The biology and ecology of Inia are strongly related to the seasonal variation in water levels (Martin and da Silva 2004b, Martin et al. 2004, Gómez-Salazar et al. 2012b). Their physical adaptations allow them to swim into the flooded forests in the high-water season (Layne 1958, Best and da Silva 1989a) in search of prey among the roots and trunks of partially submerged trees (da Silva 1984). Mark/recapture studies have shown that some individuals are resident to specific areas year-round (Martin and da Silva 2004a, Gómez-Salazar et al. 2011), whereas others move several tens to hundreds of kilometres within the rivers, but there does not appear to be any seasonal migration as such (Martin and da Silva 2004a).

The use of habitat by Inia is affected by the water level for all age classes, however habitat preferences differ among age and sex classes (Martin and da Silva 2004b, Mintzer et al. 2016). Sexual segregation is common; females with dependent calves spend more time inside the flooded forest and in lakes and small tributaries during the high-water season, while most adult males at any one time occur in the main rivers. The preference of nursing females for lake systems is likely due to factors favourable to calves, such as low current, abundance of small fish, and protection against predation such as by large sharks (Martin and da Silva 2004b). The predominant presence of mother-calf pairs and juveniles in lakes has been observed in much of the species’ range (Trujillo 1997, McGuire and Winemiller 1998, Denkinger 2001). Also, Mintzer et al. (2016) proposed that bays are important habitat for early life stages due to the high productivity, low current, and availability of ample water during the low-water season. Genetic analyses of control region mitochondrial DNA and microsatellites of samples obtained from the Mamirauá Reserve suggested that females have a restricted distribution while males mediate gene flow among groups (Hollatz et al. 2011).

During the low-water season, Inia are often concentrated below channel confluences (Best and da Silva 1989a,b, Leatherwood 1996, Vidal et al. 1997, McGuire and Winemiller 1998, Leatherwood et al. 2000). In the main rivers they occur most often within 150 m of the banks, with lower densities in the centre of large rivers (Martin et al. 2004a, Gómez-Salazar et al. 2012a). As the water starts rising, their affinity for confluences diminishes, probably because the animals move into appended lakes and flooded forests (Leatherwood et al. 2000, Aliaga-Rossel 2002, Martin and da Silva 2004a,b) which become more important habitats during the high-water season due to their high productivity and prey diversity (Martin and da Silva 2004b). When the water is receding, dolphins leave the lakes and the shallow habitats, perhaps in order to avoid getting trapped (Martin and da Silva 2004a,b, Mintzer et al. 2016).

Due to intense intraspecific interactions, Inia bear marks and scars that have potential for being used in photo-identification studies (Martin and da Silva 2006). However, Trujillo (1994), McGuire and Henningsen (2007), and Gómez-Salazar et al. (2014) found that only a small proportion of the population could be identified correctly, not only due to the turbidity of the water, but also because of the behaviour, morphology, and ecological characteristics of the species (McGuire and Henningsen 2007, Gómez-Salazar et al. 2014). Great effort is required to obtain accurate data.

Inia feed on more than 43 species of fishes (Best and da Silva 1993, da Silva 2009).

