Tamarins are one of 16 species of small New World monkeys grouped in two genera: Leontopithecus and Saguinus. They belong to the subfamily Callitrichinae, which also includes their smaller counterparts, the marmosets (Callithrix, Cebuella, and Mico) and Goeldi’s monkeys (Callimico). Callitrichines are the smallest monkeys in the world, with bodies ranging between 20-30 centimeters in length with a tail of 30M0 centimeters. They have thick fur, which makes them look deceptively larger than their actual body size. In addition, many are brightly colored and have distinguishing manes, tufts, and moustaches. Callitrichines are unlike other New World monkeys in several features: they do not have prehensile tails, they lack a third molar (except Callimico), and they regularly have twin offspring (except Callimico). Callitrichines were once considered the most ancestral New World monkeys because of their small body size and derived claws (instead of nails). However, these traits are more likely derived specializations related to adaptations for insectivore and exudate (gum and sap) feeding rather than signs of primitiveness.
Tamarins are found in the tropical regions of South America and Panama. They are diurnal, arboreal, quadrupedal, and feed on plants, insects, and exudates. Tamarins are unable to gouge holes in tree bark to stimulate the flow of exudates. Instead, they exploit exudates found at holes previously gnawed by sympatric marmosets or holes made by wind and insects. Tamarins use their derived claws to cling to tree trunks while feeding on saps and gums and for searching for insects hidden in tree bark.
Tamarins exhibit variable social organization and have been found in polygynous, monogamous, and polyandrous groups mostly composed of recently dispersed, unrelated individuals. In polyandrous groups, there is often one breeding adult female and more than one breeding adult male. It is thought that male tamarins allow other males reproductive access to the female because the survival rate of offspring raised by two fathers is higher than the survival rate of offspring raised by one. Adult males and other group members play an active role in raising the young, which is necessary since female tamarins often give birth to twins. By having group members help carry the infants, females do not expend unnecessary energy transporting them. This also allows females to forage unimpeded. In addition, healthier females are able to produce more offspring at more frequent intervals. In tamarin groups in which there is more than one adult female, the subordinate females’ reproductive capabilities are often hormonally suppressed by the dominant female. This means that even though there may be more than one adult female capable of breeding in a tamarin group, usually only the dominant female produces offspring.
At least three species of tamarin are considered critically endangered: the black-faced lion tamarin (L. caissara), the black lion tamarin (L. chrysopygus), and the golden lion tamarin (L. rosalia). The latter is most known for a successful captive breeding program and reintroduction into the forests of Brazil when it was on the brink of extinction.
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