Occurs in forest mixed with bamboo, and in varillales (large stands of thin, straight trees). Izawa (1979), Buchanan-Smith (1991a), and Ferrari et al. (1999) have indicated that it is a habitat specialist concentrating on bamboo forests and disturbed forests (secondary growth) related to their tendency to spend much of their time in the lowest parts the forest understorey in dense vegetation. They can also be found in more open, mature forest (Christen and Geissmann 1994; Christen 1998, 1999). Porter (2007) quantified the time a group spent in different habitat types during the course of a year: primary forest with dense understorey 76%; bamboo forest 10%; secondary forest 3%. The group used bamboo forest more than the sympatric tamarins (L. fuscicollis and S. labiatus). Its preference for dense vegetation is related to the extraordinary inclusion of fungi in its diet and to its insect foraging behaviour. Bamboo, stream edge, and tree falls are where they are able to find the jelly fungi and bamboo fungi that they appreciate (Pook and Pook 1981; Porter and Christen 2002; Porter, 2007; Porter et al. 2007). 

The diet of Callimico includes fruit, arthropods (especially orthopterans and stick insects), fungi, and exudates. Porter (2007; Porter and Christen 2002; see also Hanson et al. 2006) found that fungi were an essential and considerable component of the diet. Two types were eaten: jelly fungi (Auricularia, 3 species) and bamboo fungi (Ascopolyporous, 2 species). In some months (May-July, dry season) fungi accounted for 48-63% of the feeding records. Callimico forages for arthropods in the understorey and beneath the leaf litter on the forest floor. They are understorey specialists spending 84% of their time foraging below 5 m above the ground (saddleback tamarins tend to forage more a little higher, up to 10 m above the ground, and the moustached tamarins forage even higher up, mostly in the middle and lower canopy - above 10 m (Yoneda 1981; Buchanan-Smith 1999; Porter 2007)). Callimico tends to eat more vertebrates (frogs and lizards) than the tamarins. For a review see Heltne et al. (1981). 

In her long-term study of Callimico, Porter found that one group used an area of 114 ha, covering the entire home ranges of six tamarin groups (Porter 2007; Porter et al. 2007). Rehg (2003, 2007) on the other hand, found her Callimico group using a range of about 59 ha; similar in size to the Saguinus labiatus group which they travelled with for about 67% of the time. Group size was 7 (six adults and subadults and an infant). Callimico groups can be as large as 12 (Encarnación and Heymann 1998) and unlike other callitrichids can have more than one breeding female (Masataka 1981a, 1981b). Copulations occur as soon as 10 days after the female gives birth indicating post-partum oestrus. They produce single offspring. Other members of the group help carry the young (communal breeding), with the first transfer from the mother a few days (4-11) after birth. 

Callimico travels and forages with saddleback tamarins (Leontocebus fuscicollis) and moustached tamarins (Saguinus mystax, Saguinus labiatus, and Saguinus imperator) (Pook and Pook 1979a, b, 1981, 1982a). Lopes and Rehg (2003) recorded Callimico associating with S. imperator in the Serra do Divisor National Park, Brazil. Rehg (2003, 2006), Watsa et al. observed Callimico with L. fuscicollis and S. imperator at the Los Amigos Conservation Concession, Peru, from 2009-2011 (2012), and Porter (2001, 2007) studied the associations between Callimico, Saguinus labiatus, and L. fuscicollis weddelli in south-eastern Acre, Brazil, and north-western Pando, Bolivia, respectively. Porter (2007) reviews in detail the different specializations of Callimico, saddleback tamarins and moustached tamarins that allow for their sympatry.

Of the callitrichids, Callimico is the strongest leaper and has the most evident anatomical adaptations for vertical clinging and leaping between small trees, large tree trunks, and lianas at very low heights (4-5m above the forest floor) (Rylands and Mittermeier 2013).

Size:
Adult males 366 g (n=3) (Encarnación and Heymann 1998)
Adult females 355 g (n=5) (Encarnación and Heymann 1998)
These are wild specimens. In captivity, weights are rather higher: 450-600 g.

Female H&B 24.5 cm, TL 35.5 cm (n=1) (Hernández-Camacho and Barriga-Bonilla 1966)
Male H&B 19.0 cm, TL 25.5 cm (n=1) Holotype (Hernández-Camacho and Barriga-Bonilla 1966, fide Thomas)

Females reach sexual maturity at 57 weeks (median, range 48-70 weeks). Median body weight 473 g (n=10, range 420-543 g) (Dettling and Pryce 1999).

