Estimating occupancy and detection probability of the Amazonian manatee (Trichechus inunguis), in Central Amazon, Brazil

Density and abundance estimation of West Indian manatee, Trichechus manatus, between the states of Ceará and Piauí, Northeast Brazil, using active acoustics

“…However, aerial survey studies in relatively clear waters reported detection probability higher than 50% [e.g., Potiguar Basin, Brazil (Petrobras, 2014); Tampa Bay, USA (Edwards et al, 2007)]. In dark waters, Souza et al (2021) reported an Amazonian manatee (T. inunguis) detection probability of 50% combining boat surveys and indirect evidence of presence (feeding trails, feces presence, and manatee sound emissions); and Narváez Ruano et al ( 2021) reported similar values using side-scan sonar to detect Amazonian manatee.…”

Advances in the knowledge of the biology and conservation of the Amazonian manatee (Trichechus inunguis)

“…Recently, some studies applied or suggested different and innovative methodologies to estimate the occurrence of Amazonian manatees. Souza et al (2021b) utilized a combination of visual effort for individual observation and indirect evidence (feces and feeding records) based mainly on the skills of experienced former manatee hunters in identifying the presence of the animals, while Brice (2014) and Ruano et al (2021) used a fish finder side-scan sonar to detect Amazonian manatees' presence in the evaluated area. Additionally, Hunter et al (2018) suggested the use of eDNA as a tool for estimating the occurrence of Amazonian manatee, as promising results have been obtained with T. manatus in the wild (Lozano-Mojica & Caballero, 2021).…”

“…Therefore, it is difficult to extrapolate the routes and distances of migration to all species' range due to the heterogeneity of habitats, degree of anthropogenic impact (historical and current hunting) and habitat alteration (Arraut et al, 2017). In Piagaçu-Purus Reserve, lower Purus River, Brazil, manatees additionally occupy floodplain lakes during the low-water season (Souza et al, 2021b). In this case, other effects such as the largest distance to the ria lake and appropriate conditions (e.g.…”

“…In this case, other effects such as the largest distance to the ria lake and appropriate conditions (e.g. larger lakes and reduced risk posed by humans) can maintain the animals in the várzea lakes during the dry season (Souza et al, 2021b). In the Negro River basin, Crema et al (2019b), through interviews with local people, also reported the migratory behavior of the species, determined by the hydrological cycle.…”

“…Post-release monitoring offers an opportunity for the development of ecological and behavioral studies of the species in the wild, and also in the construction of awareness strategies of riverine communities of the manatee release sites. At this moment, about 150 Amazonian manatees are undergoing rehabilitation in authorized captive facilities in Brazil, Colombia and Peru, most of them with a large potential group ready to release (Souza et al, 2022). Faced with this situation, the strengthening of Amazonian manatee release programs by the governments of these countries is strategic and extremely necessary to ensure this important conservation approach of the natural populations of the species.…”