Night monkeys
| Night monkeys | ||||||||||||
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Panama night monkey ( Aotus zonalis ) |
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Aotidae | ||||||||||||
| Elliot , 1913 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Aotus | ||||||||||||
| Illiger , 1811 |
The night monkeys ( Aotus , Aotidae) are a primate genus and family from the group of the New World monkeys . Night monkeys are the only nocturnal monkeys and besides the tarsiers are the only nocturnal dry proboscis monkeys . They are common in Central and South America , live in family groups and feed primarily on fruits. The number of species is not fully understood, currently eleven species are differentiated.
features
Night monkeys are relatively small primates. They reach a head body length of 24 to 37 centimeters, plus a 31 to 40 centimeter long tail. The weight varies from 0.7 to 1.2 kilograms. In contrast to many other New World monkeys, the sexes are almost the same size and do not differ in the color of their fur.
The fur of the night monkey is soft and dense, in the mountain species it is elongated. It is olive-brown to black-gray on the back and on the outside of the limbs and yellow-brown to orange-brown on the belly and on the inside of the limbs. The neck can be gray or reddish in color, this serves to differentiate between two groups of species (see systematics ). The tail is long and bushy, its tip is often black, unlike some other New World monkeys, it cannot be used as a prehensile tail. The legs are extended to adapt to the sometimes jumping locomotion, on the fourth toe they have a claw-like nail - analogous to the cleaning claw of the wet-nosed monkey . The thumb is only partially opposable .
The head is rounded, the ears are small and often hidden in the fur. The eye sockets are noticeably large, the eyes are large and brown. In contrast to the wet-nosed monkeys, which are often active at night, their eyes have no tapetum lucidum , but their retina is provided with rods and cones . For these reasons, the nocturnal activity should not be an original, but a secondarily acquired characteristic of these animals. However, they only have one type of cone, so their color perception is limited. There are white fields above and below the eyes and sometimes below the mouth. Three dark stripes run along the face, one across the forehead - where it can be triangularly widened - up to the nose and one outside of each eye.
The tooth formula of the night monkeys is I 2- C 1- P 3- M 3, so they have a total of 36 teeth. The central upper incisors are very large, while the rearmost molars are very small. They have a throat pouch under their chin, which is used to amplify their sounds.
distribution and habitat
Night monkeys are native to southern Central and South America. Its distribution area extends from Panama in the north to Colombia - where there is a large, not yet fully deciphered biodiversity - and from Brazil and Peru to Bolivia , Paraguay and northern Argentina in the south. However, they are missing in the northeast and eastern parts of South America. The habitat of these animals are forests, although they can occur in a wide variety of forest types. They can be seen in tropical rainforests as well as in dry, deciduous forests. In the mountains they occur at altitudes of up to 3200 meters.
Way of life
Activity times and movement
Night monkeys are tree dwellers. However, there is no height preference in the trees, but they can be at any altitude. In the branches they usually move on all fours, but can also jump well. Most nocturnal monkeys are nocturnal, only the populations in the extreme south of the distribution area have a cathemeral way of life, that is, there is no pronounced day-night rhythm.
During the rest periods they retreat to tree hollows or plant thickets. They come out of their sleeping places around 15 minutes after sunset and are active until midnight. Then they stop for one and a half to two hours before they go looking for food again. Before sunrise they retire to their resting places. They are dependent on the moonlight, their activity is restricted on very dark new moon nights.
Your nocturnal forays are up to 800 meters long, but the length depends on the season and the light. In the dry season, the distances are shorter (around 250 meters), which is due to the larger, more frequent supply of fruit. The forays in light nights are around twice as long as in dark ones. On dark nights they follow routes that they have previously marked by smell - by urinating on their paws or with the secretion of a gland under the base of the tail.
Social behavior and communication
Night monkeys live in family groups of two to five animals. These consist of a male, a female and the common offspring. Traditionally, it was assumed that males and females are monogamous , which means that the partners live together for life. At least in one species, the southern red-throated night monkey , social behavior is likely to be more flexible and there is more frequent exchange of partners. Aggressive behavior rarely occurs within the group. The group members stay close together, they never move more than 10 meters apart. They also sleep snuggled together. In contrast to other primates living in family groups, there is very seldom mutual grooming .
Night monkeys are territorial animals, the territory of a family group covers 3 to 10 hectares. The territories are defended against foreign groups. If two groups meet, for example near a fruit-bearing tree on the border of the territory, there are loud screams, ritualized jumping with straight legs, chases and fights. These arguments last about 10 minutes, neither group "wins", but both withdraw into their territory.
In addition to the screams in defense of the territory, there are also warning sounds and sounds that indicate sources of food. A series of several owl-like calls, which are mainly emitted by individual animals at night, are striking. These calls are probably used to attract a partner, the animals also owe their English name owl monkeys (= " owl monkeys ") to them.
food
Night monkeys are primarily fruit-eaters who supplement their diet with other parts of plants and small animals. They prefer small, ripe fruits and can also visit large fruit trees because their nocturnal way of life avoids competition with diurnal, more dominant species. The proportion of fruit in the diet of animals in tropical regions is higher than that of animals in regions with a seasonal climate. These also use leaves, flowers and other parts of plants - especially in the rainy season when the fruit supply is limited.
Small animals are mainly hunted at dusk. They are adept at catching flying insects from the air or chasing crawling animals on the branches. Jumpers , moths , beetles and spiders are known to be prey .
