Tamarin species vary considerably in appearance, ranging from nearly all black through mixtures of black, brown and white. Mustache-like facial hairs are typical for many species. Their body size ranges from (plus a tail). They weigh from . In captivity, red-bellied tamarins have been recorded living up to 20.5 years, while cotton-top tamarins can live up to 23 years old. Distribution Tamarins range from southern Central America through central South America, where they are found in northwestern Colombia, the Amazon basin, and the Guianas. Behavior and reproduction Tamarins are inhabitants of tropical rainforests and open forest areas. They are diurnal and arboreal, and run and jump quickly through the trees. Tamarins live together in groups of up to 40 members consisting of one or more families. More frequently, though, groups are composed of just three to nine members. Tamarins are omnivores, eating fruits and other plant parts as well as spiders, insects, small vertebrates and bird eggs. Gestation is typically 140 days, and births are normally twins. The adult males, subadults, and juveniles in the group assist with caring for the young, bringing them to their mother to nurse. After approximately one month the young begin to eat solid food, although they aren't fully weaned for another two to three months. They reach full maturity in their second year. Tamarins are almost exclusively polyandrous. Cottontop tamarins (Saguinus oedipus) breed cooperatively in the wild. Cronin, Kurian, and Snowdon tested eight cottontop tamarins in a series of cooperative pulling experiments. Two monkeys were put on opposite sides of a transparent apparatus containing food. Only if both monkeys pulled a handle on their side of the apparatus towards themselves at the same time would food drop down for them to obtain. The results showed that tamarins pulled the handles at a lower rate when alone with the apparatus than when in the presence of a partner. Cronin, Kurian, and Snowdon concluded from this that cottontop tamarins have a good understanding of cooperation. They suggest that cottontop tamarins have developed cooperative behaviour as a cognitive adaptation. In some locations, saddle-back tamarins (subgenus Leontocebus) live sympatrically with tamarins of the subgenus Sanguinus, but the saddle-back tamarins typically occupy lower strata of the forest than do the Sanguinus species. Saddle-back tamarins have longer and narrower hands than Sanguinus species, possibly adaption to differing foraging behavior, as saddle-back tamarins are more likely to search for insects that