Review of killer whale (Orcinus orca) ice entrapments and ice-related mortality events in the Northern Hemisphere

Abstract

In January 2013, a group of killer whales (Orcinus orca) was discovered in an ice entrapment in eastern Hudson Bay, Canada. The whales escaped the entrapment after several days, which ended the discussion on response options. The event did, however, highlight the need for a better understanding of killer whale entrapments to guide future responses. We conducted a literature review of ice entrapment and ice-induced stranding mortality events for killer whales in the Northern Hemisphere and identified 17 events dating from 1840 to 2013, ranging from a single whale to more than 20. Ice entrapments occurred in both pack ice (mobile ice) and fast ice (ice which forms and remains fast along the coast), with most records (70 %) coming from midlatitude regions with seasonal ice cover (e.g., Sea of Okhotsk and eastern Canada). Most events resulted in mortality, and time to mortality depended on ice conditions with whales surviving longer in fast-ice entrapments, where ice is more stable than in mobile ice.