Last modified on 06/05/02

New World Monkeys

Taxonomy    

Diet and feeding

Callitrichids (marmosets and tamarins)

Cebids

Taxonomy

Of the six families of anthropoids (as opposed to prosimians), two are found only in the New World tropics (Callitrichidae and Cebidae); these are referred to commonly as "New World monkeys". Two families are found only in the Old World of Africa and Asia (Cercopithecidae and Pongidae), one is restricted to Asia (Hylobatidae), and Hominidae is globally distributed.{4048}

Suborder Anthropoidea, Infraorder Platyrrhini (New World monkeys)

Platyrrhines are called that because their flattened nostrils face forward. None have ischial callosities or cheek pouches like the Old World monkeys. Their digits have flat or curved nails. There are 19 genera, 100 species and 205 taxa. Traditionally they have been divided into two families, Callitrichidae and Cebidae. However, a more phylogenetic approach identified three clades which some authorities consider to be distinct families: Cebidae (marmosets, tamarins, capuchins and squirrel monkeys), Atelidae (howler monkeys, spider monkeys, woolly monkeys and muriquis), and Pitheciidae (uakaris, sakis and titis). Morphological descriptions and molecular genetics have affirmed this classification with the exception of the night monkey (Aotus), which may be a very early offshoot and worthy of its own family.{4048}

Callitrichids:  Family Callitrichidae has the following characteristics: 

Hershkovitz divided the family into the tamarins (Saguinus, with spatulate incisors and well-developed canine teeth) and marmosets (Callithrix, with caniniform incisors and indistinguishable canine teeth).  Goeldi's monkey (Callimico) is unusual in that its habitat is restricted to the upper Amazon, it has 3 molars, and it has only a single offspring while other callitrichids have twins. The lion tamarin (Leontopithecus) is restricted to Brazil's Atlantic forest, and they are critically endangered.{4048} The National Zoo in Washington, D.C., has a small group that they are preparing for release into the wild.

Cebids: Family Cebidae is much more diverse, with several subfamilies: squirrel monkey (Saimiri), capuchin (Cebus), titi monkey (Callicebus), saki monkey (Pithecia), bearded saki (Chiropotes), uakari (Cacajao), night monkey (Aotus), howler monkey (Alouatta), woolly monkey (Lagothrix), muriqui (Brachyteles) and spider monkey (Ateles){2765}{4048}

The night monkey (Aotus) is the most difficult of these to classify, as it is the only nocturnal platyrrhine. Morphological and molecular genetic studies suggest it is a very early offshoot of the suborder.{4048}

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Diet and feeding habits

According to Nowak{4048} there are three main food sources for primates: faunivores eat small animal prey such as insects, small vertebrates and birds' eggs which provide a source of protein, lipid and essential amino acids; frugivores eat fruit and seeds providing carbohydrate and some lipid; and folivores, which eat leaves and flowers for carbohydrate and protein. All primates eat fruit, seeds and leaves except the tarsiers, which are entirely faunivorous.

Diet and GI tract anatomy are related. Anterior dentition is extremely important in obtaining food, and varies with the species' dietary habits. Posterior dentition is used to process the food, and also varies according to the major diet components. In faunivores the gut is dominated by the small intestine; the stomach and colon are reduced and the cecum may be absent. Folivores need either a large complex stomach (i.e. langurs and colobines), or a large cecum and colon (i.e. howler monkeys, gorillas and Lepilemur) to enable digestion of cellulose and lignin. Frugivores have intermediate GI tracts; the stomach and large intestine are larger than those of the faunivores.{4048}  

Galagos and small New World primates such as squirrel monkeys, marmosets and tamarins are highly insectivorous and supplement that diet with fruit or gums, especially that of the acacia tree . Gums are complex polysaccharides and require symbiotic bacteria for digestion within the cecum. The primate obtains gum from trees damaged by weather or insects, although Cebuella and Callithrix have elongated lower incisors and incisor-like canine teeth with which they gouge the tree. This allows these species to obtain gums year-round and expands the habitat in which they can live. Nectar is also an important source of carbohydrate for primates, making them act as pollinators in the process.{4048} 

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Callitrichids (marmosets and tamarins)

Anatomy        Physiology    Behavior        Use in research         Common diseases

Callitrichid Anatomy

Callitrichids (the family may be spelled either Callitrichidae{2765} or Callithricidae{3562}) are the smallest and most primitive of the simians. They look more like squirrels than monkeys. The taxonomic tendency is to name relatively few genera but many subspecies; the animals have many colors and types.{2765}

This is Callithrix jacchus jacchus, the white-ear tufted marmoset (or common marmoset), which is agouti gray in body color. It is the most important laboratory species of marmoset, as it is easy to maintain in captivity.

