About Aotus vociferans (Spix, 1823)
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. It is a species of night monkey native to South America, where it is found in Brazil, Colombia, Ecuador, and Peru. This is a small-bodied monkey species with an average body mass around one kilogram and an average height of 0.5 meters. It belongs to Aotus, the only nocturnal genus of New World primates, and is classified as a New World monkey. Because its arms are longer than its legs, this monkey can leap farther than most other monkeys. The social behavior of Aotus vociferans centers on living in structured groups, which usually consist of a breeding pair and their offspring. This species has a monogamous mating system. After offspring are born, the father acts as the main caregiver, only giving the offspring to the mother to suckle. Offspring typically remain in their birth group until they reach two and a half to three and a half years of 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 is uncommon in this species. Aotus vociferans usually gives birth to a single offspring at a time, though twin births can occur, similar to humans. Females have an interbirth interval of around one year between births. Both mating and birthing take place between November and January. Copulation attempts in this species tend to be short and quick. The process begins when the male and female approach one another, and the male performs a social sniff. The female may or may not reciprocate the initial sniff. Sexual intercourse usually involves just three to four male thrusts, with the male ejaculating on the final thrust. 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. It communicates through four modalities: voice, sight, smell, and touch. Vocally, it produces different sounds for different situations. To startle potential predators, this night monkey will "scream", emitting a high-pitched shriek. The monkeys use social sniffing to assess potential breeding partners. They also urinate on their hands and rub the urine on different surfaces to signal sexual attraction. When acting aggressively, males usually arch their backs with all of their limbs straightened. When a predator is present, the night monkey will sway from side to side to attempt to deter the predator. 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.
