Polar bears (Ursus maritimus) mating during late June on the pack ice of northern Svalbard, Norway

Abstract

Polar bears are seasonal breeders and typically mate from late March to early May. Implantation is, however, delayed until autumn, which can allow plasticity in the date of mating. As for other seasonal breeders, a rapid return to estrus after the loss of dependent offspring can be expected, even into the summer. A few earlier observations and dissections of dead animals suggest that polar bears are able to mate in summer. We report on a mating incident on 29 June 2014, the first documented mating this late in the season among wild polar bears. The female had lost her dependent cub during the period prior to the mating event. We speculate that she lost this cub late in the mating season, entered estrus and successfully mated in late June.

• Polar bear
• mating season
• mating behaviour
• Svalbard
• Arctic

Acknowledgements

We thank Kevin Morgan, who first spotted the mating bears, Frank S. Todd and Lauren Farmer for the photographic documentation and Susan Adie, the Expedition Leader for G Adventures, for allowing us the opportunity to thoroughly document this unique event. The careful approach of the ship by Captain Giovanni Biasutti allowed us to observe this event without disrupting the behaviour of the bears. We also thank Magnus Andersen and Rupert Krapp for their involvement in the capture–recapture work that provided reproductive and space-use data for the female bear. The governor of Svalbard and the Norwegian Animal Health Authority granted approval for this work.