Aotus vociferans (Spix, 1823)

Common and Scientific Names

Spix's night monkey, with the scientific name Aotus vociferans (Spix, 1823), is also commonly called the Colombian gray night monkey, noisy night monkey, and Spix's owl monkey.

Geographic Distribution

It is a species of night monkey native to South America, where it is found in Brazil, Colombia, Ecuador, and Peru.

Size and Physical Measurements

This is a small-bodied monkey species with an average body mass around one kilogram and an average height of 0.5 meters.

Taxonomic Classification

It belongs to Aotus, the only nocturnal genus of New World primates, and is classified as a New World monkey.

Locomotor Adaptation

Because its arms are longer than its legs, this monkey can leap farther than most other monkeys.

Social Group Structure

The social behavior of Aotus vociferans centers on living in structured groups, which usually consist of a breeding pair and their offspring.

Mating System

This species has a monogamous mating system.

Parental Care Roles

After offspring are born, the father acts as the main caregiver, only giving the offspring to the mother to suckle.

Offspring Dispersal Age

Offspring typically remain in their birth group until they reach two and a half to three and a half years of age.

Exception to Dispersal Age

An exception occurs if the breeding male is no longer present, most often due to death; in this case, offspring may leave their birth group between twelve weeks old and the normal departure age.

Social Grooming Behavior

Social grooming is uncommon in this species.

Litter Size

Aotus vociferans usually gives birth to a single offspring at a time, though twin births can occur, similar to humans.

Female Reproductive Interval

Females have an interbirth interval of around one year between births.

Mating and Birthing Season

Both mating and birthing take place between November and January.

Copulation Duration

Copulation attempts in this species tend to be short and quick.

Copulation Initiation

The process begins when the male and female approach one another, and the male performs a social sniff.

Female Response to Initial Sniff

The female may or may not reciprocate the initial sniff.

Copulation Mechanics

Sexual intercourse usually involves just three to four male thrusts, with the male ejaculating on the final thrust.

Arboreal Locomotion Methods

This species moves through the forest by swinging between horizontal branches, using all four limbs to grip branches.

It may also leap from tree to tree.

Communication Modalities

It communicates through four modalities: voice, sight, smell, and touch.

Vocal Communication Overview

Vocally, it produces different sounds for different situations.

Predator Startle Vocalization

To startle potential predators, this night monkey will "scream", emitting a high-pitched shriek.

Olfactory Mating Assessment

The monkeys use social sniffing to assess potential breeding partners.

Scent Marking for Sexual Signaling

They also urinate on their hands and rub the urine on different surfaces to signal sexual attraction.

Male Aggressive Display

When acting aggressively, males usually arch their backs with all of their limbs straightened.

Predator Deterrence Behavior

When a predator is present, the night monkey will sway from side to side to attempt to deter the predator.

Tactile Rejection Communication

A rejection bite is used as tactile communication: between mother and offspring after suckling, or when the offspring is around one week old and contact is not welcome; between father and offspring when the offspring reaches around 8 weeks old and contact is not welcome.