Reproduction and rearing of young
Little is known about the reproduction of the night monkeys in the wild; almost all research comes from animals in captivity and could differ considerably from animals living in the wild.
In captivity, births can occur year round. The animals in the climatically fluctuating northern Argentina have a fixed mating season, the births fall at the beginning of the rainy season between September and November. It is unclear whether reproduction is seasonal for all species, or whether it can occur year-round for species in tropical regions. The males produce very little sperm , possibly an adaptation to the monogamous lifestyle. Since they only reproduce once a year and with only one female, higher sperm production would be a waste of energy.
After a gestation period of around 130 to 140 days, the female usually gives birth to a single young. Twin births do occur but are rare. The birth interval is around 12 months, which means that the female can carry a child every year. Newborn night monkeys weigh around 100 grams and instinctively cling to the mother's belly. But after just a few days, the father begins to take over the main responsibility for the boy. It is he who carries the boy around, lets him sleep cuddled up and plays with him, and he only gives it to the mother to suckle. In the first few weeks of life, the older siblings who are still in their birth group sometimes also carry the young, later it becomes too difficult for them. After three to four weeks, the young animals no longer cling to the father's stomach, but ride on his back. They start eating solid food at the latest at six weeks, and at five months they are no longer carried, but move independently. But they are finally weaned at around seven months. The mortality of the young animals in the first six months of life is very low compared to other primates, which is probably due to the intensive parental care.
Sexual maturity occurs at the age of one to two years, but night monkeys are not fully grown until they are four to five years old. Both male and female pups leave their birth group at around two to three years of age. Even before this, they increasingly distance themselves from their parents, they separate from them more often and also sleep in different trees. After the separation, they initially live solitary until they can find a partner and establish their own territory.
Life expectancy in the wild is unknown, a female over 13 and a male over 11 were still able to reproduce. In human care, these animals can live to be over 25 years.
Night monkeys and humans
Since the 1960s, night monkeys have been used intensively in animal experiments , especially in malaria research . For this purpose, wild animals were originally hunted, which has decimated the populations in some places. However, this practice is now prohibited by the United States and most South American countries. To a lesser extent, the animals are hunted for their meat and fur, and young animals are sometimes caught and made into pets , which is often accompanied by the killing of the parents. The Colombian species are also suffering from the armed conflict there , making it difficult to implement protective measures. The greatest threat today is the progressive destruction of their habitat through deforestation. However, due to their adaptability to different forest types, they are less endangered than other American primates. Information on the exact degree of endangerment can hardly be given for some species due to the unclear distribution area. The IUCN lists four types (Brumback-, Grauhand-, Colombian and Andean Nachtaffe) as "endangered" ( vulnerable ) and two more (Panama and Hernández-Camacho Nachtaffe) "there is insufficient data" ( data deficient ).
Systematics
The night monkeys are counted among the New World monkeys (Platyrrhini), sometimes the name Nyctipithecidae is used instead of Aotidae for the family. Their sister group are either the capuchin monkeys (Cebidae) or the common taxon of capuchin and marmosets .
The number of species is unclear. All populations are similar in appearance, but differ in the number of chromosomes . Overnight monkeys are divided into two groups based on the color of the throat, a more primitive gray-throated group, whose representatives live north of the Amazon , and a red- throated group south of the Amazon. In older systematics, sometimes all animals or at least all gray-throated and all red-throated night monkeys are grouped into one species each. Investigations of the karyotype have led to the discovery of several externally similar species, so that the exact number and range of the respective species is unclear. The following system is used for the Graukehl group Defler & Bueno (2007) and the Rotkehl group Wilson & Reeder (2005)
- Gray-throated night monkeys
- Colombian night monkey ( Aotus lemurinus )
- Panama night monkey ( Aotus zonalis )
- Hernández camacho night monkey ( Aotus jorgehernandezi )
- Gray-handed night monkey ( Aotus griseimembra )
- Brumback night monkey ( Aotus brumbacki )
- Spix's night monkey ( Aotus vociferans )
- Eastern gray-throated night monkey ( Aotus trivirgatus )
- European red-throated night monkey
- Southern European robin night monkey or azara night monkey ( Aotus azarae )
- Andean night monkey ( Aotus miconax )
- Nancy Ma night monkey ( Aotus nancymaae )
- Black-headed night monkey ( Aotus nigriceps )
literature
- Thomas Geissmann : Comparative Primatology. Springer-Verlag, Berlin et al. 2003, ISBN 3-540-43645-6 .
- Ronald M. Nowak: Walker's Mammals of the World. 6th edition. Johns Hopkins University Press, Baltimore MD 1999, ISBN 0-8018-5789-9 .
Individual evidence
- ↑ Figures from Geissmann (2003), p. 152
- ↑ a b c K. A. Cawthon Lang: Primate Factsheets: Owl monkey ( Aotus ) Behavior
- ↑ Nowak (1999), p. 552
- ↑ Search for “Aotidae” in the IUCN Red List of Threatened Species . Retrieved December 14, 2008.
- ↑ Geissmann (2003), p. 134
- ↑ Thomas R. Defler and Marta L. Bueno: Aotus Diversity and the Species Problem . Primate Conservation 2007 (22): 55-70. PDF ( Memento from February 11, 2012 in the Internet Archive )
- ↑ Don E. Wilson, DeeAnn M. Reeder (Ed.): Mammal Species of the World . A Taxonomic and Geographic Reference. 3. Edition. Johns Hopkins University Press, Baltimore 2005, ISBN 0-8018-8221-4 .
