options: either find another group or stay in the natal group. In the latter case, the daughter may someday become the dominant female, or she may cease to ovulate. Daughters may compete for the role of dominant female with their siblings. Subordinate members do not generally engage in sexual reproduction. All adult black-handed tamarin participate in raising and caring for the young, including non-reproductive members of the group (which may number 2-20 members). Group members coordinate and work together to find sufficient food items for infants and juveniles. Unlike many primate groups that provide juveniles with small amounts of food, this species has a cooperative breeding system that shares a substantial portion of food with the juveniles. When group size is large, the breeding male often spends less time attending to his own young because of the universal group effort. When there is sufficient food, or if the dominant female is close to the end of her reproductive cycle, multiple females may be allowed to reproduce in a group. A number of mating variations have been observed: monogamy, polygyny, polyandry, or polygynandy. Lifetime reproduction Ovulation in female tamarins typically occurs between 12 and 17 months of age, whereas in male tamarins, sperm production occurs slightly later at about 13 to 18 months. The birth of infants has been observed in both early January and mid July. Black-handed tamarins (like all other Callitrichids) usually produce fraternal twins, but litters may consist of 2-4 infants. Triplets and quadruplets usually only occur in captivity. The growth of infants is very rapid; infants become independent within five months. Female callitrichids are able to conceive again after 2–4 weeks of giving birth to their previous offspring. Conservation The black-handed tamarin is classified as Vulnerable by the IUCN as a result of a 30% decrease in population size over the last 18 years, and is likely to become endangered if conservation measures are not taken. Because the major threat to the species appears to be a loss of suitable habitat, habitat conservation is thought to be key in their survival. The range of the black-handed tamarin is within one of the most densely inhabited areas of Brazil, where logging has removed a significant amount of the original forest, causing a decrease in food availability and refuges from predators. However, black-handed tamarins are adaptable foragers that can make use of primary, secondary and logged forests, which increases