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Whales return to New Zealand calving grounds

06 Jul, 2011

Source: University of Auckland, Department of Conservation

Using DNA evidence, scientists have discovered that southern right whales appear to be recolonising mainland New Zealand calving grounds from a remnant population in the subantarctic Auckland Islands.

The endangered whales, which were hunted to near extinction in the 19th century, were rarely seen around mainland New Zealand for most of the 20th century. Growing numbers are slowly returning to the coast to give birth and raise their calves.

“With the increase in numbers observed around the Auckland Islands over the last decade, we think that some individuals are rediscovering the former primary habitat around the mainland of New Zealand,” says Professor Scott Baker of The University of Auckland and Oregon State University, who helped initiate the first study of the Auckland Island population in 1995.

The latest findings are based on genetic evidence from small skin samples collected from 707 whales over more than a decade. By comparing the DNA fingerprints of individual whales, the research has confirmed genetic differences between whales around Australia and New Zealand and provides new insight into differences in the recovery of regional populations.

The results support the conclusion that the mainland New Zealand population was wiped out and that the returning whales are from the remnant subantarctic population. It revealed, for the first time, the movement of 7 individual whales between the Auckland Islands and mainland New Zealand. “The 7 whales that have been identified in both the Auckland Islands and the mainland are probably the first pioneers of this recolonisation,” says Dr Baker.

The research has been published in the international journal Marine Ecology Progress Series by scientists from The University of Auckland, New Zealand Department of Conversation (DOC), Australian Antarctic Division, Macquarie University, the Museum of Western Australia and Oregon State University.

“The results confirm the strong connection of right whales to regional calving grounds around Australia and New Zealand as a result of early maternal experience,” says lead author Emma Carroll, a PhD student from The University of Auckland. “This maternal fidelity contributed to the vulnerability of these local populations, which were quickly hunted to extinction using only open boats and hand-held harpoons.”

Maternal fidelity is a kind of cultural heritage passed from a mother to calf during the 1st year of life as they migrate together from calving grounds to feeding grounds thought to be near the subantarctic convergences.

When right whales around mainland New Zealand were wiped out, this heritage seemed to have been lost, slowing the return of whales to their former habitat. Surprisingly, a remnant population that calves in the subantarctic Auckland Islands survived and has shown signs of recovery, with surveys in the 1990s revealing an estimated 1,000 individuals.

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