Callithrix aurita and C. flaviceps are the southernmost forms of marmosets in terms of the natural range of the genus (C. jacchus, C. penicillata and C. geoffroyi have been introduced further south in Paraná, São Paulo, Santa Catarina and Argentina). They occur in the montane Atlantic coastal forest and forests of the inland plateau, at altitudes up to 1,200 m where dry season temperatures can fall close to freezing (Ferrari et al. 1996). They show a preference for disturbed forest, being rare in old growth forest with sparse understoreys (Ferrari 1988; Ferrari and Mendes 1991). There is a natural hybrid zone, with Callithrix aurita, at the Serra do Brigadeiro, Carangola, in south-eastern Minas Gerais (Coimbra-Filho et al. 1993; Cosenza 1993; Mendes 1997a; Cosenza and Melo 1998).

Marmosets and tamarins are distinguished from the other monkeys of the New World by their small size, modified claws rather than nails on all digits except the big toe, the presence of two as opposed to three molar teeth in either side of each jaw, and by the occurrence of twin births. They eat fruits, flowers, nectar, plant exudates (gums, saps, latex), fungi and animal prey (including frogs, snails, lizards, spiders and insects) (see Ferrari 1988, 1991; Corrêa et al. 2000; Hilário and Ferrari 2010a). Marmosets have morphological and behavioural adaptations for gouging trees trunks, branches and vines of certain species to stimulate the flow of gum, which they eat, and in some species form a notable component of their diet (Coimbra-Filho 1972; Rylands 1984). Nevertheless, C. flaviceps rarely gouge trees in order to stimulate exudate production and feed primarily on exudates already available in the environment (Ferrari 1991; Hilário and Ferrari 2010a). They live in extended family groups of 3 to 20 individuals (Alves 1986; Ferrari 1991; Ferrari and Digby 1996; Guimarães 1998; Hilário and Ferrari 2010a). Reproduction is concentrated at one dominant female, although up to four females can reproduce simultaneously in on group (Ferrari 1991; Guiarães 1998; Hilário and Ferrari 2010b). C. flaviceps groups present weak territoriality and occupy large home ranges (33.9 -138.3 ha) compared to other congeneric species (Ferrari 1991; Guiarães 1998; Hilário 2009).

The ecology and behaviour of C. flaviceps has been studied by Ferrari (1988, 1991, Ferrari and Diego 1992) at the 880 ha Caratinga Biological Station in Minas Gerais. The home range of the group he studied was 35.5 ha. Guimarães (1998a, 1998b) also studied the same marmoset group at Caratinga. Latter, Hilário (2009, Hilário and Ferrari 2010a) studied the ecology and behavior of a free ranging group at the Augusto Ruschi Biological Reserve (3,589 ha) in Espírito Santo.

The dentition of Callithrix flaviceps is less specialized for tree-gouging to obtain gum than it is in C. jacchus and C. penicillata (see Natori 1986). Nevertheless, at Caratinga Biological Station gum is an important part of the diet year round, and largely obtained from sites where it is available without requiring gouging (Ferrari 1988, 1991; Ferrari et al. 1996). At Augusto Ruschi Biological Reserve, however, C. flaviceps feeds predominantly on fungi and small animals, with gum representing only 3% of the group’s diet (Hilário and Ferrari 2010a).

Size:
Average weight: 406 g (Rosenberger 1992).

The distribution of Callithrix flaviceps is described by Hershkovitz (1977), Coimbra-Filho et al. (1981), and Coimbra-Filho (1986a). It occurs in the Serra da Mantiqueira in southern Espírito Santo, south of the Rio Doce at least to the state boundary with Rio de Janeiro (and in the past possibly in the north of the state of Rio de Janeiro, in the municipalities of Natividade, Porciuncula and the north of Bom Jesus do Itabapoãna when they were forested). It extends west into eastern Minas Gerais in scattered localities in the highly fragmented forests of the Rio Manhuaçu basin as far as Manhuaçú (40°02’W), as noted by Coimbra-Filho (1986a) Coimbra-Filho et al. (1981) and Mendes and Melo (2007). Ferrari and Mendes (1991) and Mendes (1993) reviewed the distribution of C. flaviceps. Hirsch (2003) obtained records in Minas Gerais which have extended its known range somewhat north and west, towards the east (right bank) of the Rio Doce (Fazenda Saet [19º43'S, 42º26'] and the Fazenda do Eraldo A. Alves [19º45'S, 42º25'] both at an altitiude of 270 m and about 10 km from the east bank of the Rio Doce, in the municipality of Pingo d’Água). Hirsch (2003) also refers to two localities which would extend the range a little further south in Minas Gerais, but they have still to be confirmed and may be hybrids with C. aurita (the left bank of the Rio Matipó, municipality of Abre Campo, and the Córrego Jurumirim, left bank of the Rio Casca, municipality of Rio Casca).

In 2011 an individual of C. flaviceps was collected at the municipality of Varre-Sai, in the northernmost part of the state of Rio de Janeiro. However, a larger investigation is necessary to confirm the presence of the species in this state (Oliveira and Grelle 2012).

It is suspected that both extent of occurrence and area of occupancy for this species are in decline due habitat degradation.

This species occurs in the following protected areas:

Minas Gerais
Caparaó National Park (31,853 ha) (part Espírito Santo)
Caratinga Biological Station / RPPN Feliciano Miguel Abdala (900 ha) (Coimbra-Filho et al. 1981).
RPPN Mata do Sossego Biological Station (221 ha) (privately owned)

Espírito Santo
Augusto Ruschi Biological Reserve (4,492 ha) (Pinto et al. 1993)
Pedra Azul State Reserve (993 ha) (Mendes 1991; Ferrari and Mendes 1991; Oliver and Santos 1991)
Forno Grande State Reserve (340 ha) (Mendes 1991; Ferrari and Mendes 1991; Oliver and Santos 1991)
São Lourenço Biological Station (Mendes 1991; Ferrari and Mendes 1991; Oliver and Santos 1991)
Santa Lucia Biological Station (350 ha) (Mendes 1991; Ferrari and Mendes 1991; Oliver and Santos 1991)
Montes Verdes Florest Reserve (1500 ha)(privately owned) (Mendes 1991).

Attempts to establish a captive breeding program have to date been unsuccessful (Coimbra-Filho et al. 1997).

It is listed on Appendix I of CITES.