Introduction

The otter (Lutra lutra), a semi–aquatic mustelid, has suffered a significant population decline in Europe (Mason & Macdonold, 1986; Foster–Turley et al, 1990). There are several possible causes, although without doubt pollution, the destruction of habitat and the variation of available food have played an important part (Macdonald & Mason, 1992; Kruuk, 1995). The species is one of the most intensively studied of all European mammals, primarily because of its status as a bioindicator species at the top of many freshwater food chains. It has also become an emblem of many conservation projects throughout the world. All these studies have been carried out in coastal environments or in areas of relatively low altitude. This is because few European countries with populations of otters have any significant land that is higher than 1000 m above sea level (a.s.l.) (e.g. Norway, France, Slovakia, Slovenia, Croatia, Bosnia, Yugoslavia, Greece, Bulgaria, Rumania and Spain). In several, the otter has become extinct or scarce, and only two (Greece and Spain) have otter populations in large mountain ranges that exceed 2000 m a.s.l. This means that the effect of altitude, a significantly limiting factor for many species, has not been studied for otters.

Mason & Macdonald (1986) point out that L. lutra kutab has been observed at 4120 m in Tibet; others report that it is more abundant in low areas, with fewer tracks and signs with increasing altitude (Green & Green, 1980; Chapman & Chapman, 1982; Delibes, 1990).