Goeldi’s Monk
Taxonomy
■ Phylum: Chordata – chordates
■ Class: Mammalia – mammals
■ Order: Primates – primates
■ Family: Callitrichidae – callitrichids
■ Species: Callimico goeldii – Goeldi’s Monkey
Conservation
Distribution and habitat
Goeldi’s monkeys are found only in Bolivia, Peru, Colombia, and Brazil, with the densest populations in eastern Peru. They mainly inhabit the understorey of rainforests, where they move around at about 5 meters above the ground, jumping vertically between trees.
They live in three main habitats: rainforest understoreys, bamboo forests, and secondary forests with thick lower vegetation. Their habitat elevation ranges from 144 to 300 meters above sea level.
Adaptions
Goeldi’s monkeys are small primates with short, dense, and smooth fur on their bodies, which becomes fluffier around the neck and tail. Their coat colour is most commonly black, but it can range from silvery to dark brown, especially on the tail and upper neck.
The body length of adult Goeldi’s monkeys ranges from 210 to 230 mm, while the tail is longer, measuring between 255 and 324 mm. Adult weight varies between 393 and 860 grams, with males generally being heavier than females. They also have small claws that help them adapt to moving through dense understorey vegetation.
Diet
Goeldi’s monkeys descend to the ground or climb into the canopy in search of food. Their diet changes seasonally. During the wet season, more than half of their diet consists of fruits and insects, which they forage for on branches and beneath leaves. In the dry season, 50–65% of their diet is made up of fungi, mainly jelly fungi and bamboo fungi — they are the only primates known to have fungi as a seasonal dietary staple.
Breeding
Goeldi monkeys are usually monogamous, though sometimes polygamous, with the dominant male mating with several females. Partners are chosen within their group, and they do not change territories. Both parents are actively involved in the care of their offspring. The species typically gives birth to one offspring twice a year, with a gestation period of around 155 days. The infant’s weight is usually 30–60 grams. The first offspring is born during the rainy season, while the second one is born later in the year. After a few weeks, the entire group participates in the care of the young, which helps the females return to breeding faster. Offspring becomes independent at around 12 weeks of age. One female dominates the group, often killing the offsprings of subordinate females. Females reach sexual maturity at about one year of age, while males mature at 15–16 months.
Conservation and threats
The survival of the species is threatened by habitat loss due to human economic activities, particularly the deforestation of bamboo forests and rainforests. Due to the low population density and the species’ wide distribution range, monitoring the population is challenging. Therefore, additional research is needed to assess the impact of land use on conservation efforts.
References:
IUCN 2025. The IUCN Red List of Threatened Species. Callimico goeldi. Accessed 28.04.2025. https://www.iucnredlist.org/
UNEP (2025). The Species+ Website. Compiled by UNEP-WCMC, Cambridge, UK. Accessed 24.04.2025. https://speciesplus.net/
Maffei, D. 2025. Callimico goeldii, Animal Diversity Web. Accessed 28.04.2025. https://animaldiversity.org/accounts/Callimico_goeldii/
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