Serious declines in populations of native European mink (Mustela lutreola) have occurred in Europe. One responsible factor may be infectious diseases introduced by exotic American mink (Mustela vison). In order to investigate a possible role for Aleutian mink disease parvovirus (ADV), we surveyed native riparian carnivores and feral American mink. When serum samples from 12 free-ranging European and 16 feral American mink were tested, antibodies to ADV were detected from three of nine European mink. ADV DNA was detected by polymerase chain reaction in whole cell DNA from four of seven carcasses; two American mink, one European mink and a Eurasian otter (Lutra lutra). Lesions typical of Aleutian disease were present in one of the American mink. A portion of the ADV VP2 capsid gene was sequenced and the results suggested that two sequence types of ADV were circulating in Spain, and that the Spanish ADVs differed from other described isolates from North America and Europe. Future conservation and restoration efforts should include measures to avoid introduction or spread of ADV infection to native animals.

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Litters of small Eurasian otter (Lutra lutra) cubs ranged from one to four, with those of one and two accounting for 95%. Significant variations were found between locations and according to the main diet (average ranging between 1.1 and 2.4 cubs/female). We found a seasonal pattern in otter breeding in some areas, being different in each. In the Prepyrenees, most births took place between March and June (85%). In Mediterranean rivers of the Ebro basin, most births occurred between December and February (57%). In both, the small cubs were found outside the dens just 2–3 months after the time of birth. Fish and crayfish exhibited a seasonal fluctuation, with a maximum density of biomass between the end of spring and the end of summer and minimum densities in winter. Water was always flowing in the Pyrenees and Prepyrenees rivers; however, in Mediterranean rivers, important periods of drought were observed, concentrated especially in summer and some winters. Timing of birds corresponded to variation in abundance of food (energy needs) and water resources in space and time. The presence of adequate prey species for the cubs (Ebro's barbel (Barbus graellsii and Barbus haasi) and American crayfish (Procambarus clarkii) in our study area) plays an important role. Interannual variations in food can affect the otter's reproductive cycle and breeding success.

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The population genetic structure of an invasive species in Spain, the American mink (Mustela vison), was investigated using microsatellite DNA markers. This semiaquatic carnivore, originating from North America, was imported into Europe for fur farming since the beginning of the 20th century. Due to massive escapes, farm damages, deliberate releases and/or accidents, feral mink populations were established in the aquatic ecosystems of many European countries, including Spain. We genotyped 155 American mink originating from the Spanish regions Basque Country, Catalonia, Castilla-Leon, Aragon, Valencia and Galicia using 10 polymorphic microsatellite loci to highlight population genetic structure, distribution and dispersal. M. vison populations in Spain appear differentiated and not yet connected by gene flow. Bayesian clustering analyses and spatial analyses of molecular variance detected four inferred clusters, overall coinciding with the sampled geographical localities. Preliminary testing shows moderate to large estimated effective population sizes. Molecular analyses result useful to provide baseline data for further research on the evolution of invasive mink populations, as well as support local management strategies and indirectly benefit the conservation of threatened species in Spain, such as the endangered European mink (Mustela lutreola), and the polecat (Mustela putorius), which share the habitat with the American mink.