Aotus griseimembra Elliot, 1912

Taxonomic History

The gray-handed night monkey (Aotus griseimembra) is a night monkey species from the family Aotidae that was formerly classified as a subspecies of the gray-bellied night monkey. Its exact taxonomic classification remains uncertain: some authors treat it as a subspecies of the gray-bellied night monkey (A. lemurinus), while others recognize it as a separate species, A. griseimembra.

General Distribution

It is native to parts of Colombia and Venezuela.

Colombian Range

In Colombia, its range covers the northern part of the country, extending from the Sinú River (or potentially further east) to the Venezuelan border. This range includes the Sierra Nevada de Santa Marta, as well as the valleys of the Magdalena River, Cauca River, and Sao Jorge River.

Venezuelan Range

In Venezuela, the gray-handed night monkey occurs west and south of Maracaibo.

Weight

It is a relatively small monkey: males weigh approximately 1009 grams (35.6 oz), while females weigh around 923 grams (32.6 oz).

Fur Texture

It has short, dense fur.

Body Fur Coloration

Its back fur ranges in color from grayish brown to reddish brown, and its belly is yellowish.

Distinguishing Limb Fur Feature

The hair on the backs of its hands and feet is light coffee-colored with darker tips, which is a key feature that distinguishes it from other subspecies of A. lemurinus.

Activity Pattern

The gray-handed night monkey is arboreal and nocturnal. It, along with all other members of the genus Aotus, belongs to the only group of nocturnal monkeys. Laboratory experiments have shown that the species has lower activity levels even when exposed to light levels matching a full moon.

Habitat Preferences

It can be found in multiple forest types, including secondary forest and coffee plantations, though one study noted it prefers highly diverse forests.

Group Size

It lives in small groups of 2 to 6 monkeys, most commonly 2 to 4 individuals.

Group Composition

Groups typically consist of an adult pair, one infant, and several juveniles and/or subadults.

Territoriality and Home Ranges

Groups are territorial, and their home ranges only overlap slightly.

Population Density

Different studies have recorded very different population densities: one found 1.5 monkeys per square kilometer, while another found 150 monkeys per square kilometer in a forest remnant that served as a refuge, which likely explains the extreme high density recorded there.

Mating System

Like other night monkeys, the gray-handed night monkey is one of the few monogamous monkey species.

Reproductive Output

Monogamous pairs usually produce a single infant each year, though twins are occasionally born.

Gestation Period

The gestation period lasts approximately 133 days.

Infant Care

The father carries the infant starting when the infant is one to two days old, only passing it to the mother for nursing.

Interbirth Interval

The average interbirth interval for mothers is 271 days.

Conservation Status

The International Union for Conservation of Nature (IUCN) lists the gray-handed night monkey as Vulnerable.

Threats

It is thought to be particularly threatened in Colombia, due in part to habitat loss, and also because many individuals were captured in the 1960s and 1970s for use in malaria research.