How an extinction enticed the yellow-eyed penguin

A yellow-eyed penguin. Photo / Thinkstock

A change-over between the yellow-eyed penguin and another penguin species that became extinct around the same time as the moa has been revealed as one of the most rapid biological transition events ever documented.

A team of Otago University scientists has used carbon dating and DNA analysis of archaeological penguin remains to mark the dates when the waitaha penguin became extinct and when the succeeding yellow-eyed penguin moved to the mainland from subantarctic islands.

They showed the waitaha, which was slightly smaller than the yellow-eyed penguin, vanished within 200 years of Polynesian settlement of New Zealand, before 1500AD.

The yellow-eyed penguin, or hoiho -- which today is considered one of the world's rarest penguin species with a population of between 6000 and 7000 -- replaced the waitaha within just a few decades, in the early 1500s.

"Previous research has shown that at the time of human arrival, New Zealand was inhabited by the waitaha penguin," said study author Dr Nic Rawlence, of the university's Department of Zoology.

"Hunting and habitat change apparently caused the extinction of this unique mainland penguin, before the yellow-eyed penguin later arrived here from the subantarctic."

But until now, scientists had little clue when one species went extinct and the other colonised.

Associate Professor Ian Smith, who was also involved in the study, said the rapid biological shift implied a "substantial change" in human pressure around the time of the extinction.

"Interestingly, recent archaeological studies similarly suggest that the Maori population in southern New Zealand declined around 1500 AD, and coincided with a major dietary shift."

The study had parallels with a study published last year that suggested the modern New Zealand sea lion had replaced pre-historic mainland species of sea lion, also thought to have been wiped out by Polynesian settlers.

That research led Otago University scientists to believe the pre-historic sea lion species, which once dominated South Island shores, became extinct as recently as 600 years ago before a lineage previously limited to the waters of the cold subantarctic took their place.

The penguin study, supported by the Marsden Fund and the Allan Wilson, included team members from the Universities of Auckland, Otago, Adelaide and Oslo, as well as Canterbury Museum and the Museum of New Zealand Te Papa Tongarewa.

It was published this week in the leading international journal Quaternary Science Reviews.

An earlier study by University of Otago researchers suggested competition between the two penguin species might have previously prevented the yellow-eyed penguin from expanding north, but environmental changes in the predator population, such as the severe decline of sealions, might have facilitated their colonisation of the South Island.