Mortality and reproductive patterns of wild European polecats<Emphasis Type="Italic">Mustela putorius</Emphasis> in Denmark

Despite its relative abundance and wide geographical range, the population dynamics and reproductive biology of the European polecatMustela putorius Linnaeus, 1758 are largely unknown as to the wild living. We therefore investigated age and reproductive status of 239 Danish polecats primarily killed in traffic or trapped during 1998–2004. Males comprised two third of all individuals in all age groups. Based on a static life table, apparent annual mortality was 68% during the first year of life, 33% during the second year and 65% from the third year in both sexes. The mean (± SE) litter size of 5.95 ± 0.62 (n = 18), estimated from placental scar counts, was significantly lower than litter sizes at birth reported for captive individuals but consistent with litter sizes reported for wild polecats in Russia. Female yearlings conceived at the same rate and produced litters of the same size as older individuals.Males had spermatozoa in their testes from February through August. Testes mass peaked in April and May, ie the same period when most females conceive. A lower prevalence of individuals with spermatozoa in yearlings suggests that most males postponed sexual maturity to two years of age.