Environmental correlates of the distribution of southern river otters Lontra provocax at different ecological scales

M. B. Aued a1, C. Chéhebar a2, G. Porro a3, D. W. Macdonald c1 and M. H. Cassini a4
a1 Departamento de Ciencias Básicas, Universidad Nacional de Luján, Rutas 5 y 7, 6700 Luján, Argentina
a2 Delegación Regional Patagonia, Administración de Parques Nacionales, Vicealmirante O'Connor 1188 – 8400 San Carlos de Bariloche – Río Negro, Argentina
a3 Intendencia del Parque Nacional Nahuel Huapi – San Martín 24 – 8400 San Carlos de Bariloche, Río Negro, Argentina
a4 Departamento de Ciencias Básicas, Universidad Nacional de Luján, Rutas 5 y 7, 6700 Luján, Argentina and Organización PROFAUNA, Corrientes 1145 4° 47, 1043 Buenos Aires, Argentina


Endangered southern river otters Lontra provocax (huillin) are confined to southern Chile and three isolated areas of Argentina, the most important being the Nahuel Huapi National Park, where distribution surveys were conducted in 1983, 1995 and 2000. We used these survey data together with a Geographical Information System analysis to elucidate the factors that are important in determining huillin distribution at different ecological scales. There were significant heterogeneities in the distribution of huillin between river basins, between habitats, between lakes relative to dispersal routes and topography, and between sample points within a lake. From these analyses three factors emerge as potentially related to huillin distribution, and further elucidation of these are suggested as priorities for research to underpin the species' conservation. These factors are: a) the distribution of crustacean prey, with absence of huillin from one river basin and from mountainous streams correlated with low densities of crustaceans in these places; b) human habitation, which may explain why huillin dispersed southwards, but not northwards, from the main lake, although underwater visibility may also be relevant; c) the presence of the introduced American mink Mustela vison, because although there was a positive relationship between the occurrence of mink and huillin in Lake Nahuel Huapi, there was a negative relationship in their occurrence between other lakes. We discuss possible explanations for all three factors.

(Received September 17 2002)
(Revised March 11 2003)
(Accepted May 6 2003)

Key Words: American mink; Argentina; ecological scale; huillin; Lontra provocax; macro-crustacean; Mustela vison; Nahuel Huapi National Park; southern river otter.

c1 Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK. E-mail: david.macdonald@zoo.ox.ac.uk