Habitat use and population estimates of otters before and after damming of Salto Caxias Reservoir, Iguaçu River, Paraná, Brasil

Abstract

The neotropical otter Lontra longicaudis (Olfers, 1818) is a semi-aquatic mammal that inhabits rivers, lakes and coastline. Although it has been recorded in artificial lentic environments, little is known about the impacts of reservoir creation on their populations. This paper aims to compare the habitat use and population estimates of the neotropical otter in the area of the reservoir Salto Caxias Hydroelectric Power Plant, before and after damming. The study area includes the portion of the Iguacu River and its tributaries from Salto Caxias dam until Chopim River, upstream, totaling about 80 km. We performed four field surveys before the impoundment (pre-damming) and four field surveys 17 months after it (post-damming). During the surveys the Iguacu River and its tributaries were covered in a motor-boat, near to the bank, to record and characterize defecation sites and dens. Data collected in the field were tabulated according to the occurrence in 112 squares (2 km x 2 km). The number of resident females (y) was estimated from the number of dens (x), pre and post-damming, through the regression equation: y = 0.331x + 0.238. Most of the quantitative parameters for evaluating the presence and activity of otters declined in the post-damming. The distribution of defecation sites was aggregated and the main aggregation factors are dens and mouths of major tributaries. Dens were found in cavities under the roots of riparian vegetation during pre-damming, turning to cavities between rocks in the post-damming. Four resident females were estimated in the pre-damming (y = 4.21) and two in the post-damming (y = 2.22). Key words: neotropical otter, hydroelectric power plant, environmental impacts, Iguacu River, dens, defecation sites.