The polymorphic major histocompatibility complex (MHC) has gained a specific relevance in pathogen resistance and mate choice. Particularly the antigen-binding site (ABS), encoded by exon 2 of the DRB class II gene, exhibits numerous alleles and extensive sequence variations between alleles. A lack of MHC variability has attributed to instances such as bottleneck effects or relaxed selection pressure and has a certain impact on the long-term viability of the species concerned. As a result of seriously decreased population density during the last century, the current population of the endangered European mink (Mustela lutreola, L. 1761) has suffered from geographic isolation. In this study, we amplified a partial sequence of the MHC class II DRB exon 2 (229 bp), assessed the degree of genetic variation and compared the variability with those of other Mustelidae. As a result, nine alleles were detected in 20 investigated individuals, which differ from each other by four to 25 nucleotide substitutions (two to 11 amino acid substitutions). Whilst an equal ratio for synonymous and non-synonymous substitutions was found inside the ABS, synonymous substitutions were significantly higher than non-synonymous substitutions in the non-ABS region. Results might indicate that no positive selection exists within the ex situ population of M. lutreola, at least in the analysed fragment. In addition, phylogenetic analyses support the trans-species model of evolution.

As an attempt to help conserve the endangered European mink Mustela lutreola (Linnaeus, 1761), a reintroduction program was started in a nature reserve in Saarland, Germany; the present study is part of this ongoing reintroduction project. Within the first 2 yr period, 48 (16 m, 32 f) founder animals were reintroduced, out of a total of about 75 animals intended for release in the course of the 3 yr project. Prior to reintroduction, the animals were acclimatized using soft-release pens where they were preconditioned with natural prey . A number of individuals (n = 18) were set free in groups of mating partners (ffm, fm) and in mother-offspring groups. Thirty-three European mink (14 m, 19 f) were fitted with intraperitonial transmitters and radio-tracked and surveyed via live-trapping. Animals were monitored from April 2006 to May 2008 to determine the distribution, size and temporal changes in home range. Released animals showed linear home ranges spreading along rivers and brooks. Home range sizes were 7.2 km (88 ha) for 1 adult male, 0.2-5.9 km (1-505 ha) for adult females, around 1.7-5.6 km (17-132 ha) for juvenile males and 9.2 km (778 ha) for 1 juvenile female, respectively. The released adults showed inter-, but only few intra-, sexual home range overlaps. In contrast, juveniles did not show any home range overlaps. In winter, home range size decreased to a minimum of about 1 km. Further, home range size for females decreased around parturition but increased successively at time of weaning. The activity pattern of released animals was highest at night (especially around dusk and dawn).