Multiple paternity and reproductive tactics of free-ranging American minks, Mustela vison

Demography and spatial patterns of free-ranging American mink were documented by continuous year-round trapping and radiotracking along 24 km of the River Thames in England, United Kingdom. An estimated average of 1.19 ± 0.58 SE minks per month were present between May 1995 and August 1997. Kit and juvenile paternity was assessed using 7 microsatellite markers and we observed evidence that multiple paternity occurred in this population. Although males maintained territories during most of the year, they sired litters in areas beyond their territory boundaries. We suggest that a male's inability to monopolize paternity, along with a female's ability to continue ovulation after successful matings (i.e., superfetation) explains why males abandon territoriality during the breeding season. We suggest that the main function of a brief delayed implantation of this species may be to enable female mink to retain superfetation, which facilitates the fertilization of ova from different ovulations by different males. This mink model, consisting of disarticulating residency from fatherhood and the possibility of superfetation, may occur more widely among related species and requires a re-evaluation of mustelid sociobiology.