By Rhonda Garza
Geographic Range
Silvery marmosets, Callithrix argentata, are found south and east of the Amazon River in eastern Brazil. Silvery marmosets are isolated from other marmosets, except south of the Amazon delta where they co-occur with common marmosets, Callithrix jacchus. (Preston-Mafham 1992)
Biogeographic Regions:
neotropical 
(native ).
Habitat
Within the tropical rain forest silvery marmosets take advantage of tree hollows, dense vegetation, and vine tangles for sleeping sites.
(Rowe 1996)
Terrestrial Biomes:
rainforest .
Physical Description
(47.87 oz)
About the size of a squirrel, silvery marmosets are one of the smallest New World monkeys. Head and body length averages 21.59 cm and tail length averages 29.21 cm. Silvery marmosets vary in color from silvery white to dark brown. Dark brown marmosets have hairless ears and faces and are sometimes referred to as bare-ear marmosets. Because of their dark tails, silvery marmosets are also referred to as black-tailed monkeys. A unique feature of the silvery marmoset is that their jaw narrows to a sharp point. This pointed jaw, along with short canine teeth, are believed to be an adaption for their unique feeding habit. While other New World monkeys posess nails on all of their toes, marmosets have claws on all of their toes except the big toe. (Preston-Mafham 1992; Napier 1985)
Some key physical features:
endothermic ; bilateral symmetry .
Reproduction
Silvery marmosets breed twice a year.
Females usually give birth to twins twice a year after a gestation time of 145 days. Ten to twenty days after giving birth females ovulate, at the same time they are nursing current young. Subordinate females within the family group are prevented from ovulating by exposure to pheromones released by dominant females.(Napier 1985)
Key reproductive features:
iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous .
Silvery marmosets live in extended families of about twelve where all the members help care for the young. Silvery marmoset fathers carry their infants and return them to the mother to be fed every two to three hours. Infants are weaned from their mother's milk at about six months and are considered adults at one to two years old.
Parental investment:
pre-fertilization (provisioning, protecting: female); pre-hatching/birth (provisioning: female, protecting: female); pre-weaning/fledging (provisioning: female, protecting: male).
Behavior
Silvery marmosets are arboreal and diurnal. Their long, curved claws enable them to climb trees and escape predators. Both males and females engage in scent marking to claim territories and communicate with others. They also communicate vocally when excited, alarmed, or at play.
When confronted with a possible threat, silvery marmosets will lower their eyebrows and smack their lips.
(Swindler 1998; Rowe 1996)
Key behaviors:
arboreal ; scansorial; diurnal ; motile ; territorial ; social ; dominance hierarchies .
Food Habits
Silvery marmosets are gumivores, their diet consists mainly of the sap and gum of trees. With canines and incisors of equal length they are able to gouge holes in trees and lap up the exudate. They supplement their diet with fruit, insects, and leaves. (Swindler 1998)
Primary Diet:
herbivore (eats sap or other plant foods).
Animal Foods:
insects.
Plant Foods:
leaves; fruit; sap or other plant fluids.
Economic Importance for Humans: Negative
By feeding on newly planted crops that replace rain forests silvery marmosets have become pests. As a result humans in these areas carry out active extermination campaigns.
(Preston-Mafham 1992)
Economic Importance for Humans: Positive
Because of their small size and mild disposition marmosets are used regularly in medical research. Studying the fertilization, placental development, and embryonic stem cells of marmosets may reveal causes of developmental problems and genetic disorders in humans. (WRPRC, 1997)
Conservation Status
IUCN Red List: [link]:
Least Concern.
US Federal List: [link]:
No special status.
CITES: [link]:
Appendix II.
The destruction of forests has resulted in the endangerment of many rainforest animals, including many monkey species. However, silvery marmosets have been able to survive by taking advantage of human food crops and living in secondary forest habitats. It remains to be seen whether this trend continues.
(Preston-Mafham 1992)
Contributors
Rhonda Garza (author), Fresno City College.
Carl Johansson (editor), Fresno City College.
