The pygmy marmoset (Cebuella pygmaea) is the smallest monkey species in the world and is native to the rainforests of South America. Here’s a description of its distribution by country:

1. Brazil: Pygmy marmosets are found in various regions of Brazil, particularly in the Amazon rainforest and adjacent areas. They inhabit dense tropical forests, including both lowland and montane forests, in states such as Amazonas, Acre, Rondônia, and Pará.
2. Peru: Pygmy marmosets are also native to Peru, where they inhabit rainforests in the Amazon basin, particularly in the eastern regions of the country. They are found in departments such as Loreto, Ucayali, and Madre de Dios.
3. Colombia: Pygmy marmosets are present in certain parts of Colombia, particularly in the Amazon region and the foothills of the Andes mountains. They inhabit tropical forests in departments such as Amazonas, Caquetá, and Putumayo.
4. Ecuador: Pygmy marmosets are also found in Ecuador, where they inhabit the Amazon rainforest in the eastern part of the country, particularly in provinces such as Sucumbíos, Orellana, and Pastaza.

Pygmy marmosets are arboreal primates, meaning they spend most of their time in trees, where they forage for insects, fruits, and tree sap. They have a specialized diet and a high metabolism, allowing them to extract nutrients from a variety of food sources. Despite their small size, pygmy marmosets are social animals, living in family groups consisting of a breeding pair and their offspring.

While pygmy marmosets are not considered endangered, they face threats from habitat loss due to deforestation, as well as capture for the illegal pet trade. Conservation efforts are underway to protect their habitats and regulate trade to ensure the sustainability of wild populations.