(Phys.org) —Scientists have shown that mainland New Zealand has become an increasingly important winter habitat for southern right whales – a population hunted to near extinction in the 19th century – and members of the public have played a critical role in the research.

"This endangered whale now seems to be a regular visitor to mainland of New Zealand" said lead author Dr Emma Carroll from The University of Auckland "For the first time we have documented southern right whales returning to the mainland, including females returning with their calves in different years."

The findings suggest that mainland New Zealand could become an important habitat for mothers and calves and perhaps larger social groups. Between 2003 and 2010, for instance, 28 mother-calf pairs were seen in the area, compared with only 11 sightings from 1991-2002 and none between 1976 and 1991.

New Zealand's coastal waters were once the seasonal home of tens of thousands of southern right whales. However extensive whaling saw the whales all but disappear from around the mainland, with few sightings for most of the twentieth century.

In recent decades a remnant population was found around the sub-Antarctic islands and members of this growing population now appear to be re-colonising mainland New Zealand.

"We now have photo-ID matches confirming that the same individuals are moving back and forth between the Auckland Islands and the mainland," said co-author Dr Will Rayment from the University of Otago.

"This is great news because the population at the Auckland Islands is recovering strongly. Hopefully we'll see more of these whales around the mainland in the future."

"The public plays a key role in supporting this research by reporting sightings to 0800 DOCHOT (0800 36 24 68)," says Dr Laura Boren from the Department of Conservation (DOC). "Their reports enable our staff to obtain samples from opportunistic sightings, in numbers that wouldn't otherwise be possible. This has been a great piece of collaborative work to monitor the re-colonisation of an endangered species".

To monitor the whales' numbers around mainland New Zealand DOC launched a public awareness campaign in 2003, encouraging people to report sightings. This led to a collaborative research project involving researchers from The University of Auckland, University of Otago and Oregon State University.

The latest findings are based on these sightings data, and whales individually identified from photographs of natural markings and/or DNA profiles from small samples of skin. The research has been published in the current issue of Marine Mammal Science.

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