Investigating the Impact of Intensified Seasonal Fluctuations in Water Levels on Habitat Use and Population Trends of Pink (Inia geoffrensis) and Grey River Dolphins (Sotalia fluviatilis) in the Peruvian Amazon

Abstract

According to the International Panel on Climate Change, climate will undergo continual, relatively rapid change during this century. Recent climate models for the western Amazon Basin have further hypothesized the subsequent exacerbation of intensified water-level cycles in the form of increased droughts in the dry season and increased flooding in the wet season. In light of these anticipated climatic variations, conservation scientists must understand how hydrological intensification leads to ecological, behavioral, and population changes in Inia geoffrensis and Sotalia fluviatilis, as an understanding of these changes is crucial in maintaining sustainable levels of wildlife and human resource in the Pacaya-Samiria National Reserve, Peru (PSNR). Thus, the goal of my research is to assess how intensified hydrological changes that occurred during the years 2013-2018 impacted the abundance, habitat use, and population dynamics of the two Amazon freshwater cetaceans in this area. My hope is that this research will aid in identifying and implementing the necessary advances or shifts that must take place in conservation and management in the Peruvian Amazon to enhance the survival of these endangered species. My findings indicated that habitat use was similar between the two species in the dry season and differed in the wet season, most probably due to migratory movements of fish, the species’ morphological characters, and the reduction and expansion of habitats that occurred due to intensified hydrological changes. Furthermore, my 6-year time series of standardized surveys showed that both species were in similar, steep declines across the study period. Finally, population trend analyses among the different habitats depicted that the main river and narrow channels suffered significant declines in abundance in the intensified, drier seasons. Taken together, these results indicate that the intensification of seasonal water levels leads to major, often negative, shifts in Amazon populations of Inia and Sotalia, urging the development of specific region-specific conservation and management plans in the PSNR. Future research must continue to monitor dolphins and investigate the dolphins’ seasonal induced movements, as natural and human pressures in the Amazon basin are only anticipated to worsen with time.