Inia occur throughout the Amazon and Orinoco river basins in Brazil, Bolivia, Colombia, Ecuador, Peru, and Venezuela, from the deltas upstream to where impassable rapids, waterfalls, lack of water, and possibly low temperatures block their movement (Best and da Silva 1989a,b). In Brazil, they have been recorded in the central region, in the Araguaia-Tocantins River basin and in several tributaries such as the das Mortes and Verde, Paranã, Vermelho, Peixe, Crixas-Açú, and Água Limpa rivers and the dos Tigres and Rico lakes, all in the state of Goiás. They occur in Lake Montaria in the state of Mato Grosso, the Araguaia-Tocantins River basin, as well as mangrove habitats in Marajó Bay (Araújo and Wang 2012, Araújo and da Silva 2014, Hrbek et al. 2014, Siciliano et al. 2016a,b). Inia have also been observed in the following rivers and tributaries of the Amazon basin in Brazil – Juruá, Purus, Madeira, Tapajós, Xingu (only below Belo Monte falls), Içá, Caquetá-Japurá, Negro-Branco and Trombetas. In addition, in Brazil they have been reported along the Madeira mainstem above and below the Teotônio rapids (Gravena et al. 2014a). In Bolivia, they have been reported from the Beni (and Orton tributaries), Iténez or Guaporé (the Brazilian name) Basin (Verde, Machupo and Iporuporé tributaries), and Mamoré Basin and its tributaries -- Pirai, Grande, Ichilo, Chapare, Ibaré, Matucaré, Tijamuchi, Apere, Yacuma, and Yata (Pilleri and Gihr 1977, Aliaga-Rossel et al. 2006, Aliaga-Rossel 2010). In Colombia, they occur in the Orinoco and Amazon systems – in the Caquetá-Japurá River, from the Araracuara rapids to the mouth of the Apaporis River at the border with Brazil, the Putumayo-Içá River from Puerto Leguizamo to the east, and in the Amazon River. In the Orinoco, they are found in the rivers Meta, Arauca, Casanare, Bita, Vichada, Tomo, Tuparro, Orinoco, Guaviare (and the Guayabero affluent), Inírida, and Atabapo. Inia have been seen crossing the first set of rapids at Puerto Ayacucho (Atures-River Orinoco) during high water as well as the Cordoba rapids in the Caquetá River during low water (Trujillo et al. 2010c). In Ecuador, they are widely distributed in the main rivers and some lacustrine systems at elevations below 260 m in the rivers Payamino (near Napo River), Napo, Pastaza, Tigre, and Santiago (Best and da Silva 1993, Trujillo and Diazgranado 2002, Utreras et al. 2013). In the Ecuadorian Amazon, the only important river system in which Inia have not been recorded is the Morona River (Utreras 2001). In Peru, they can be found in the Ucayali and Marañon (and Samiria affluent) tributaries flowing generally north, and in the Napo, Tigre, and Pastaza tributaries flowing generally south (partial list from Best and da Silva 1989a,b; Leatherwood 1996, McGuire and Aliaga-Rossel 2010, Campbell et al. 2017). In Venezuela, they occur in the Orinoco system – in the delta region upstream at Ciudad Bolivar, Caicara del Orinoco, and near Puerto Ayacucho as well as in the Apure, Portuguesa, Guanare, Guaritico, Capanaparo, Cinaruco, and Caura rivers (Portocarrero-Aya et al. 2010). They occur in the Cassiquiare Canal, which connects the Orinoco with the Negro River (a tributary of the Amazon in Brazil), and also above and below the two sets of rapids at Puerto Ayacucho, which may (or may not) separate the Amazon and Orinoco populations (as summarized in Pilleri and Gihr 1977, Best and da Silva 1989a,b; Meade and Koehnken 1991).

The map shows where the species occurs or may occur. States for which confirmed records of the species exist are included in the list of native range states.

In July 2014, the Federal Government of Brazil published a rule (Normative Interministerial nº 6/2014) establishing a five-year moratorium on the fishing and marketing of the Piracatinga in Brazilian waters, effective from January 2015, intended to reduce the pressure on dolphins and other wild species (especially caimans, Caiman spp.) used for bait in this fishery (ICMBio-CEPAM 2017, IWC 2016). The report of the annual meeting of the International Whaling Commission’s Scientific Committee in 2016 stated the following (IWC 2017:355): “The Ministry of Environment (MMA) is responsible for evaluating the success of the moratorium. A working group was established by the MMA … to define procedures and monitor the fishing and marketing of piracatinga during the moratorium period. … three inspections to assess compliance with the ban were completed in 2016 and included: ‘Routine Operation’ in the municipalities of Iranduba, Itacoatiara, Manacapurú and Manaus in February, ‘Operation Golden Dragon’ in the municipalities of Maraã, Tefé and Fonte Boa in March-April and ‘Operation Federal Rios’ in the municipalities of Jutaí, Tabatinga, Coari, Fonte Boa and Tefé also in March-April.” The report went on to note (IWC 2017:355): “Brazil has established a National Action Plan for the Conservation of Small Cetaceans which lists Inia geoffrensis as an endangered species. This plan is intended to reduce human impacts and increase knowledge on small cetaceans in Brazil. Furthermore, the Brazil Government is cooperating with Colombia and Peru to support sustainable development of fishing activities. Several meetings and workshops involving these countries have included discussions on the catch and sale of piracatinga." Based on documentation of high levels of mercury in Piracatinga, the government of Colombia announced in August 2017 a permanent ban on the trade of this fish within the country.

The status of Inia has been evaluated in different range states during the last 10 years following the IUCN criteria and those national assessments have classified the species as Endangered (Trujillo et al. 2006, Aguirre et al. 2009, Tirira 2011, Rodríguez and Rojas-Suarez 2015). Additionally, a South American River Dolphins Action Plan (Trujillo et al. 2010a) and national action plans has been produced for Bolivia (2012), Ecuador (Utreras et al. 2013), and Colombia (Trujillo et al. 2014). Action plans for Peru and Venezuela are in preparation. In Colombia, there are also regional action plans for the Orinoco and Amazon basins (Trujillo et al. 2008, Mosquera et al. 2016). In Brazil, the "National Action Plan for the Conservation of Aquatic Mammals – Small cetaceans" was published in 2011.