Abstract :
[en] More than 1500 otter spraint samples have been collected in different aquatic habitats throughout the present geographic range of the otter in France. Prey remains were identified, the relative occurrence and abundance of each species was assessed and the biomass of each individual prey estimated. When available, data about the fish communities (size frequency- distributions, relative abundance) were compared with the diet of the mustelid. The main conclusions of the study are as follows: 1. The otter is mainly piscivorous but some other aquatic (crayfish) or semiaquatic preys (frogs, Natrix-snakes, some birds and mammals) are of major dietary importance in oligotrophic habitats. 2. The composition of the diet is determined by the local fish resources. The otter is an opportunistic predator, its diet varying greatly from one place to another. The diet can also change depending upon the season or upon some special circumstances such as frog or fish reproduction or strong prey-community changes. 3. Small fish are dominant in the diet. No size selection has been evidenced at least in the eel and in the cyprinid fishes. As far as the trout is concerned, it seems that the otter consumes preferably medium sized individuals. 4. The proportion of some prey species is lower in the diet than in the habitat. These are the more pelagic (bleak, sander, breams), rheophilic (dace, chub) or group-living species (minnow, roach). Bottom- (bullhead, eel, tench, gudgeon, barbel) or plant-living (rudd, pike) species are more frequent.
