Come i tarsi, pur essendo una specie notturna manca del tapetum lucidum tipico degli animali notturni ad esempio, i lemuri ne sono provvisti : sopperisce a questa mancanza con le grandi dimensioni degli occhi. Biologia[ modifica modifica wikitesto ] Come tutte le specie congeneri , si tratta di animali esclusivamente notturni. Vive in coppie od in piccoli gruppi familiari formati da una coppia coi propri cuccioli e subadulti, che si mantengono in contatto con tutta una serie di richiami. Alimentazione[ modifica modifica wikitesto ] Questi animali hanno una dieta prevalentemente frugivora, ma non disdegnano nutrirsi anche di altri materiali vegetali foglie, germogli ed anche di insetti.
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Within the genus, there are two groups of owl monkeys, the gray-necked lemurinus and subspecies, hershkovitzi, trivirgatus, and vociferans , found north of the Rio Amazonas Amazon River and the red-necked miconax, nancymaae, nigriceps, azarae and subspecies , found south of the Rio Amazonas Groves Because this change in taxonomy was introduced fairly recently and is disputed, some published research continues to refer to the entire group as A.
It may be necessary to generalize about some of the characteristics of owl monkeys because of the confusion of taxonomy in the literature in addition to the limited published information about this taxonomic group Wright ; Sussman MORPHOLOGY Separated into two groups based on their coloration, karyotype , and geographic distribution, owl monkeys have gray-tan to brown bodies and either gray or red fur on the sides of their necks Ford They have pale yellow to orange fur on their stomachs, underarms, and inner legs, light gray to white markings above and below their eyes, and three conspicuous, black stripes from the top of their head to either side of each eye and straight down the forehead between the eyes to the bridge of the nose Ford ; Rowe ; Groves Their coats range in thickness and length depending on the altitudes at which they are found, with species living at higher elevations having thicker, shaggier coats than those living at sea level Wright ; Groves They are unusual in their appearance compared to other primates because of their disproportionately large, brown eyes which have evolved as an adaptation to their nocturnal lifestyles.
All owl monkeys are at least somewhat nocturnal and they are the only New World monkeys active at night Wright While a nocturnal lifestyle is associated with primitive primates like prosimians , owl monkeys are not primitive but rather they re-evolved nocturnality from diurnal ancestors Wright ; Rowe Changes in the morphology of the eye and brain of owl monkeys reveal how specialized they have become to keep this nocturnal lifestyle but also reveal structural commonalities between other diurnal primates Rowe To see objects in low light levels, owl monkeys have evolved large eyeballs, their lenses have a more spherical shape than is seen in diurnal primates, and there are also more rods and fewer cones Noback Though they do see in color, owl monkeys have less acute color vision than other primates.
This is not a disadvantage as they are faster at locating and following moving objects at low light levels and have better spatial resolution at low light levels than other primates which helps them capture insects and move through arboreal habitat Wright Photo: Luiz Claudio Marigo There is very limited data on body size and weight for Aotus, most measurements from wild animals are extrapolated from only a few samples. Owl monkeys are not sexually dimorphic so males and females are about the same size and weight Wright Average male A.
Wild A. The weights from one wild A. Data from wild A. The weight of one male A. There is a fair amount of information available on the body weights of A. The weights of wild A. Male A. There are no data available for A. Owl monkeys move quadrupedally on branches and vines in the forests in which they live and are skilled leapers, able to cross gaps in the canopy up to four meters wide Wright The maximum recorded longevity for a captive owl monkey is 20 years Rowe The only data on their longevity in the wild comes from an A.
The other gray-necked species include A. All of the gray-necked species live north of the Amazon River while the red-necked owl monkeys are found south of the Amazon. Little research has been conducted on Aotus in the wild probably primarily due to the difficulty of studying nocturnal primates Sussman They tend to inhabit areas of high plant species diversity with a relatively dense canopy and will forage at all canopy levels Kinzey In Peru, they specifically prefer two types of habitats: lowland forest that is flooded seasonally or highland forest that is never flooded.
