Ecology of the neotropical otter (Lontra longicaudis) in southern Tehuacán-Cuicatlán Biosphere Reserve, Mexico

Land otters are predators at the top of the food chain in the rivers where they live and mold the biotic communities at lower trophic levels. The neotropical otter, Lontra longicaudis, is widely distributed in the Americas, but populations are being decimated by hunting, habitat loss, water pollution, and roadkills. An otter population was located in southern Tehuacán-Cuicatlán Biosphere Reserve (TCBR), Mexico. Surveys were conducted in the dry season to determine otter presence, to record physical-chemical data and to collect scats to determine their populational densities and feeding habits. River width and depth, dissolved oxygen and elevation were the significant variables that explained their presence. In the rivers where otters were present, we estimated densities between 0.19 and 0.22 otters/km. We found 12 prey taxa, mainly freshwater fish. In this protected area, the neotropical otter is restricted to large rivers at low elevations, and populations are low. Although otters have diverse feeding habits, they mainly prey upon Poeciliopsis spp., which constituted 60% of the scats. Density estimates comprise the dry season and were lower than previous surveys, therefore it is necessary to conduct yearly monitoring to identify trends and to implement actions focused on their conservation and management.