Callitrichids do not suck up liquids or hold vessels to the mouth as do most cebids and catarrhines. The faculty of suckling, a specialization of the young, disappears soon after weaning. During the dry season they are known to be less active and more social due to low food sources. Chemosignalling Marmosets and tamarins possess a rich repertoire of chemosignalling behaviors. These are associated closely with investigatory behaviors. In all species, the most conspicuous and most frequently seen chemosignalling behaviors are stereotyped scent-marking patterns involving the circumgenital and suprapubic glands, urine, and the sternal gland. Most scent marking is performed on items in the environment. In addition, marking the bodies of partners has also been reported for several species. Reproduction Tamarins live in small groups of usually four to nine individuals and have some interesting reproductive traits. They give birth to twins, and only one female (the dominant individual) breeds in any single social group. The hormones present in the dominant female's urine suppress the reproductive cycles in the subordinate females of the group. Groups are polygynandrous. Gestation averages at 140 days. Callitrichids in general are unique in the intensity of their relations to infants. The newborns may be carried from the first day by group members other than the mother (including males in the group). Weaning occurs from 9–13 weeks, when most of the food ingested is obtained through sharing or stealing. At the juvenile stage (beginning at 4–7 months) 'twin fights' may occur, especially between same-sexed twins, to determine status differences. The sub-adult stage begins at 9–14 months, and the young animal has the size and appearance of an adult. Puberty takes place at this time but the young do not reproduce. At the adult stage (beginning at 12–21 months), sexual maturity is attained. Conservation status In 2008, Leontocebus tripartitus was assessed by the IUCN Red List. This species is listed as Near Threatened in light of a projected future decline of around 25% over the course of three generations (18 years) due to anticipated high rates of deforestation. The forests where L. tripartitus occurs along the Rio Yasuni in Ecuador are remote and have, to date, suffered little impact from human activities, other than small localized encampments for petroleum prospecting. However, the occurrence of petroleum in the region, resulting in the current construction of the Pompeya-Iro highway, is reason for some concern for the future of these