This study analyses quantitatively the association between habitat characteristics and annual variation
in water availability on otter (Lutra lutra L.) distribution in a large Mediterranean area (13717 km(2)) in southern
Spain.
There was a strong positive correlation between habitat quality, estimated after the two first components of a
principal component analysis of a matrix of habitat variables x sites, and an index of otter presence/absence, otter
presence being most commonly associated with unpolluted and undisturbed sites surrounded by woodland.
After univariate analysis, the main freshwater habitat features were statistically different between sites with otters
and sites lacking them. In general, otters occurred in medium-sized fluvial habitats, with high bankside vegetation
cover, unpolluted, with low or very low human disturbance and surrounded by forests or dehesas (Mediterraneanlike
savannah).
Water availability, inferred from the water balance, strongly influenced otter distribution and the type of water
body used the most. As water availability increased so did the otter distribution range and during these: periods they
tended to colonize low-order streams. During periods of water shortage, otters were usually found in high-order
streams and reservoirs, the only sites that kept water.
This work shows that otter distribution in Mediterranean areas is strongly influenced by two factors - maninduced
habitat degradation and natural variability in water availability. The addition of the second factor to the first
one introduces additional risks to the survival of otter populations in Mediterranean areas compared with more
northerly and humid areas. Copyright (C) 2001 John Wiley & Sons, Ltd.