Neotropical Primates. The species comprises populations of Sakis from southern Peru, northwest Bolivia and southwest Brazil, which have formerly been assigned to several other species. These have black coats heavily grizzled with white, but turn completely white as they age. The faces are black in both sexes.

Ryland’s Bald-faced Saki, Pithecia rylandsi. Marsh (2014).

Pissinatti’s Bald-faced Saki, Pithecia pissinattii, is a new species named by Marsh in honour of Alcides Pissinatti, a Brazilian veterinarian, director and co-founder of the Centro de Primatologia do Rio de Janeiro as well as Vice President of the Brazilian Academy of Veterinary Sciences, for his work on captive breeding programs of Saki Monkeys. The species comprises populations in Brazil previously assigned to Pithecia irrorata and Pithecia hirsuta. These are very grizzled Sakis with bare faces, the males become brownish with age.