Demographic structure of three riparian mustelid species in Spain

Age estimation of three mustelid species with similar body size was performed in Northern Spain. Canine samples of 1766 carcasses from 1661 American mink (Neovison vison), 54 European mink (Mustela lutreola), and 51 European polecats (Mustela putorius) were sectioned, and cementum annuli counts in tooth sections were used for age estimation. American mink samples consisted primarily of trap-captured animals from governmental control campaigns, whereas road casualties were the principal origin of European mink and European polecat carcasses. Individuals prior to their first breeding season (class 0+) represented approximately half of all animals, with no significant differences between species or causes of death. Differences in sub-adult percentages were observed between the pre- and post-reproductive period, with a high mortality during the dispersal-winter period in all three species. Frequencies of mortality of the sub-adult age class were 0.46, 0.50, and 0.55 for American mink, European mink, and European polecat, respectively. Survival rates of the American mink were higher than those of the native species. The oldest animals detected were 7+, 5+, and 3+ years old for the American mink, European mink, and European polecat, respectively. No differences were observed in mean age of animals found dead as road casualties in all three species or between captured American mink and road casualties. The information obtained is of high value for understanding the demographic processes of the populations and particularly for conservation and management decisions for these species.