Trophic niche comparison of three mustelids in southwestern France

Abstract

The European mink, Mustela lutreola, is the most threatened carnivore in the world particulary in France. He lives only in the southwestern departements: Pyrénées-Atlantiques, Landes, Gironde, Lot-et-Garonne, Dordogne, Charente and Charente-Maritime. The causes of the decline in mink populations were addressed in a multidisciplinary manner with food being a key factor. Data on mink prey were scarce, particularly due to confusion between the faeces of the polecat (Mustela putorius) and those of the mink. A few individuals of both species have been equipped with a transmitter collar in three sites: two rivers, one in the Garonne basin (the Ciron, near Langon), anothe leading into the Arcachon basin (the Eyre) and a large pond, north of Bayonne (Orx). The faeces were therefore collected per individual. The objective was to have results on the feeding of Mink and, above all, the possible competition of three mustelids. Overall, mink consumes anurans (31 %), birds (25%), mammals (24 %) and fish (19 %), while polecal it more specialized for anurans (61 %) and mammals (30 %). However, between anurans, the polecat catches mainly toads (90.8 %) while the mink catches frogs (73.4 %). For mammals, we see a separation of prey between polecat and mink respectively: lagomorphs (44 % vs 0.4 %), small rodents (27 % vs 15 %), rats (12 % vs 39 %), water voles (7% vs 32 %). The overlap index of the trophic niche is one third (0.34) considerinq that prey are quite abundant in the three sites, the competition is relatively low. For the otter (Lutra lutra), spraints were collected only along the Eyre River. Therefore, trophic niche comparisons were calculated on two mink (M1E, one female, and M3E, one male) and five polecats, including only one female with only four faeces. The recovery index is minimal of otters, which mainly consume fish, lamprey and aquatic insects, few amphibians. However, the data must be criticized: minks and polecats have a different diet per individual. It cannot be excluded that these are individual preferences. In addition, the samples are not random or independent