Callimico goeldii occurs in the upper Amazon from the Rio Caquetá in Colombia, south through the Peruvian Amazon and the extreme western Amazon of Brazil into the Pando region of northern Bolivia (Hernández-Camacho and Barriga-Bonilla 1966, Hernández-Camacho and Cooper 1976, Hershkovitz 1977). Hershkovitz (1977) predicted that it should occur in the Ecuadorian Amazon, but it has not been found there to date. Despite its wide range, Callimico is notoriously patchy in its distribution and is evidently absent over a large part of it.

In Colombia, it occurs from the base of the Cordillera Oriental of the Andes in the Department of Putumayo between the Ríos Putumayo and Caquetá east at least to the mouth of the Río Cahuinarí, a right bank affluent of the Caquetá. It is not known to occur in the Colombian trapezius (Hernández-Camacho and Cooper 1976; Defler 2003, 2004).

In Peru, it is evidently limited largely to the eastern Amazon. Hershkovitz (1977) mapped numerous localities south of the Río Napo, along the lower and middle Río Ucayali and the Río Tapiche. The westernmost locality given by Hershkovitz (1977, map p.864) is on the Rio Marañon, but it is listed in the gazetteer as “Apaga (Rio), enters Río Putumayo from south at approximately 4º42'S, 77º10'W, P. Soini, April 1970, sight record”. The coordinates would seem to be right, but the description of the locality wrong, and the Rio Marañon is excluded from the distribution map of Aquino and Encarnación (1994a). These authors have Callimico only definitely occurring south of the lower Ucayali (from the mouth of the Rio Blanco), extending to both sides of the Ucayali at about 6ºS and south along the Andean foothills to the Río Pachitea and the Madre de Dios. It occurs in the Manu National Park (Aquino and Encarnación 1994a, Watsa et al. 2012) and as far east within Peru as the Los Amigos Conservation Concession north of the Madre de Dios River (Watsa et al. 2012). From there it extends east into extreme northern Bolivia, north of the Río Tahuamanu (Buchanan-Smith et al. 2000, Christen and Geismann 1994, Watsa et al. 2012). Christen and Geismann (1994) reported seeing Callimico south of the Río Nareuda, indicating it occurs south as far as the Rio Muyumanu. Buchanan-Smith et al. (2000) found no evidence of its occurrence south of the Tahuamanu-Nareuda.

Callimico occurs in a small part of the south-west Brazilian Amazon in the state of Acre, through the Serra do Divisor south of the upper Rio Juruá to the Rio Gregório (state of Amazonas), to the Rio Iaco (above the Rio Acre) on the south (right) bank of the upper Purús, and into the Madeira basin along the Rio Abunã in the state of Rondônia (Hershkovitz 1977, Ferrari et al. 1999, Lopes and Rehg 2003).

The range of this species (both the extent of occurrence and area of occupancy) are suspected to be in decline, given that the species is found in four of the world's top seven countries in terms of current rates of tropical forest loss: Peru, Bolivia, Brazil and Colombia. Increased forest loss within this species' range is likely to be driven by human population expansion, road construction projects, slash-and-burn agriculture, timber harvesting and artisanal gold mining.

Less than half of the forests in which Callimico is found are protected.  Increased forest loss within this species' range is likely to be driven by human population expansion, road construction projects, slash-and-burn agriculture, timber harvesting and artisanal gold mining.

This species occurs in the following protected areas:

Brazil
Serra do Divisor National Park (846,408 ha) (Calouro 1999; Lopes and Rehg 2003)

Colombia
Amacayacu Natural National Park (293,000 ha) Within presumed range (Defler 1994, 2003, 2004)
Cahuinarí Natural National Park (575,500 ha) Within presumed range (Defler 2003, 2004)
La Paya Natural National Park (442,000 ha) (INDERENA 1989; Polanco-Ochoa et al. 1999) Within presumed range (Defler 2003, 2004).

Peru
Manu National Park (Terborgh 1983), Sierra del Divisor National Park (Vriesendorp et al. 2005, Hershkovitz 1977), Los Amigos Conservation Concession (Watsa et al. 2012), Pucacuro National Reserve (Soini 2001; Vriesendorp et al. 2006 )

Bolivia

Estaciones Biológicas de Abuná y Tahuamanu (Porter 2007; Nacimento in prep.)


It is listed on Appendix I of CITES.