Ice entrapment mortality may slow expanding presence of Arctic killer whales

Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic during the summer months. Increasing killer whale sightings throughout the region, and incursions into areas where they have not historically been observed, have been linked with declining sea ice, which has raised questions about the potential ecological impacts of a greater killer whale presence in the Arctic. Here we report on four killer whales that died of starvation after overwintering in southeastern Hudson Bay. This incident is similar to two other reported killer whale ice entrapments in Hudson Bay in 2011 and 2013, which together exceed the incidence of such events over the previous century. The six confirmed, and up to 16 more assumed, deaths due to ice entrapments over the past decade almost certainly represent significant levels of mortality for the population(s) of killer whales in the Canadian Arctic. Ice entrapments of naive killer whales exploring new Arctic territory may therefore offer a natural check on range expansions in the region, particularly in convoluted inland bays and inlets into which they pursue previously inaccessible prey, but fail to exit prior to ice formation.