Home range and movements of Amazon river dolphins Inia geoffrensis in the Amazon and Orinoco river basins

Abstract

Studying the variables that describe the spatial ecology of threatened species allows us to identify and prioritize areas that are critical for species conservation. To estimate the home range and core area of the Endangered (EN) Amazon river dolphin Inia geoffrensis, 23 individuals (6 female, 17 male) were tagged during the rising water period in the Amazon and Orinoco river basins between 2017 and 2018. The satellite tracking period ranged from 24 to 336 d (mean +/- SE = 107 +/- 15.7 d), and river dolphin movements ranged from 7.5 to 298 km (58 +/- 13.4 km). Kernel density estimates were used to determine minimum home ranges at 95% (K-95 = 6.2 to 233.9 km(2); mean = 59 +/- 13.5 km(2)) and core areas at 50% (K-50 = 0.6 to 54.9 km(2); mean = 9 +/- 2.6 km(2)). Protected areas accounted for 45% of the K-50 estimated core area. We observed dolphin individuals crossing country borders between Colombia and Peru in the Amazon basin, and between Colombia and Venezuela in the Orinoco basin. Satellite tracking allowed us to determine the different uses of riverine habitat types: main rivers (channels and bays, 52% of recorded locations), confluences (32%), lagoons (9.6%), and tributaries (6.2%). Satellite monitoring allowed us to better understand the ecological preferences of the species and demonstrated the importance of maintaining aquatic landscape heterogeneity and spatial connectivity for effective river dolphin conservation.