A scientific team from Italy and another from University of Canterbury have independently proven orca move between the Antarctic and Northland.
Dr Regina Eisert, from Canterbury's Gateway Antarctica, led a team at Scott Base that studied orca as part of a larger research programme on the Ross Sea ecosystem.
Orca in Antarctic waters are known as the type-C species, which is smaller but more common and lives in larger groups than Northern Hemisphere species.
"We wanted to determine whether a decline in the toothfish fishery in the Ross Sea posed a risk to type-C killer whales, including finding out how many there are in the Ross Sea and where they feed," Dr Eisert said.
At the same time, about 360km north of Scott Base, Italian whale experts Dr Giancarlo Lauriano and Dr Simone Panigada fixed satellite transmitters to orca in Terra Nova Bay to determine the whales' movements.