Geographic Range
Aotus nigriceps
(black-headed night monkey) is native to neotropical South America. Black-headed
night monkeys are found in an area roughly within the boundaries of 5 to 15° south
latitude and 75 to 55° west longitude. This area includes the Amazonian and Madeiran
forests in Peru, Brazil, and Columbia and several forest areas found in the Huallaga,
Ucayali, Yavari, Purus, and Madre de Dios river basins. It encompasses those areas
south of the Amazon River to the Madeira River Basin and the northwestern part of
the Tapajoz River Basin. Black-headed night monkeys are a species of "red-necked"
or "southern" night monkeys.
- Biogeographic Regions
- neotropical
Habitat
Black-headed night monkeys are usually found in lowland and hillside tropical forest
areas. They are usually found in the higher canopy levels of the forest. They choose
exclusive sleeping sites in the crooks of branches, especially in trees in the genus
Miconia
. These trees have large leaves and relatively thick canopy cover.
Aotus
species generally do not modify their sleeping environments. Other night monkey species,
A.vociferans
and
A. nancymae
, have been observed co-occupying sleeping sites with
Potos flavus
,
Bassaricyon gabbi
,
Coendu bicolor
,
Tamandua tridactyla
,
Isothrix bistriatus
and
bat
species.
- Habitat Regions
- tropical
- terrestrial
- Terrestrial Biomes
- forest
- rainforest
Physical Description
Black-headed night monkeys are small primates approximately the same size as a small
squirrel. While there are few data concerning the mass of
A. nigriceps
specifically,
Aotus
species, both male and female, average 750 g as adults, reaching this size by 14
months of age. Their coats are short and thick. Adult
A. nigriceps
have dark grey-black agouti pelage on the upper back and forelimbs and orange-tan
pelage on the lower back, outer rear legs, and onto the tail. They have three conspicuous
black stripes that nearly converge on the forehead. Two of these stripes follow the
sides of the face to the maxilla, the central stripe extends to the bridge of the
nose. They have white patches over each eye, on the cheeks, and under the mouth. They
also have bright orange pelage on the sides of the neck and onto the ventrum, extending
from the lower neck, chest and stomach onto the arms, legs and ventral tail. Infants
and sub-adults have the same basic coloration.
Aotus
species have disproportionally large, brown eyes, consistent with their nocturnal
habits. They lack a tapetem lucidem. Night monkeys have small external ears that are
hidden by their fur. Their digits are long and thin, with straight nails and wide
fingertip pads.The second digit of each foot has a curved nail which may be used for
grooming. They have an intermembral index of 74, typical of arboreal quadrupeds.
The basal metabolic rate is 18 to 24% below that predicted for other 1 kg mammals.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
Reproduction
Black-headed night monkeys are serially monogamous; mates can be displaced due to
violence on the part of a same sex interloper. Males and females form bonds that last
until one or the other is displaced. Fruitful mating does not occur until a mated
pair has been together for one year. Males have small testicles which might be indicative
of monogamy and low mate competition. There seems to be no signal that a female is
receptive to mating and mating activity takes place both during and outside of the
estrus period. Mating encounters are short in length lasting for 1 to 9 coital thrusts.
The breeding period in the wild is between August and February, though
Aotus
species in captivity have been observed to breed year round.
- Mating System
- monogamous
Neither males or females seem to give reproductive signals and mating activity is
independent of female estrus cycles. Reproductive activity in
A. nigriceps
usually occurs between August and February and the female produces one infant a year.
Twins have been observed only rarely, in 1 out of 169 births. Males and females disperse
from their natal range as sub-adults between 26 months and 5 years of age, averaging
dispersal at 3 years old. The interbirth interval is from 166 to 419 days. The average
weight of a newborn is 90 to 150 g. Full weaning occurs at around weeks 18 to 19.
Sexual maturity is at 2 years in males and 3 to 4 years in females.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
Black-headed night monkey males are primary caregivers for their young. Females nurse
their young every 3 hours but then drive the infant away by biting their feet or tail.