Marmosets are diurnal, sleeping in trees during the night. Their diet includes insects, spiders, small vertebrates, bird eggs, fruit and tree exudates. Their lower canine teeth are specialized for perforating tree bark, and they spend about 70% of their foraging time obtaining tree exudates. They are on appendix 2 of CITES, except C. aurita and C. flaviceps which are on appendix 1.{4048}

C. geoffroyi , below, has blackish circumauricular tufts, white or creamy crown and sides of the face.

Marmosets have claws rather than nails, making their tree-climbing resemble squirrels more than primates. Callitrichid thumbs are not opposable, but their big toes have flat nails and are completely opposable. Their tails are long but not prehensile{3562}. Callitrichids have axillary mammary glands, barely-visible taenia coli with no sigmoid flexure, three premolars and two molars (opposite that of Old World monkeys and man), and a smooth cerebral cortex. Their eyes are frontally located, nostrils open sideways, and their ears are quite large but always covered by hair{3562}. Distinguishing adult males from females can be challenging when observing from outside the cage, as there is no sexual dimorphism in this species.{4588} Males have a completely scrotal penis, and females have well-developed labia majora.{2765}

There are two important genera of tamarins: (1) Leontopithecus or Leontideus{3562}(lion tamarins, at left), which are endangered; and (2) Saguinus, which has important laboratory species such as the cotton-top tamarin (S. oedipus oedipus). S. oedipus belongs to the "bare-faced" section, and has a prominent crest of white hair extending back over the head. S. bicolor, S. oedipus, and S. geoffroyi are endangered due to habitat destruction and are on appendix 1 of CITES.  S. oedipus were also decreased in numbers due to taking from the wild for the animal trade. It is unlikely that the natural habitat of S. oedipus can be restored, since remaining forest tracts are too small to support populations.{4048}{2765}

Tamarins have longer limbs and are better at jumping than marmosets.{3562}

S. mystax, at left (cover of CTLAS 35(1)).

S. imperator, the emperor tamarin, is shown below right. S. imperator belongs to what Hershkovitz called the "hairy-faced" section of the tamarins; it has a long white mustache which extends to the shoulders.

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Callitrichid Physiology

In nature callitrichids are omnivorous, feeding on tree gums, insects, small animals and fruit. Tree gums are rich in sugar and minerals and can make up most of the diet in season. Although commercial diets are available, they are often supplemented because our knowledge of callitrichid nutrition is sketchy. Callithrix prefers sweetened water and food sources over unsweetened ones. Many manufactured diets are high in protein although there is little basis for this. Most facilities use varied diets rather than strictly using commercial biscuits; for example, one such diet consists of Monkey Chow (25% protein), water, bananas, apple sauce and Karo syrup and afternoon supplements of canned Zoopreme Marmoset Diet, eggs, peanuts, mealworms, raisins, coconuts, lettuce, sweet potatoes or suckling mice.{2765} Another facility feeds Purina New World Monkey Pellets #5040 ad lib, with alternating supplements of apples and bananas, waxmoth larvae, and vanilla yogurt. Acacia gum (available from Bio-Serv) can be given in enrichment feeders; it may provide not only behavioral but nutritional enrichment, as such gums are high in calcium and divalent cations to balance the high phosphorus present in insect diets.{4118} New World primates require vitamin D₃ supplementation as well as vitamin C.{3563}

Wasting marmoset syndrome was a problem in wild-caught animals, with signs of weight loss, alopecia, and diarrhea. It was found that S. mystax, at least, requires a much higher caloric intake than previously thought. Provision of 335kcal/kg reversed much of the syndromic signs.{4076}

