Simia jacchus Linnaeus, 1758, Pernambuco, Brazil. OTHER COMMON NAMES
French: Ouistiti a toupet blanc; German: Weisspinselaffe; Portuguese: Sagui-do-nordeste.
Average weight: 11.3 oz (320 g); head and body length: 7.3-9.8 in (18.5-25 cm); tail length: 11.6-13.8 in (29.5-35 cm). They display prominent white ear tufts.
Northeastern Brazil; introduced in eastern and southeastern Brazil.
Coastal forest, gallery forest, forest patches in open Caatinga and Cerrado bush land.
Group size ranges between 3-15, with usually several adults of both sexes plus immature individuals. Home-range size is 1.2-16.1 acres (0.5-6.5 ha), daily path length is 0.3-0.6 mi (0.5-1 km). Home range overlap with neighboring groups is variable. Encounters between neighboring groups are frequent, usually initiated by long calling. Most interactions between members from different groups are hostile, involving chasing and genital displays, but copulations between members from different groups have also been observed during these encounters. Within-group social relations are highly affiliative. Grooming is the major social activity, and breeding adults are most frequently involved in grooming interactions. Aggression
H Callithrixjacchus H Callithrix flaviceps H Cebuella pygmaea between group members is rare in the wild and usually occurs only during feeding in exudates trees. In the dominance hierarchy, the breeding adults are at the top, and the non-breeding group members are arranged according to age with older individuals ranking higher than younger ones.
Common marmosets feed primarily on exudates and insects; eating only a little fruit and occasionally small vertebrates. Exudate flow is stimulated through gouging into the tree bark.
They usually breed in monogamous pairs, but breeding by two females in the same group is quite common in the wild. Genetic data suggest that only one male breeds in a group. Despite observation of copulations between males and females from different groups, no infants seem to be fathered by extra-group males. Estrus cycle duration is 28-29 days, and gestation length is 141-146 days. In captivity, subordinate females do not show an estrus cycle. Two births per year are common both in captivity and in the wild. When two females are breeding simultaneously in the group, rearing success is lower in the subordinate female; even killing of subordinate female infants by the dominant female has been observed in a wild population. Adult males and other group members participate in infant carrying.
SIGNIFICANCE TO HUMANS
One of the most widely used laboratory primates; also kept as pets. They have been introduced to areas outside their natural range. ♦
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