Mortality and reproductive patterns of wild European polecatsMustela putorius in Denmark

Abstract

Accurate information about age structure, survival and reproductive biology is a prerequisite for understanding various aspects of a species' population ecology and life history biology (Stearns 1992), for constructing models of population dynamics (Vandermeer and Goldberg 2003) and for developing management strategies (Caughley 1977). Examinations of carcasses of harvested or accidentally killed individuals are a widely used method to establish life tables as well as to ascertain reproductive information such as maturity age, seasonal distribution of conceptions and litter size. In particular, this kind of information is crucial to species that are difficult to mark and recapture, such as almost all small or medium sized carnivorous mammals eg otter Lutra lutra (Linnaeus, 1758) (Hauer et al. 2002), fishers Martes pennanti (Erxleben, [371] Acta Theriologica 52 (4): 371-378, 2007. . 2007. Mortality and reproductive patterns of wild European polecats Mustela putorius in Denmark. Acta Theriologica 52: 371-378.Despite its relative abundance and wide geographical range, the population dynamics and reproductive biology of the European polecat Mustela 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.

Feral ferrets (Mustela furo) as hosts and sentinels of tuberculosis in New Zealand

“…In the Mackenzie Basin, survival of juveniles varied from 19% to 100% in the 4 months after emergence from the natal den, decreasing to 0–60% by the end of the first winter, depending inversely on ferret density (Byrom 2002 ). Annual survival rates of 15–65% have been reported for feral ferrets in New Zealand (Norbury and Heyward 1997 ; Morley 2002 ; Byrom et al 2008 ), similar to reported rates of 32–67% for the polecat in Europe (Kristiansen et al 2007 ). Due to the high annual mortality rate among ferrets, they are regarded as less likely to contribute to risk of TB persistence than longer-lived wildlife hosts of TB in New Zealand, such as wild deer (Barron et al 2013 ; Nugent et al 2015b ).…”

The presence of rabbits adjacent to roads increases polecat road mortality

“…In other geographic regions, where the ecology of the polecat is better known, road fatalities are also a major cause of polecat deaths (Blandford 1987;Birks 1997;Mitchell-Jones et al 1999;Lodé 2003;Kristiansen et al 2007). Despite these Wndings and that road-kills seem to be concentrated along certain stretches of road (Blandford 1987), no studies have analysed habitat and road-related variables at speciWc locations where road-kills occur.…”

Reproduction of the red fox Vulpes vulpes in western France: does staining improve estimation of litter size from placental scar counts?

“…Since uteri from all categories of females are readily obtained from hunters and trappers; placental scars are often the best source of information on fox reproduction. Counting of placental scars and embryos in the uterus has been widely used in a number of mammalian species, including several rodents (Martin et al 1976), lagomorphs (Bray et al 2003) and carnivores (Lindström 1994;Helle and Kauhala 1995;Mowat et al 1996;Asano et al 2003;Elmeros et al 2003;Elmeros and Hammershøj 2006;Kristiansen et al 2007) to estimate female fecundity in free-ranging populations. Indeed, in mammals with a zonary endoepitheliochorial or discoid hemochorial type of placenta, a distinct implantation site is formed for each foetus in the uterus.…”