Normal body temperature in callitrichids ranges from 38.5°-40.0°C; the wide range may reflect the stress of catching.{4762} They develop a distinct torpor when asleep, and their body temperature can drop to 34.0°C. {2765} Callitrichids need to be kept relatively warm, as they will become stressed at <32°C. Cold stress has been postulated as a contributing factor in chronic colitis.{4762}

Husbandry is a critical factor in the successful maintenance of callitrichids, and frequent (weekly) sanitation is required. Much is based on their arboreal habitat: high cages, high placement of feeders, many perches, a flat-bottomed nest box for sleeping and capture, and a varied but high-energy diet. Animals must be housed singly to prevent fighting, unless they are kept in stable family groups of two parents and their offspring. They should be fed twice daily to keep their energy levels high. They are diurnal, so feeding should be done first thing in the morning and again late in the afternoon. Ambient temperatures should be a little cool (22.2°-23.8°C) with 50% relative humidity. To stimulate vitamin D activation, ultraviolet lamps should be provided for 30-60 minutes per day; this may alleviate cage paralysis (osteodystrophia fibrosa) and promote sunning behavior and grooming.{2765}

Reproduction

Callitrichids can be the most prolific of simians. Males reach sexual maturity later than females, usually around 18 months; females may become pregnant at 1 year of age but it is better to wait until 2 if possible. Callitrichid females do not menstruate, have sex skin to indicate estrus, or show vaginal cytologic changes; hormone levels can be measured to demonstrate cyclicity. The estrous cycle lasts 14-18 days. Lactation does not cause anestrus, so short inter-birth periods are the norm. Gestation is 128 days in Leontopithecus, and 145 days for most of the other species. Pregnancy is easily detected by abdominal palpation as early as 2 weeks (but more often 30-45 days). Twinning is the rule in more than half of callitrichid births, with triplets and occasional quadruplets. The placenta is monodiscoid hemochorial. The placenta is unique in that it has vascular anastomoses between the twins, and placental hematopoiesis. This means that stem cells can cross over between twins, creating chimeras. The normal chromosome number is 44-46 depending on genus. Delivery normally takes place at night, outside the nest box. During parturition, heart rate and diastolic blood pressure increase, whereas systolic blood pressure decreases. Parturition can be divided into three phases: preparation for birth (extreme restlessness), dilatation (freezing of locomotion, heavy breathing, open mouth), and expulsion (strong contractions lasting 10-20 seconds).  Normal delivery takes only about 20-25 minutes.{4547} The neonates must climb to the mother’s nipple or risk not surviving. Abortion with retained placenta is a medical emergency due to risk of exsanguination. Mothering ability is a problem, especially with primiparous females. The family helps raise the infants. Weaning is usually complete by 60 days of age.{2765}

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Callitrichid Behavior

New World monkeys are almost strictly arboreal, and much of their successful husbandry depends upon this feature. They are very territorial in captivity, and can make loud noises when disturbed. Human traffic in the colony must be kept to an absolute minimum. They also depend greatly upon auditory communication.{2765}

Housing should be either singly or in breeding family units, to avoid severe fighting. At least one perch must be provided, as must a nesting box with a flat surface. To capture an animal, bait it into the box and remove the box from the room, as the rest of the animals will become extremely upset if manual capture is attempted. Feeding cups will be used only if located high in the cage, and several at wide spaced intervals must be provided to breeding families. Provision of UV lamps for 30-60 minutes per day seems to encourage grooming and sunning.{2765}

Marmosets usually live in small family groups dominated by a monogamous pair.  Tamarins may have non-family members in their groups, and they all get along well together. They have overlapping territories in the forests, and they do not defend their territories. Ovulation may be suppressed in subordinate females, presumably by pheromones from the dominant female. They have scent glands which they use the same way tamarins do, rubbing the secretions on objects to convey information and mark territory.{4048}

In captivity, subordinate female marmosets do not ovulate due to hormonal differences compared to dominant females. Subordinate males are also reproductively suppressed, but hormones are not involved; it appears to be a mechanism to avoid incest.{4744}