Males take over care of the infant, except for nursing, after 2 weeks old. At about
8 weeks old, around the time of weaning, the males begin to drive their young away
as well. Young sometimes usurp the territories of their parents after independence.
- Parental Investment
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- male
-
provisioning
-
pre-independence
-
provisioning
- male
-
protecting
- male
-
provisioning
- post-independence association with parents
- inherits maternal/paternal territory
Lifespan/Longevity
Not much is known about longevity in
Aotus nigriceps
in the wild. Individuals in captive populations have been observed to live 15 to
20 years.
Behavior
Black-headed night monkeys are arboreal quadripeds. They are primarily nocturnal,
but have been occasionally observed during daylight hours. Black-headed night monkeys
live in small family groups, including their young and sub-adult offspring.
Aotus nigriceps
individuals are highly territorial and defend their range with vocalizations and
sexually specific aggression. Males usually attack other males and females usually
attack other females. Confrontations last from 5 to 30 minutes and end when one of
the groups leaves.
Aggression is also the means of mate displacement. A male or female will enter a territory
and fight with the resident female or male. If they are successful they will take
over the mate and territory of their rival. Interestingly, successful interloper males
will also take over the care of any infants of the previous pair.
Home Range
The home ranges of
A. nigriceps
are small, averaging 9.2 ha. Nightly path lengths vary from 340 m to 1,025 m (averaging
708 m) depending on the amount of ambient light and prevalent weather conditions.
Communication and Perception
Resonant whoops and low-pitched hoots are the most common forms of vocal communication
in
Aotus
. Whoops are usually used in intragroup encounters at the edges of territories and
are used with visual displays and scent marking before aggressive interactions. Hoots
are usually used in distance communication by unmated males and females and may be
involved in mating rituals.
Aotus
males and females use both urine and skin secretions in scent marking behavior.
- Other Communication Modes
- scent marks
Food Habits
Black-headed night monkeys are primarily frugivorous, preferring ripened Ficus fruits. They also opportunistically feed on leaves and flowers as well as moths, beetles, and spiders. However, examinations of fecal matter from A. nigriceps have not yielded significant amounts of leaf fiber or insect matter. This is different from A. vociferans which appears to be more folivorous.
- Animal Foods
- insects
- terrestrial non-insect arthropods
- Plant Foods
- leaves
- fruit
- flowers
Predation
There is little know about predation on
Aotus
species. Their nocturnality and arboreality helps to protect them from many predators.
They rarely leave the trees, only leaving to occasionally cross into other forested
areas to forage.
- Anti-predator Adaptations
- cryptic
Ecosystem Roles
Because of their frugivory, black-headed night monkeys are likely to aid in seed dispersal, although little research has been done on their ecosystem roles.
- Ecosystem Impact
- disperses seeds
Economic Importance for Humans: Positive
Black-headed night monkeys are important members of native ecosystems.
- Positive Impacts
- research and education
Economic Importance for Humans: Negative
There are no known adverse effects of black-headed night monkeys on humans.
Conservation Status
Currently, black-headed night monkeys are considered a species of lesser concern by
the IUCN. Their conservation status could change as continued development in the forested
areas in which they live affects their habitat.
Additional Links
Contributors
Tanya Dewey (editor), Animal Diversity Web.
Adam Davis (author), University of Oregon, Stephen Frost (editor, instructor), University of Oregon.
- Neotropical
-
living in the southern part of the New World. In other words, Central and South America.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- rainforest
-
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- monogamous
-
Having one mate at a time.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- arboreal
-
Referring to an animal that lives in trees; tree-climbing.
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- territorial
-
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
- social
-
associates with others of its species; forms social groups.
- visual
-
uses sight to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- scent marks
-
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- cryptic
-
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
- herbivore
-
An animal that eats mainly plants or parts of plants.
- frugivore
-
an animal that mainly eats fruit
References
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