Ecologia alimentar da ariranha (pteronura Brasiliensis) e da lontra neotropical (lontra Longicaudis) no parque nacional do Jaú, Amazonas, Brasil

Abstract

The giant otter (Pteronura brasiliensis) and the neotropical river otter (Lontra longicaudis) are two species of carnivorous mustelids belonging to the Lutrinae subfamily, which feed mainly on fish. These two species coexist in the Jaú National Park, in Central Brazilian Amazon, and the supposed similarity in the diet could generate interactions between them. This study describes and compares the diets of the giant otter and the neotropical river otter in the lower Jaú and Carabinani rivers, through the analyses of fecal samples collected between 2006 and 2008 (82 giant otter and 75 neotropical river otter). About 85% of the samples were collected during the dry season, which limited the analyses to the low water period. The giant otter feeds mainly on fish of the Cichlidae (frequency of occurrence = 91.5%), Erythrinidae (74.4%) and Characidae (29.3%) families, while the neotropical river otter consumed mainly fish of the Doradidae (75.3%), Loricariidae (26.7%) and Cichlidae (25.3%) families. The two otter species showed low similarity in their diets (Pianka’s Index = 0.16), which possibly reflects the use of different microhabitats and foraging tactics and the abundance and richness of fish in the Amazon. The giant otter catch larger and more active fish (eg. anostomids and large characins) than the neotropical river otter, which probably scans the substrate in shallow river parts in search of slower, sedentary and nocturnal (mainly small catfish) fish. Other than fish prey (reptiles, rodents and aquatic invertebrates), although uncommon in the diet of both otter species, were more frequent in the diet of the neotropical river otter that in the giant otter. Moreover, the giant otter ate a greater diversity of fish families than the neotropical river otter. In this sense, the neotropical river otter seems to be more specialized in capturing certain types of fish, showing a clear preference for the consumption of small catfish of the Doradidae family. The results indicate litter overlap in the diet, but no indication of trophic interaction between giant otters and neotropical river otters in Jaú National Park.