Mothering ability is a problem in callitrichids, especially primiparous ones. The entire family plays a role in raising of infants, and it is believed that learned behavior is critical if they are to be successful parents. Food sharing is a common behavior, particularly with males providing food for the young.{2765} In nature, the father and others assist at birth, washing the infant and carrying it between feedings. Such communal behavior is apparently more important in Saguinus than in Callithrix.{4048}

Dominance in families is subtle. Males show habits typical of all simians, namely defense, stabilizing the position of the dominant female, and decision making. Males respond to distress aggressively, whereas females tend to dominate feeding stations. All callitrichids mark their territory using circumgenital and sternal glands, by rubbing the chest, genitalia or pubis on the object. Females tend to mark more frequently than males. Urine marking is also used. Marmosets (not tamarins) posterior present, displaying their genitalia to a perceived threatener. Family aggression is usually non-destructive and brief in duration. Allogrooming and play are also normal behaviors.{2765}{4048}  

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Use in Research

Marmosets

Tamarins

Saguinus and other callitrichids have been used to study hepatitis (hepatitis A in Saguinus, hepatitis C in marmosets{3958}), slow virus disease, spongiform encephalopathy, malaria, Mycoplasma, Chlamydia, cholera, and viral oncology. Epstein-Barr virus can cause malignant lymphoma or regressing lymphoreticular neoplasia, and understanding this is an important link to neoplasia in man associated with the virus.{2765} 

Common Diseases

Enteric diseases

Bacterial: Klebsiella pneumoniae is a common cause of lobar pneumonia in otherwise sick or debilitated callitrichids. Some animals are shedders. Uncommonly, Salmonella and Shigella occur in unhealthy populations. Five tamarins (S. oedipus) that were positive for Campylobacter died in 10 weeks with bloody diarrhea; antibiotic therapy contributed to the development of pseudomembranous colitis, weight loss, weakness and collapse due to toxins from Clostridium difficile.{3892} Infection with C. coli is more prevalent than with C. jejuni. Campylobacter infections and reinfections with multiple strains are common among laboratory-housed primates. Infections were most prevalent between 3 and 9 months of age; the association between diarrhea and infection varies. Season of the year is an important factor; C. jejuni infection most frequently occurred between April and June whereas C. coli infections occurred between October and December. No association between the infections and diet or idiopathic colitis was observed.{4487} Yersiniosis was diagnosed as the cause of annual mortalities in a Dutch colony of marmosets and tamarins.

Tuberculosis has not been diagnosed except in a case of cutaneous tract in a cotton-top tamarin. Infraorbital abscesses, usually associated with canine teeth, are a common problem in saddle-back tamarins (S. fuscicollis); however tooth problems are not usually the cause in this species. Abscesses are more likely associated with the paranasal sinus or osteomyelitis. Fight wounds can cause osteomyelitis, either local or systemic, which usually respond well to appropriate antibiotics. The tail tip may become infected due to perches that are not sufficiently high; feces accumulates and may lead eventually to localized osteomyelitis. Partial tail amputation is not indicated, as first-intention healing is difficult to achieve; rather, it is suggested that local and/or systemic antibiotic therapy be used and the bone sequestrum removed under light sedation when it is ready to come out.{2765}  

Parasitic: Although there are a number of internal parasites in wild-caught animals, most are not pathogenic for the animals. Many callitrichids are infected with Trypanosoma cruzi, but disease is rare. Similarly, toxoplasmosis, Entamoeba histolytica, and Pneumocystis carinii have been found, but have not been associated with significant disease. Filarial worms (Dipetalonema, Filaroides), cause problems if the microfilaria interfere with the research being conducted. The most common and serious parasite of callitrichids is the acanthocephalan Prosthenorchis, which is carried by the cockroach Blatella germanica. Once in captivity, the adults embedded in the wall of the terminal ileum tend to penetrate the wall, causing peritonitis, abscesses and sepsis. Epidemics can devastate a colony, and no available anthelmintics seem to be effective (although in this old reference ivermectin was not mentioned). The nymph form of the pentastomid arthropod Porocephalus clavatus is found as C-shaped structure adhered to organs in the peritoneal or thoracic cavities as an incidental finding.{2765}  

