A very small tree-climbing monkey of the upper Amazon basin.
Orange-brown fur covers the body; long surrounding hair hides the ears. Its fingernails are claw-like.
Beginning in 1996, researchers recorded the feeding of 34 pygmy marmoset groups in 11 populations in Ecuador's Amazon. Across those sites, they documented 20 plant species used for exudates—18 trees and two lianas—and the mix varied by population. At San Pablo, selective logging reduced the abundance of preferred food plants; the marmosets then began using other plants that had not previously been recorded in their diet.
The same chapter reported that 16 of the 34 groups could no longer be found after searches of their population areas. Selective logging had affected the home ranges of several missing groups, leading the authors to consider death more likely than long-distance dispersal. Diet flexibility and forest loss were both recorded in the same study.
IUCN Red List (IUCN SSC Primate Specialist Group) · Vulnerable (VU) · Global
The latest global IUCN listing is Vulnerable (VU) in the 2025 Red List. The exact assessment date could not be verified. The preceding detailed assessment, published in amended form in 2021 and assessed on 26 January 2015, estimated a decline of more than 30% across three generations beginning in 2009. It linked the decline to continued loss and degradation of habitat, including deforestation, mining, oil palm cultivation and settlements, as well as hunting.