A winter sighting of killer whales (Orcinus orca) in Antarctic sea ice

A group of killer whales was sighted in open leads well inside Antarctic sea ice during August 1995. This was the first winter sighting of killer whales in Antarctic waters since 1955, and contradicts the view that all killer whales migrate north prior to the winter. A small calf was observed, providing the first evidence of a cetacean species breeding in Antarctic waters. Several potential prey species were also present. The sighting highlights the importance of lead and polynya systems to marine mammals, which probably use them to disperse within the winter sea-ice zone.