Viral: Herpesvirus tamarinus (aka herpes T or H. platyrrhinae) is devastating in callitrichids, and they must be housed separately from the carrier species, Saimiri. Three Gammaherpesviruses are oncogenic in callitrichids: H. ateles, H. saimiri (both rhadinoviruses), and Epstein-Barr virus (a lymphocryptovirus). A new marmoset lymphocryptovirus was described in Callithrix in Wisconsin in the early 90s; it caused lymphoproliferative disease. Measles is another serious disease to which callitrichids are exquisitely sensitive, beginning with swollen eyelids and lethargy and culminating in death in less than a day. Vaccination is protective, using inactivated vaccine (or possibly canine distemper/measles vaccine, which is more efficacious in rhesus{4037}). Parainfluenza virus types 1 (Sendai) and 3 (HA-1) have experimentally infected Saguinus mystax. Signs included sneezing, nasal discharge, cough, and conjunctivitis.{2765}

Other diseases: One of the most common causes of morbidity in callitrichids is fighting and the resultant trauma and infection. In tamarins, diarrhea is the number one cause of morbidity in individuals. Tamarins develop chronic colitis, with atony, megacolon and the production of copious amounts of feces. Histologically there is atrophy of the colonic crypts. Poor diet is considered a major factor in this disease. The cotton-top tamarin is unique among primates in its susceptibility to mucinous adenocarcinoma of the large bowel. This tumor is the major cause of death in otherwise healthy and well-maintained cotton-tops. Intussusception and rectal prolapse are common, usually occurring together. The prolapse can involve the entire colon, because of weak or vestigial hepatic and splenic ligaments. Simply reducing the prolapse is rarely effective because of the likelihood of one or more intussusceptions, so surgical cecocolopexy is indicated. In infants, the major cause of mortality is maternal neglect.{2765} 

Wasting marmoset syndrome (WMS) is the most important and least understood syndrome in callitrichids. Cardinal signs are weight loss, loss of muscle mass in the thighs, alopecia, anemia and hypoproteinemia, and hypoglycemia. Poor diet and unresolved behavioral problems may be a cause. For example, replacing a commercial closed-formula diet with an open-formula diet containing 26% protein and 6% fiber resulted in substantial weight and resolution of WMS and mortality in imported Saguinus mystax{4076}.  Assay of a commercial marmoset diet revealed high levels of gliadin-like cereal proteins, and high levels of circulating IgA antibodies and immune complexes to gliadin were assayed in marmoset with WMS. These complexes were also deposited in the glomeruli. The syndrome may be similar to a human disease called IgA nephropathy or Berger's disease{4077}. Other authors have suggested a role for the T cell receptor in the marmoset with chronic colitis and/or WMS.

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FamilyCebidae

Taxonomy     Anatomy, Physiology and Behavior (by species)  

Squirrel monkeys

Taxonomy

Physically and taxonomically, the cebids are much more diverse than the callitrichids. Most are larger than the callitrichids. They have a large range of body sizes (Saimiri to Brachyteles), one nocturnal genus (Aotus), and many (Ateles, Brachyteles, Lagothrix and Alouatta) have prehensile tails. Saimiri have very mobile but not prehensile tails. Cebus carry their tails coiled over their backs and use it to brace or steady themselves. Some taxonomists divide them into the family Cebidae (Saimiri, Cebus, Callicebus, Pithecia, Chiropotes, and Cacajao) and the larger prehensile-tailed subfamily Atelinae (Alouatta, Ateles, Lagothrix and Brachyteles). Their eyes are typically diurnal, with rods and cones; Aotus has rods only. The thumbs are never opposable, but the great toe is well-developed and is opposable. The dental formula is I2/2, C1/1, PM3/3, M3/3 = 36. Note the difference of molars from the Callitrichidae.{4048}{4163}  

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Cebid Anatomy, Physiology and Behavior

Aotus

There is profound disagreement over the taxonomy of Aotus, with some believing that the species diverged prior to the separation of Platyrrhini and Catarrhini from each other. Owl monkeys are the only nocturnal simians. The head is relatively round and the eyes very large. Some vision research has been done using Aotus. They are small animals, weighing only 0.6-1kg as adults. The densely-furred tail is not prehensile. The ears are small and are completely concealed in the heavy fur. Their hands are not very dexterous, so care must be taken to ensure that dropped food is still accessible in the cage. They are very adept at running and leaping on tree limbs. In the forest, they sleep in tree holes during the day.{2765}{4048}

