New records for Callithrix aurita and Callithrix hybrids in the region of Viçosa, Minas Gerais, Brazil

The genus Callithrix includes six species distributed across eastern Brazil in the Atlantic Rainforest, Caatinga, and Cerrado biomes. The buffy-tufted-ear marmoset (Callithrix aurita) is endemic to the Atlantic Rainforest and occurs in the states of Minas Gerais, Rio de Janeiro, and São Paulo. This species is considered ‘Endangered’ and listed among the world’s 25 most threatened primates. The release into the wild of marmosets kept as pets has led to numerous invasive populations in southeastern Brazil, which hybridize with native congeneric species. This, combined with habitat loss and fragmentation, has caused a dramatic decline in C. aurita populations, and threatens them with extinction. The city of Viçosa, in Minas Gerais, has an almost 50-year history of introduced Callithrix species. C. aurita, the native species, was last recorded in the region in 1995. With the aim of updating knowledge on the current situation of Callithrix in the region, we surveyed 43 fragments of the Atlantic Forest in Viçosa and nearby cities between 2017 and 2019. We recorded 22 groups of hybrid forms, three solitary individuals of hybrid marmosets, two mixed groups of C. aurita with hybrids, and a single group of C. aurita. This record of C. aurita was the first of a pure group of the species in the region in 20 years. These results highlight one of the most important threats to C. aurita, and management actions are urgently needed to control invasive and hybrid populations, to allow the endangered buffy-tufted-ear marmoset to recover