Grim future for Peninsula penguins forecast

A parcel of  yellow-eyed penguins gathers on an Otago Peninsula beach. Photo by Craig Baxter.
A parcel of yellow-eyed penguins gathers on an Otago Peninsula beach. Photo by Craig Baxter.

Scientific modelling predicts a grim future for Otago Peninsula's endangered yellow-eyed penguins.

Modelling by University of Otago scientists has shown under the best-case scenario the peninsula population would be in slow decline; under the worst, it would be in steep decline.

Associate Prof Phil Seddon, of the wildlife management programme, said the research, led by Thomas Mattern, surprised scientists as indications were that even without catastrophic events, such as last year's mass mortality, something was keeping adult survival rates from increasing.

''We can't just address catastrophic events and assume everything else is fine.''

The modelling used data gathered on Otago Peninsula from 1980 to 2008, although the most intensive monitoring data available was from 1991 to 2005.

It showed in the good years - 1991 to 1995 - adult survival from one season to another was as low as 94%; ''what you'd want to see in a long-lived seabird''.

In the bad years - 1997 to 2005 - survival dropped to 80%-87% and in the catastrophic years - 1996, 1998 and 2001 - it dipped to as low as 64%.

When the modelling was done using the ''best case'' figures it indicated a slow decline but using present survival rates plus a catastrophic event which more closely resembled actual survival it showed the population would be in ''steep decline'', he said.

A decline in intensive monitoring meant data from 2005 was not able to be used and the lack of similar data for other populations in North Otago and the Catlins meant the same modelling could not be done for them.

''A strong recommendation from this was that we really need good information to assess how the population is doing.''

To put the data in context, the scientists also ran data from seabird sciencefounder Lance Richdale's monitoring on the peninsula from 1937 to 1949 through the models and found survival then was similar to the ''best case'' during 1990-95.

''The population appeared fairly stable back then and survival was high, which matches what Richdale recorded.''

However, since that time something had happened to reduce adult survival.

''Something is happening in the background ... the adult population isn't doing as well as it should.''

Other university modelling indicated 81% of fledglings died before they were 2 years old. Fewer than 10% of fledglings survived to breed successfully and only half of those produced fledglings that also survived and bred successfully, he said.

''So the population is being sustained by only a small proportion of breeding birds, with many breeding attempts by many birds not contributing anything to future generations.''

It was hard to pinpoint what the background cause could be as it most likely involved the penguins' time at sea, Prof Seddon said.

Recent work by researchers, the Department of Conservation and the Yellow-eyed Penguin Trust had focused on their land-based habitat and increasing breeding opportunities. Threats could include climate change, increasing predators and fishing, or together they could add up to a problem.

Finding out what happened to penguins off-shore was harder, as the technology to do this was ''not quite there''.

''We've just got to hope we have penguins left by the time we do.''

Scientist Ursula Ellenberg also contributed to the research.

Yellow-eyed Penguin Trust general manager Sue Murray said the outlook was concerning, especially given the huge conservation effort which had gone in to getting the population to where it was now.

The information would inform the trust in its decisions on where to concentrate its conservation efforts and highlighted the need to better understand issues such as penguins' interactions with fishing vessels.

rebecca.fox@odt.co.nz

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