The distribution of macro-crustaceans in Argentinean Patagonia: multiple scale analysis of the role of resource availability in wildlife distribution.

CASSINI, M.H., FASOLA, L., AUED, B., CHEHÉBAR C., MACDONALD. D.W

Hwacheon, Corea del Sur

Simposio; IUCN Xth International Otter Colloquium.; 2007

In this paper we use a multi-scale approach to evaluate resource distribution for the identification of environmental determinants of the distribution of a species with conservation requirements. The objectives are: (1) describe the distribution, in the Andean Patagonian region of Argentina, of macro-crustaceans of the genera Aegla and Sammastacus (main prey of the Southern river otter Lontra provocax), (2) analyse environmental factors associated with crustacean distribution, and otter distribution, at different spatial scales, and (3) discuss the importance for wildlife ecology of the resource distribution patterns at different scales. We used five different sources of information to establish the distribution of crustaceans: (1) crustaceans surveys in northern and southern Patagonia (2) other indicators (mink diet analysis, location of rests of crustaceans external skeletons and interviews to local people). Macro-crustaceans showed strong heterogeneities in their distribution at four ecological scales: They occur in lakes in northern, but not southern, Patagonia. In northern Patagonia, they were found in four of six basins. Within a basin, there was a longitudinal and altitudinal gradient, with low crustacean density in lakes at high altitudes. Within lakes, they were significantly more abundant on rocky bottoms than on coasts with stones, gravel or rush vegetation. The latitudinal and altitudinal gradients, the basin differences, and the local heterogeneities can be explained by thermal gradients, water body productivity, geological history and crustacean’s behaviour, respectively. Southern river otter distribution matches macro-crustaceans distribution at the proper ecological scales, strongly suggesting that one of the main factors that regulates the distribution and abundance of L. provocax is the availability of this type of prey.