Saving the world’s smallest monkeys from extinction

Surveying the world’s rarest marmoset

Rodrigo Salles de Carvalho

Programa de Educação Ambiental – PREA

The loss and fragmentation of natural habitats is one of the main causes of the extinction of species. In Brazil, one of the most diverse countries on the planet, the Atlantic Forest biome stands out as a global biodiversity hotspot, harboring unique species. The buffy-headed marmoset (Callithrix flaviceps), a small primate endemic to this biome, deserves special attention as it has the smallest range in the genus Callithrix. Its habitat has been highly degraded by human activity, but it also suffers from the presence of invasive species of marmosets, leading to interspecific competition and hybridization.

The buffy-headed marmoset is now classified as Critically Endangered (CR) by the IUCN Red List and in 2022, the species joined the list of the 25 most endangered primate species on the planet (Primates in Peril). There has been no comprehensive survey of this marmoset’s distribution for many years, and so work to rapidly locate both pure groups of C. flaviceps, and invasive marmosets in its range, is urgently needed to establish key areas for protection. The survey will be carried out by Rodrigo Salles de Carvalho and the Mountain Marmoset Conservation Program (https://www.mountainmarmosetsconservation.com/about-mmcp).

The buffy-headed marmoset is one of two endangered species included in the Mountain Marmoset Conservation Program – MMCP, which integrates the work of researchers and institutions for the conservation of the species. The MMCP is part of the Brazilian National Action Plan for the Conservation of the Atlantic Forest Primates and the Maned Sloth (PAN-PPMA/ICMBio).

Goal

To carry out a rapid survey to obtain a clear and up-to-date view of where the remaining groups of C. flaviceps are, and how invasive marmosets are distributed across their range.

Methods

Geographic area

The target areas are the mountainous regions of the southwest of Espírito Santo state and a small part of eastern Minas Gerais, in scattered localities in the highly fragmented forests of the Rio Manhuaçu basin (see map).

We will survey forest fragments across the range of C. flaviceps, mapping its presence and absence as well as that of invasive marmoset species.

Rapid survey methods

We will visit a predefined sample of forest fragments, walking from dawn to dusk along transects and along the borders of the fragments. We will play recordings of the marmosets’ vocalization every 500 m, waiting for any response, and note presence or absence of native and/or invasive marmosets.

We expect to cover 5 different areas exploring approximately 10 trails measuring around 12 km each resulting in a total of 1000 georeferenced survey points.

Community conservation approaches

We will talk to local people about the marmosets, finding out if they are provisioned and their memories of the historical occurrence of the species in the area. We will also establish a network of local monitors who can report back information about their local population of marmosets. This will be key to any future rescue and translocations that may need to be carried out. Making contact with local authorities to highlight the issues facing the species survival in the area will also be important.

Outcomes

  • Up to date map of locations of remaining populations of C. flaviceps and of the presence of invasive marmosets over its range.
  • Inclusion of this data in the dataset of the Mountain Marmosets Conservation Program.
  • Community monitoring network established.