Spatial Ecology Applied to Identify Differential Uses of Habitat Types and Hotspots of Amazon River Dolphin Activity

Abstract Context: Identifying the heterogeneity in the habitat use and hotspots of Amazon River dolphin activity is essential to design effective strategies for the management and conservation of these cetaceans and their habitats in the Colombian Amazonas River and Orinoco basin.Objectives: Quantify the differential use of habitat that Amazon River dolphins exhibit and to identify hotspot activity during seasons of rising waters in the Colombian Amazonas River and other major rivers in the Orinoco basin.Methods: Based on processed satellite images Landsat 8 (2018-2022), we classified habitat types used by I. geoffrensis and reported in the literature: (1) main river, (2) confluences, (3) tributaries, (4) channels, (5) islands, (6) bays, and (7) lagoons. We combined this dataset with GPS location data obtained from 17 tagged Amazon River dolphins to quantify the proportion of habitat types used, and we used GAMLSS to explore the relationship between the number of locations per habitat as the predictor variable and nine response variables. Kernel density estimate (KDE) analysis was used to identify both areas used (K95) and hotspot activity associated with core areas (K50) in the habitat types for the individuals monitored in the Amazonas River and Orinoco basin. Results: Satellite tracking of I. geoffrensis individuals reported 16.098 locations (Amazonas River, n = 2.934 locations and Orinoco basin, n = 13.164 locations) classified into seven habitat types. For the analyzed period (rising waters) main habitat types used were as follow: in the Amazonas River (1) main river (n = 1.346, 46%), and (2) lagoons (n = 1.158, 39%); and in the Orinoco basin (1) main river (n = 7.798, 59.2%), and (2) channels (n = 1.535, 11.7%). The best fitting GAMLSS for the I. geoffrensis monitored individuals in the Amazonas River showed that body length, sex, and habitat types (lagoons and main river) were significant predictors of Amazon River dolphins; and in the Orinoco basin they showed that body length, longest distance, K50, and habitat types (confluences, lagoons, main river, and tributaries) were significant. Individuals monitored in the areas evaluated in the Amazonas River reported K95 ranged: 30.7–105.5 km2 (mean = 62 ± 32), and the K50 or hotspots of activity were recorded in the main river, confluences, lagoons, and tributaries. In the five rivers of the Orinoco basin, monitored individuals registered K95 ranged: 6–116 km2 (mean = 32.8 ± 31.53), and hotspots of activity were recorded in the main river, islands, channels, confluences, bays, tributaries, and lagoons.Conclusions: Evaluation of differences in habitat type use and identification of hotspot activity will contribute to improving management and conservation efforts for the populations of these cetaceans in the Colombian Amazonas and Orinoco basins.