Owl monkeys seem reasonably tolerant of human activity in the wild, but they are killed for their meat and fur as well as being caught for the pet trade and biomedical research. Aotus has been used for studies of malaria and eye diseases. Most that are captured die before reaching their destination. All species are on appendix 2 of CITES.{4048}

It has been difficult to raise and especially breed Aotus in captivity. In their natural habitat they form monogamous permanent pairs which may group in families with an adult pair and their young from the past 3 seasons. They must not be housed in groups, except in breeding pairs. In captivity, they display no seasonal breeding; in the wild most young are born between November and January although others have observed no marked birth season. The estrous cycle lasts 10-15 days, with no evidence of menstruation. After a gestation period of 120-140 days, infants are usually born during the daylight hours. The neonates must crawl around to the mother’s back to avoid abandonment. The females carry the infants only for a short period during nursing; the rest of the time the fathers or siblings carry them. Starting at 1 month of age, they receive food directly from their father’s mouth, although they also continue to nurse for up to 9 months. Some infants have been successfully hand-reared using human infant formula{2765}{4048}.

In their natural habitat, Aotus eat fruit, foliage, insects, small animals and birds. In captivity, commercial monkey chow may be supplemented with fruit, multi-vitamins (especially D₃ and C), meal worms, milk and eggs. Excessively high protein may cause kidney problems{3563}.

Their environment should be kept between 21° -27°C with 30-60% relative humidity. Aotus are the only nocturnal simians, so must be kept in subdued lighting conditions. Aotus have been maintained on a 12/12 light/dark cycle without using red filters. As with callitrichids, care should be taken to maintain a quiet environment, using the nest boxes to catch and remove animals from the room.{2765}

They cannot be housed together unless in monogamous pairs with families. Dominance does not appear to be a problem with adults. Self-grooming is common, and allogrooming is rarely observed. Since olfactory cues are important, Aotus scent-mark using glands on the ventral surface of the tail base.

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Alouatta

The most notable anatomic feature of Alouatta is the large resonance chamber created by the specialized hyoid apparatus, which allows them to make a long loud howl or bark. The hyoid bone and greatly enlarged thyroid cartilage form a vesicle that is 4-5 times larger in males than in females, making a sound-box. The jaw is wider and higher on the sides to accommodate this structure{3562}. Their tails are prehensile with a tactile tip; the last third of the tail is naked on the underside. The tail is very strong; a falling monkey can catch itself with only its tail.{2765}{3562}{4048} 

Alouatta caraya, at right: males are all black, and females are all yellow-brown. Range is eastern Bolivia, southern Brazil, Paraguay and northern Argentina.{4048}

Alouatta palliata, below left, ranges from southern Mexico to the northwest coast of South America. They, along with A. pigra, are endangered due to habitat destruction and hunting for meat, and are on appendix 1 of CITES.{4048}

Normally Alouatta live in large groups of up to 50 animals of both genders. The groups are territorial, defended by much howling and shaking of branches. Nowak reports that groups range from 10-20 individuals including 2-4 adult males and 5-10 adult females. Competition between males is fierce in this male-dominance hierarchy, whereas females remain peaceful among themselves. Territories overlap significantly according to Nowak, and the loud dawn chorus of calls serves to keep groups from encountering each other during daily foraging.{4048}

Females become sexually mature at 3-3 ½ years of age and have regular 16-day estrous cycles. No seasonality in breeding has been noted. Gestation is variously reported as 140 days{3562}, 186 days{2765}, or a range of 180-194 days{4048}. There is usually only one infant. Infants are tended for about one year{3562}, during which they generally ride on their mothers' backs. Almost half of infant mortality is the result of being killed by older males. They become sexually mature at about 3.{4048} 

Howlers do not spend much time grooming or allogrooming{2765}. In groups, the females seem to predominate; group numbers range from 8-40{3562}. Nowak{4048} reported that groups are male-dominated and there is considerable competition among males, invasion and infanticide. Groups consist of adult animals, with the older young leaving to form new groups. As a result, in most groups the adults are not related to each other. 

