What kind of animal is the night monkey? We will explain its characteristics, ecology, and habitat. It is a very unique animal, being the only nocturnal monkey. This monkey species is widely found in South America and is known to live in deep tropical rainforests.
What is Yozaru? Basic Stats
The night monkey is a primate belonging to the Capuchin family and Aotus genus of the order Primates. Its English name is night monkey, and its scientific name is Aotus trivirgatus. Its body length is 30-40cm, and its weight is 600-1,000g.
| Japanese（和名） | ヨザル |
| English（英名） | night monkey |
| scientific name(学名) | Aotus trivirgatus |
| classification（分類） | Mammalia、Primates、 Cebidae、Aotus 哺乳綱、霊長目、オマキザル科、ヨザル属 |
| IUCN Status(保全状況) | LEAST CONCERN |
| Length（体長） | 30～40cm |
| Weight（体重） | 600～1,000g |
Owl monkey taxonomy (zoological classification)
例として代表的な「ロリス属」を挙げると：
界：動物界 (Animalia)
門：脊索動物門 (Chordata)
綱：哺乳綱 (Mammalia)
目：霊長目 (Primates)
亜目：真猿亜目 (Strepsirrhini)
科：メガネザル科 (Lorisidae)
属・種：ロリス属 (Loris)、ガルゴ属 (Nycticebus) など
Habitat
Owl monkeys are found in Colombia, Venezuela, and Brazil. Pairs are often seen in South America, and research on them is also progressing.
- Geographic Distribution
Owl monkeys are widely distributed, mainly in Southeast Asia.
India and Sri Lanka: Southern part of the Indian subcontinent
Southeast Asia: Thailand, Malaysia, Indonesia (Sumatra, Java, Borneo, etc.)
Philippines: Some island regions
💡 Key Points: Mainly found in tropical and subtropical regions near the equator
- Habitat
Tropical rainforests and secondary forests: Prefer forests rich in evergreen trees and bamboo groves
Environments suitable for arboreal life
Dense forests where they can easily hang from tree branches and move between them
Hide during the day
They stay still in the shade of leaves and branches to protect themselves from predators
They also prefer to live near water sources
- Ecology
Because they are nocturnal, it is important for them to hide and rest during the day.
Forest structure and thickets are also important for them to secure food (insects, fruit, etc.)
Habitat reduction due to human activity and deforestation makes survival difficult
What are its characteristics? What kind of creature is it?
Night monkeys are the only nocturnal monkeys and spend most of their time in the trees. Their coat is silvery gray or gray-brown on the upper side and orange to brown on the underside. Their heads are round and their ears are buried in the fur. They have five fingers on their limbs and flat nails, making them good at climbing trees. Night monkeys live in forests and highlands.
- Physical Characteristics
Body Size: Small to medium (approximately 18-40 cm in length, short or almost no tail)
Weight: Approximately 0.3-1.5 kg
Fur Color: Brown to gray, with camouflaged patterns on the body as protective coloration
Large Eyes: Adapted to nocturnal behavior, they can see well even in dark forests.
Dexterous Limbs: Suitable for climbing trees and grasping branches.
Tail: Most are short; even long tails are not used for preying.
💡 Key Points: Their large eyes and dexterous limbs are specialized for nocturnal and arboreal behavior.
- Personality and Behavioral Characteristics
Timid and Cautious: Highly sensitive to predators and humans.
Nocturnal: Becomes active after dark and rests among tree branches and leaves during the day.
Quiet and Discreet: Quiet calls make them less likely to be noticed.
Living alone or in small pairs: Less social.
- Diet
Omnivorous, but prefers insects and tree sap.
Insects, small invertebrates, fruit, tree sap, etc.
When searching for food, they carefully feel around for food with their hands and feet.
- Notable Characteristics
As nocturnal monkeys, they are extremely quiet and cautious.
Despite their small size, they are adept at navigating tree branches.
Large eyes allow them to navigate in the dark.
Despite their small size, they can efficiently live in the forest understory.
What is their personality like?
Night monkeys are completely nocturnal animals, sleeping curled up in tree holes during the day, but are active at night, which is the opposite of humans. They usually live in groups, making them very social animals. Their range of movement is 200 to 250 meters and they have a strong sense of territory.
