Southern right whales hunted to near-extinction in the 19th century appeared to be re-colonising waters off New Zealand’s two main islands, scientists said Monday.

A study by Auckland University, Oregon State University and other institutions found the whales were returning to their old New Zealand calving grounds as their numbers increase off the sub-Antarctic Auckland Islands.

Southern right whales were hunted intensively off New Zealand and Australia in the 19th century. The species was given legal protection by the League of Nations in 1935 but was subject to illegal whaling in the 1950s and 1960s.

The study published Monday concluded the mainland New Zealand population was wiped out and DNA samples taken from the returning whales showed they come from the 1,000 left around Auckland Island.