Implantation and Parturition Dates of North American River Otters, Lontra canadensis, in Southern Missouri

Abstract

Despite numerous studies of reproductive dynamics of the North American River Otter (Lontra canadensis), relatively little information exists on the implantation or parturition dates of North American River Otters in the wild. We collected carcasses of North American River Otters that had been legally harvested in southern Missouri, USA, between 1997 and 1999 as part of a larger population dynamics study. Embryos (n = 28) were removed from a subset of North American River Otters (n = 9) during necropsy. Using harvest dates and crown–rump length measurements of embryos, we estimated implantation dates, which ranged from 7 December to 12 January, and parturition dates, which ranged from 8 February to 15 March (assuming an implantation time of 63 days). Our results are similar to other studies that have reported parturition dates ranging from mid-January to early May in more extreme latitudes. Our results suggest that variation in implantation and parturition dates among populations are likely related to factors affected by latitude such as photoperiod and winter weather severity.