- Timid and cautious
Highly sensitive to predators (such as mountain lions, snakes, and large birds) and humans
Early sensitive to sounds and noises, they will quietly hide if they sense danger
Often stay still in the forest understory
💡 Key point: To survive in the wild, they are constantly on the alert for their surroundings
- Nocturnal and reserved
During the day, they rest among tree branches and leaves, making them inconspicuous and quiet
Active at night, but their calls are quiet and reserved
Very rarely aggressive, avoiding conflicts
- Cautious and observant
Move quietly, carefully moving between branches and leaves
Acts by carefully observing their surroundings and the movements of predators
Highly skilled at avoiding danger
- Social
Live alone or in pairs
Rarely form groups
Not as sociable as other monkeys, they prefer an independent lifestyle
What is their ecology like?
Night monkeys are omnivorous, surviving by eating fruit and leaves, as well as honey, insects, frogs, snails, and small birds. The gestation period is 150 days, and females can give birth to one baby at a time. They reach sexual maturity after 2 to 3 years. They have a lifespan of 10 years.
- Behavior
Nocturnal: Becomes active after dark and rests among leaves and branches during the day.
Solo or Pair Activity: Less social, they are generally solitary except during mating season.
Activity Range: Moves in the dense forest understory.
Moves quietly using tree branches and shrubs.
- Habitat/Hiding Places
Living hidden in the forest understory.
Hides among leaves and branches to protect themselves from predators.
Moves almost motionless during the day and searches for food at night.
- Diet
Omnivorous, but consumes mainly insects and tree sap.
Insects, small invertebrates, fruit, tree sap, etc.
Uses dexterous limbs to search for and gather food.
Do they have any natural enemies?
Predators include jaguars, wolves, and leopards.
About Baby Otter Monkeys
This article provides detailed information about baby Otter Monkeys (small nocturnal monkeys, particularly those of the loris and galgo genus). Compared to adult monkeys, they are smaller, and their behavior and ecology are slightly different.
- Birth and Development
Gestation Period: Approximately 6-7 months
Litter Size: Usually 1, rarely 2
Birth Weight: Approximately 100-200 g
Birth Length: Approximately 10-15 cm
💡 Key Points: Very small, they grow up under the protection of their mother
- Appearance
Soft, brown to gray fur with light markings
Large eyes, adapted to nocturnal behavior, give them a cute, round appearance
Their limbs and claws are underdeveloped, and they require their mother’s assistance for climbing trees and foraging
- Behavior
Dependent on their mother
When threatened, they will hide on their mother’s back or among the leaves
Learn how to find food and how to move around in the forest from their mother
Through play and imitation, they learn tree climbing, branch movement, and vigilance
They gradually acquire nocturnal behavior patterns
- Time to Maturity
Young animals become independent after about a year.
During this time, they learn skills from their mothers, such as foraging for food and avoiding predators.
They gradually acquire the same cautious and timid personality as adults.
Are owl monkeys an endangered species?
Owl monkeys are not designated as an endangered species.
- International Assessment (IUCN Red List)
Galgo (Nycticebus, commonly known as slow loris)
Assessment varies by species
Slow loris (Nycticebus coucang): Vulnerable (Endangered)
Slow loris in Indonesia’s Borneo and Sumatra islands are Endangered (Endangered)
Major causes of decline:
Deforestation (farmland development and logging)
Pet trade and illegal hunting
Loris
Some species in India and Sri Lanka are also Vulnerable (Endangered)
Habitat loss and illegal hunting are the main threats
- Population Status and Distribution
Distribution ranges from Southeast Asia to India and Sri Lanka
Populations are declining locally due to deforestation and human activity
Natural populations are being pressured, particularly by the large number of individuals being captured for pets
- Threats
Deforestation: Farmland expansion, logging, urbanization
Illegal pet trade: Popular due to their cute appearance
Natural predators: Large birds and snakes in their natural environment
Because they are not aggressive, their main defense against predators is hiding.
Can owl monkeys be kept as pets?
Owl monkeys live in groups, so they are not suitable for the general public to keep as pets. We recommend viewing them at a zoo or similar place.
- Personality and Behavioral Issues
Timid and cautious
Sensitive to humans and noise, easily stressed
Low aggressiveness, but nervous
Excessive contact and changes in environment can be detrimental to their health
Nocturnal
Because they are nocturnal, they sleep quietly during the day, but a home environment can be stressful due to their out-of-sync rhythms
💡 Key Point: Due to their nervous and timid nature, they are not suitable for domestic captivity
- Environmental Issues
They require ample space to climb trees and walk across branches
They become constantly stressed without hiding places (bushes or branches)
Because they are nocturnal and quiet, it is difficult to adjust their environmental stimuli
- Laws and Regulations
Most Owl Monkeys are protected species
Import and breeding are restricted in Japan under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)
Private captivity is generally prohibited
Breeding in zoos and research institutions is permitted only with special permission
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