Black squirrel monkey  (Saimiri vanzolinii)

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (4).

First described as recently as 1985, and still viewed by some as a regional subspecies rather than a full species (3) (5) (6), the black squirrel monkey has the most restricted range of its genus (7). Like other squirrel monkeys, it is a small, highly active monkey with short, thick fur and a long, non-prehensile tail. The head is rounded, with large eyes and large, whitish ears, and the small face bears a black, naked muzzle (2) (3) (8). Around the dark eyes is a mask of white fur, which is more rounded than in most other squirrel monkey species (9). The rest of the body is yellowish, paler on the underparts, and the tail has a black, slightly tufted tip (2) (3) (8). The black squirrel monkey has a relatively thin tail in comparison with other species, and gains its common name from the black band of fur running from the crown of the head to the tail (9).

Both male and female squirrel monkeys are similar in appearance, and infants resemble the adults (2) (5). However, the male is slightly larger than the female, and may increase in body weight prior to the breeding season, becoming noticeably fatter in the arms, chest and head (8) (9), although this has not yet been verified in this species (7). Squirrel monkeys are particularly vocal primates, using a variety of calls including chirps, peeps, squawks, purrs, barks and shrieks (2) (8).

The black squirrel monkey is found only in a small area of northwestern Brazil between the Solimões and Japurá Rivers (1) (2) (6) (10).

This species typically occurs in seasonally flooded forest, river edge forest, floodplain and secondary forest (1) (11). It is mainly found in the lower levels of the forest, but may also use the higher levels of the canopy, and sometimes also comes to the ground (1) (5) (8).

Although little is known about the biology of this species, it is likely to share much in common with other squirrel monkeys (6) (9). Most active during the day (2) (10), these small primates feed mainly on fruit and insects, supplemented with other small animal prey, birds’ eggs, nectar, flowers, and other plant parts (2) (5) (9). Movement through the trees is either by walking or running on all fours, or by leaping, with the long tail aiding balance (1) (5) (10) (12).

Squirrel monkeys form the largest groups of any New World primates (2) (5), with group size ranging from 20 to 50 or more and including individuals of both sexes and all ages (1) (10) (12). Unusually, groups appear to engage in relatively little social activity such as mutual grooming (5) (8). It is likely that, as in other species, the female black squirrel monkey gives birth to a single young (8) (10), probably in the rainy season (8), after a gestation period of around 145 to 172 days (2) (9). The newborn clings to the female for the first few weeks of life, becoming independent after about a year (2). Female squirrel monkeys reach sexual maturity at around 2.5 to 3 years, and males at 4 to 5 years (2) (5) (8). Lifespan in this genus may be up to 30 years in captivity (2).

Despite being heavily captured in the past for biomedical research and the pet market (2) (5) (12), most squirrel monkey species are still considered relatively abundant (2). However, the status of the black squirrel monkey is much less secure in light of its highly restricted range and potentially small population. Although the area in which it occurs is well managed and the species is not known to be hunted, habitat disturbance through selective logging may pose a threat (1) (2) (13). It has also been suggested that the common squirrel monkey, Saimiri sciureus, may be invading the black squirrel monkey’s range (6). Hybridisation between the species is a potential threat (1), but the two are not thought to interbreed (6), and the extent to which competition may be impacting the black squirrel monkey is not yet known.

The black squirrel monkey occurs entirely within the Mamirauá Sustainable Development Reserve (1) (6) (11) (13), a protected area with strong conservation programmes. The reserve is also a designated Ramsar site, considered a wetland of global importance (14). Although its restricted range means the black squirrel monkey is particularly vulnerable to declines, these and other conservation measures may go some way towards preventing this small primate from disappearing before it is even properly known.

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on primate conservation see:

IUCN/SSC Primate Specialist Group:
http://www.primate-sg.org/

To find out more about squirrel monkeys see:

Primate Info Net:
http://pin.primate.wisc.edu/factsheets/entry/squirrel_monkey