Saguinus graellsi
Graells's tamarin

Saguinus graellsi, commonly known as Graell’s tamarin, is native to the upper half of the Amazon between the Napo River and the Pastaza River. It is found in Colombia, Ecuador, and Peru. (de la Torre, Di Fiore, and Stevenson, 2008; Macdonald, 1984)

The habitat of S. graellsi includes tropical rain forest, secondary forests that have regrown following a natural disturbance to the rain forest, forest patches within savanna, and along river-edge forests around Amazonian tributaries. ("New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003; Macdonald, 1984)

Graell’s tamarins have fine silky pelage and, unlike many other tamarins, are uniformly colored. The head, neck, mantle, and forelimbs are black to blackish brown. The crown is pale brown and the tail is black except for a brownish basal portion. The area surrounding the mouth has short white hairs. Infants are born with very short pelage. Adults weigh 225 to 900 g, and the length of their head and body is 175 to 310 mm. Tail length is 250 to 440 mm. Their prehensile tails are always longer than the combined length of their head and body, and their legs are longer than their arms. Graell’s tamarins have claw-like nails on all digits with the exception of the hallux, which has a flat nail. The hallux is opposable, but the pollex is not. On each side of the upper and lower jaws there are two incisors, one canine, three premolars, and two molars, which gives them a total of 32 teeth. Saguinus graellsi is considered a long-tusked callitrichid because the canines are longer than the incisors. Moderate sexual dimorphism exists within this species, with females larger than males. (Macdonald, 1984; Nowak, 1999)

In the wild, the lifespan of S. graellsi is unknown, but in captivity they have lived 7 to 16 years. (Macdonald, 1984)

Graell’s tamarins live in groups of five to ten individuals. Sometimes two or three social groups join together to form large group of ten to twenty, usually staying together for less than a day. They are diurnal, generally leaving their sleeping areas at dawn. Social behavior among the group includes grooming during times of rest. The majority of the time social grooming focuses on the breeding female and does not include the young, who play together during this time by chasing, wrestling, and playful biting. Grooming is initiated when one individual lies down in front of another tamarin with a specific body posture. Mass huddling during resting periods is also common. Aggression between group members is rare. When an aggressive interaction does occur, it is usually in response to limited food resources and consists only of threats and displacements - fighting is extremely rare in the wild. ("New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003; Macdonald, 1984; Nowak, 1999)

Home Range

Groups move between 1,000 and 2,000 m per day. ("New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003)

Graell’s tamarins make a long call audible to humans that travels 150 to 200 m, made up of 2 to 30 notes. The call is different between species, populations, and individuals. Within a group, the construction of the long call may reflect social status. Calls function to keep the social group together and to regulate space between neighboring groups. Graell’s tamarins also have many other calls, including alarm calls when a group member sees a raptorial bird, squawking calls amongst young when seeking food from group members, and harsh atonal calls to communicate aggression. Infants chatter and use calls incorrectly, seeming to learn from group members as they age. Olfaction is another important component of communication. Scent glands are found around the genitals (anogenital or circumgenital glands), lower abdomen (suprapubic glands), and sternum (sternal gland). The glandular secretions, a mixture of fatty acids, esters, proteins, and other organic compounds, communicates information about species, sex, reproductive state, and individual identity. The secretion may be mixed with urine and applied to aspects of the environment (branches, trunks, and lianas) with habitual rubbing motions. Depending on the secretion, it is called anogenital, suprapubic, or sternal scent marking. Adult females scent mark more than adult males. Graell’s tamarins also use physical signals of communication. Arousal is signified by raised hair on the head, ears, shoulders, or whole body. Facial expressions denoting aggression include frowning, opening of the mouth, and shaking of the head. ("New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003; Nowak, 1999)

All males and one-third of females have dichromatic vision; remaining females have trichromatic vision. While the gene for short wavelength vision is not sex-linked, the genes for medium and long wavelength vision are recessive and located on the X chromosome. It is believed that dichromatic vision enables better detection of camouflaged prey and predators, while trichromatic vision enables better detection of ripe, colorful fruits. ("New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003; Macdonald, 1984; Nowak, 1999)

Graell’s tamarins spend 25% to 30% of their active time searching for food. Primarily frugivores, they feed on fruits, flowers, nectar, plant exudates, insects, and small vertebrates. When available, small sweet fruits make up the majority of their diet, especially those from the genera Pourouma, Ficus, Cecropia, Inga, and Miconia. Plant exudates like sap, gums, and resin are also eaten, though unlike short-tusked callitrichids, the long-tusked S. graellsi is unable to gouge trees to stimulate the flow of exudate. They consume exudates available through holes bored by insects or from wind damage. During seasonal fruit shortages, Graell’s tamarins increase their intake of nectar and gum to compensate. Animal prey includes frogs, snails, lizards, and insects - particularly grasshoppers, beetles, and stick insects. They also eat baby birds and probably eggs. ("New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003; Macdonald, 1984; Nowak, 1999)

Predators include raptorial birds such as Guianan crested eagles, ornate hawk eagles, and bicolored hawks, snakes such as anacondas, rainbow boas, and jararacas, and tayras. Ocelots may also be predators of tamarins – tamarin hairs have been found in their feces. The response of Saguinus graellsi to predators includes alarm calling, escaping, and hiding. If caught in a tree without anywhere to hide, Graell’s tamarins may drop suddenly to the ground. Once a predator is detected, group members often surround and harass it while emitting specific vocalizations. At least one group member is constantly on guard to prevent surprise attacks by predators and they sleep surrounded by thick foliage to camouflage themselves. ("New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003; Macdonald, 1984)

Graell's tamarins play an important role in seed dispersal. They swallow seeds up to 1.5 cm long and pass them through their digestive tract in 1 to 3 hours, depositing them away from parent plant. Their digestive processes don’t harm the seeds. Though they appear to swallow the seeds because it is difficult to separate the fruit pulp from them, it has been suggested that swallowing such large seeds helps dislodge intestinal parasites. (Garber and Kitron, 1997; Macdonald, 1984)

Although believed until the 1970's to be carriers of malaria and yellow fever, S. graellsi probably do no harm to humans. (Macdonald, 1984)

Humans benefit from the seed-dispersing ecosystem role of S. graellsi. (Garber and Kitron, 1997; Macdonald, 1984)

In 2008, the IUCN Red List considered S. graellsi near threatened, stating that the species almost qualifies as threatened and its population is continuing to decline. The severe deforestation of its western Amazon home is considered the cause of this diminishing population. The IUCN estimates that over the next three generations, approximately 18 years, population size will decrease 20% to 25%. Graell’s tamarins were previously considered a subspecies of black-mantled tamarins (Saguinus nigricollis). In 2003, Graell’s black-mantle tamarins (Saguinus nigricollis graellsi) were rated “least concern” on the list. CITES does not list Saguinus graellsi in its appendices (as a separate species or as a subspecies of Saguinus nigricollis) as a trade-restricted species. ("Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)", 2008; "New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003)

Saguinus graellsi was previously recognized as a subspecies of Saguinus nigricollis, S. n. graellsi. ("New World monkeys II: Marmosets, tamarins, and Goeldi's monkey (Callitrichidae)", 2003; Macdonald, 1984; Nowak, 1999)