Most of the available information on the ecology and behaviour of Cacajao calvus is limited to studies carried out during the 1980s (Ayres 1986, 1989), mainly at the Mamirauá SDR. This species was initially considered a habitat specialist limited primarily to the white-water flooded habitats – várzea forests (Ayres 1986, Barnett and Brandon-Jones 1997). However, new records of C. calvus in the Jutaí River – a black water river – show that the populations from the south bank of the Solimões River may be exposed to a greater variety of habitats than the populations from the Mamirauá SDR.

Like other members of the Pitheciinae family, Cacajao has morphological adaptations in their mandibular muscles, as well as in their dentition, allowing the predation of seeds found in hard-shelled fruits that are usually consumed at an immature stage (Barnett et al. 2013). Thus, seeds and fruits are the main food items in the diet of C. calvus. They can be considered frugivorous specialised in immature seeds (Ayres 1986, Barnett et al. 2013).

The groups are large, sometimes with more than 50 members. There are social subunits, or subgroups, operating in a fission-fusion system, which is a characteristic of the genus Cacajao (Ayres 1986, Bowler and Bodmer 2009). But there have been few studies focusing on this social dynamics, and other aspects of the social system of Cacajao (Bowler and Bodmer, 2009). The seasonal variation in the abundance of key resources (Ayres 1986, Bowler and Bodmer, 2011) may be an important selective pressure shaping the social system of C. calvus (Bowler et al. 2012). The main group studied by Ayres (1986) was composed of 45 individuals, who often split into foraging subunits; larger units were found during the flooding season, when there was a greater availability of fruits.

Cacajao calvus is endemic to the Amazon Rainforest, in the Amazonas State, Brazil. The species has a disjunct distribution, occurring on opposite sides of the Solimões River (Silva et al. 2021, 2024). Cacajao calvus is present in the confluence of the Solimões and Japurá rivers, almost entirely inside the Mamirauá Sustainable Development Reserve (Mamirauá SDR) (Ayres 1986, Hershkovitz 1987, Vieira et al. 2008, Silva Jr et al. 2013, Cardoso et al. 2014, Silva et al. 2021). In this region, the species is limited by the Auatí-Paraná on the north, while the Paraná do Maiana channel and Paraná do Aiupiá channel are the western limit – where the species forms a contact zone with C. rubicundus (Vieira et al. 2008). This area was estimated at 11,403 km² (Silva et al. 2021).

On the southern bank of the Solimões River, C. calvus occurs mostly in the lowland forests of the Jutaí-Riozinho interfluve (Silva et al. 2021, 2024). The species was also recorded on the western bank of the lower Juruá River in the proximities of Paraná Breu and Breuzinho – tributaries of the Juruá River (Cardoso et al. 2014). The geographic range of these populations was estimated at 16,780 km².

White uakaris were recorded in the Jurupari River – a tributary of the Tarauacá River (Silva Jr. & Martins, 1999) and in the Pauini River – a left-bank tributary of the Purus River (Sampaio et al. 2018). These populations, however, were considered as a different species, Cacajao amuna (Silva et al. 2022).

This species is listed in CITES Appendix I.

The species is officially protected in Brazil, and the major strategy applied is the National System of Protected Areas (SNUC). Most of the geographic range of Cacajao calvus on the north bank of the Solimões River is protected by Mamirauá SDR - Ramsar site no. 623. On the southern bank, the species occur in the Jutaí River Extractive Reserve (Jutaí RER) and at the Uacari Sustainable Development Reserve (Uacari SDR. While the Jutaí RER is a Federal Protected Area, the Mamirauá and Uacari SDRs are both under Amazonas State jurisdiction.