Influence of the water quality on the occurrence of the Neotropical otter (Lontra longicaudis) (Olfers, 1818) in a human-altered river basin

Abstract

The seeming tolerance of the Neotropical otter (Lontra longicaudis) to human-altered environments does not prevent it from being under threat in several areas across its distribution range. To improve our knowledge of the tolerance of the species to increasing levels of habitat degradation, and adding ecological information, we evaluated the influence of water quality, vegetation structure, seasonality and stream flow on the occurrence of L. longicaudis. We conducted monthly samplings of non-invasive biological material in 16 points across different classes of water quality in the Sinos River Basin in Rio Grande do Sul, Brazil, between January and August 2015. Water quality and stream flow positively influenced the occurrence of L. longicaudis; still, the species seems to reduce its occurrence only in waters of very low quality, showing tolerance to moderate levels of eutrophication. We conclude that the Neotropical otter is tolerant to human-altered environments, but beyond a certain threshold of water-quality degradation, otter persistence is at risk. Monitoring water quality is key for the preservation of riverine ecosystems, and measures to control water pollution and eutrophication are deemed necessary to guarantee the preservation of viable Neotropical otter populations across its distribution range.