In the flooded forest, where water can be as deep as seven meters In Colombia, Aotus species are found in high, primary forests and in remnant and older secondary forests, but not in young secondary forests with low species diversity. In Argentina, Aotus is found in both high and low forests as well as gallery and island forests with dense canopies Wright ; Fernandez-Duque et al. In Brazil, A. All of the habitats in which they are found exhibit seasonal patterns of rainfall and temperature changes, with the rainy season generally lasting from about September to about May and the dry season occurring during June through August Wright Adopting a system of nocturnal behavior seems disadvantageous to animals like primates that have a high dependence on vision: food, including insects, animal prey, and fruit, is more difficult to find at night, locomotion through the forest canopy is significantly more dangerous in dim light, and a different set of environmental conditions such as cooler temperatures, differences in humidity, competitors, and predators pose threats Wright Despite these obstacles, the fossil record proves that owl monkeys assumed this nocturnal role from diurnal ancestors and, based on their wide geographical distribution, have been successful in exploiting this niche.
Many of the ecological and behavioral characteristics of Aotus can be explained or at least linked to their unique pattern of life. Though most species of owl monkeys are nocturnal, A.
Because of its range in the very seasonal Chaco of Argentina and Paraguay, the ability to forage during daylight hours is probably an adaptation to avoid activity on extremely cold, moonless nights Fernandez-Duque After leaving the sleeping site, groups travel and feed until about midnight, when they stop to rest for 90 to minutes. Owl monkeys are frugivores and supplement their diet with flowers, insects, nectar, and leaves Wright ; They prefer small, ripe fruit when available and in order to find these, they forage in large-crown trees larger than ten meters [ Seasonal availability of fruit varies across environments.
Aotus species in tropical forests eat more fruit throughout the year because it is more readily available compared to the dry forests where fruit is limited in the dry season and owl monkeys are more dependent on leaves Wright It is difficult to quantify leaf and insect eating during the night, though, and researchers sometimes have to rely on fecal sample composition to project quantity and therefore importance to owl monkeys.
Insect foraging occurs at dawn and dusk. Rather than seeking out insects in holes and crevices, owl monkeys are adept at grabbing flying insects out of the air or snatching them off of a branch Wright Moths are active at night, orthopterans call loudly at night, exposing their location, and beetles are active at night are easier making them easier to see Wright After spending the night traveling, foraging, resting, and socializing, as dawn approaches owl monkeys increase their activity levels, and forage as they travel to either the same sleeping site from the previous day or another one within their home range Wright Owl monkeys spend most of their time foraging and sleeping above in the high canopy, above ten meters Home ranges of owl monkeys are smallranging between.
The average nightly range is about of m per night. This use of space indicates that they spend more time resting and rely on fewer resources during the dry season, but resource availability is not the only factor influencing nightly travel distance.
Nightly path length is also correlated with available light; the distance traveled is directly linked to the amount of moonlight on a given night. Owl monkeys travel twice as far on bright nights with full moons than on dark nights, and they concentrate their movement during the times of night with the most moonlight Wright ; Fernandez-Duque Even though they do not travel as far, they still need to move on dark nights to find food and one adaptation to this need to forage is to travel the same routes repeatedly.
They probably memorize routes and use chemical cues to help them find their way between food sites and sleeping sites Wright Aotus azarae azarae Photo: Eduardo Fernandez Duque Though owl monkeys are sympatric with other primates that use similar resources, they do not compete for access to resources because of their alternative schedules. Furthermore, non-primate nocturnal competitors are usually small-bodied like bats or forage alone or in pairs, not posing a significant source of competition Wright Nocturnal predators do not usually eat monkeys, but some potential threats include owls, snakes, and felids.
Diurnal raptors may pose a threat to owl monkeys if they are not well hidden in their sleeping sites Wright ; Owl monkeys have been successfully employed in biomedical research on malaria since the s because of their natural resistance to the parasites that cause the disease Ford Reviewed by Eduardo Fernandez-Duque.
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Brumback's night monkey
Faejind Sign up to our newsletter Get the latest wild news direct to your inbox. Vision Research, 33 Grey-legged night monkey Aotus griseimembra. MyARKive offers the scrapbook feature to signed-up members, allowing you to organize your favourite Arkive images and videos and share them with friends. Wild boar Sus scrofa.