Goeldi's marmosets are small, South American New World monkeys. They are blackish or blackish-brown in color and the hair on their head and tail sometimes has red, white, or silvery brown highlights. The species takes its name from its discoverer, the Swiss naturalist Emil August Goeldi.
Goeldi's marmosets live in the upper Amazon basin region of Bolivia, Brazil, Colombia, Ecuador, and Peru. They inhabit tropical moist forests that have patchy canopy cover and dense shrubby undergrowth.
Goeldi's marmosets live in small social groups that consist of approximately six individuals. These groups stay within a few feet of one another most of the time, staying in contact via high-pitched calls. They also use scent, facial, and body language in order to communicate with each other. Goeldi's marmosets are excellent climbers and leapers. They easily leap from one tree to another, turn in flight, and grab their target. These marmosets are diurnal and prefer to forage in dense scrubby undergrowth; perhaps because of this, they are rarely seen and groups live in separate patches of suitable habitat, separated by miles of unsuitable flora.
Goeldi's marmosets are omnivores. In the wet season, their diet includes fruit, insects, spiders, lizards, frogs, and snakes. In the dry season, they feed on fungi, the only tropical primates known to depend on this source of food.
Little is known about the mating system in Goeldi's marmosets. Females give birth twice a year and carry a single infant per pregnancy. The gestation period lasts from 140 to 180 days. For the first 2-3 weeks the mother acts as the primary caregiver until the father takes over most of the responsibilities except for nursing. The infant is weaned after about 65 days. Females in this species reach reproductive maturity at 8.5 months of age, males at 16.5 months.
There are no major threats to Goeldi's marmosets at present. However, the loss of their habitat can become a threat in the future due to logging and different development projects.
The IUCN Red List and other sources don’t provide the number of the Goeldi's marmoset total population size. Currently, this species is classified as Vulnerable (VU) on the IUCN Red List and its numbers today are decreasing.