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Ateles

Ateles geoffroyi, at right, found in northeastern Mexico, the west coast of Mexico, and Panama. Subspecies A. geoffroyi frontatus and A. geoffroyi panamensis are endangered and are on appendix 1 of CITES. In many parts of their range they are avidly hunted as food, and are easy to find because of their size and noisy habits.{4048} 

Spider monkeys are extremely lanky and agile like gibbons, with long prehensile tails. The tail has a sensitive bare surface along the lower tip{3562}. Their thumbs are vestigial, and the other fingers very long. They weigh up to 6-8kg. They eat mostly fruit and leaves, and have been maintained on commercial monkey chows. They have coarse, stringy hair and no underfur. The color ranges from yellowish gray, dark gray, reddish brown, dark brown or almost black on the upper parts of the body to white or yellow on the underparts. Most have a black face with white eye rings, but some have flesh-colored faces. The female clitoris is greatly elongated, resembling the penis of the male.{4048} 

Ateles are not seasonal breeders, but infants in the wild are usually born in the fall{3562}. Menstrual cycles are 24-27 days long. Gestation is reported to be approximately 140 days{3562}, 210 days{2765}, or 200-232 days{4048}. Mothers give birth alone, returning to the group 2-4 months later{3562}. Infants nurse for about 10 months. Nowak{4048} reported that a captive A. geoffroyi lived for 48 years.

Spider monkeys tend to be adaptable to captivity and are somewhat gentle in temperament{2765}. Cages or pens should be large enough to allow spider monkeys to hang by their tails or arms and facilitate brachiation, as their tails act as a fifth limb.{2765}{3562}  

Ateles are rather gentle and adaptable simians despite their lanky appearance and agility in the trees. In the wild they are almost entirely arboreal and are entirely diurnal, eating in the morning and resting the remainder of the day except when fruit is plentiful. They have been reported to break branches up to 5kg in weight and drop them on observing humans. Their social structure is poorly understood, with group sizes ranging considerably. Some have suggested they have a fission-fusion society similar to the chimpanzee.{4048} 

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Lagothrix

Lagothrix lagothricha (or lagotricha), the woolly monkey of the Andes mountains and northern Peru. Although these species are on appendix 1 of CITES, they are unable to adapt to secondary forests, their meat is esteemed as food and their young are valuable sold as pets after the mothers are killed. It and Ateles are the first species to disappear when humans encroach on their habitat.{4048} 

Woolly monkeys weigh 5-10 kg, nearly as large as Ateles and Brachyteles. Their hair is short and thick with heavy underfur. The upper parts are gray, blue gray, tawny, dark brown or blackish brown, with slightly lighter underparts. The naked face is almost black in color. The head is round and massive, the thumbs and toes well-developed, and the fingers short and thick with long pointed nails. They are diurnal and arboreal, but they do come to the ground and will walk upright using their arms to maintain balance.{4048}  

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Pithecia (saki)

Pithecia pithecia, the saki of Venezuela, Guianas, and northeast Brazil. Males are black with white to red crown, face and throat; they have a hood that does not cover the face. Females are black or brown agouti and have bright stripes that look like "smile lines" from beneath each eye to the corner of the mouth.{4048} 

Sakis are diurnal and arboreal, usually moving on all fours. They can make long leaps through the trees and have been seen running on branches on their hind legs with arms outstretched. They sometimes hang from their legs while eating. Their diet consists of berries and fruit, honey, leaves, flowers, and small mammals like bats and birds which they remove from trees and skin before eating. They are "specialist seed eaters", using their incisors and canine teeth to open tough, immature fruit to get at the softer seeds inside. They live alone or in small families. In captivity they are silent, but in the wild emit a loud and penetrating call. They appear to be "nervous and melancholy", but are reported to make affectionate pets. Although they are hunted for food and for use as pets, they do not appear to be endangered in Brazil. They are on appendix 2 of CITES.{4048} 

Saimiri are covered on their own separate page.

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©1999, Janet Becker Rodgers, DVM, MS, DipACLAM, MRCVS

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Comments? Send an email to janet.rodgers@vet.ox.ac.uk