The yellow-eyed penguin’s foraging habits provide insight into protective measures

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New research into the behavior of yellow-eyed penguins on Stewart Island could help prevent them from becoming extinct.

Stewart Island is home to about a quarter of all breeding yellow-eyed penguins in their mainland range.
Photo: AFP

Yellow-eyed penguins are endangered and Rakiura’s population has declined significantly over the past 15 years – from around 54 pairs in 2008/2009 to 44 during the last breeding season.

Thor Elley, a postgraduate student at the University of Otago, tracked the behavior and foraging habits of 19 adult yellow-eyed penguins at three sites on Stewart Island, including Port Pegasus, Paterson Inlet and Codfish Island.

The penguins were fitted with GPS dive data loggers during the 2020/21 breeding season, to track movements and diving behavior, which resulted in a total of 25,696 dives being recorded during 91 trips foraging.

The study recently published in the journal Biology, shows that although foraging areas and travel lengths were significantly different between sites and depended on a range of factors, the behavior of birds from the same site was surprisingly predictable and consistent.

Elley said the predictability gives a robust estimate of the size and shape of ideal marine protection measures, and shows that managing local fisheries could reduce overlap with where penguins forage.

Stewart Island is home to around a quarter of all breeding yellow-eyed penguins in their mainland range, so the loss of an adult could have a significant impact on the population.

“Fishing-related mortality can have a massive flux effect during breeding seasons, such that if one adult dies, the two dependent chicks usually starve and the surviving breeding partner will likely skip the next breeding season.”

Fixed net restrictions in place adjacent to the South Island reduce the risk of entanglement and death in the four nautical mile exclusion zone, but no fixed net restrictions are in place for the Stewart Island and its outer islands.

Elley said set-net effort peaked in the summer, coinciding with the breeding season for yellow-eyed penguins.

“These fisheries overlap with the preferred feeding grounds of yellow-eyed penguins and current net fishing practices in both Pegasus Inlet and waters along the coast could very likely mean local extinction unless we don’t. rethink coastal fishing practices.”

Study co-author and supervisor Professor Phil Seddon said the new technology used in the study has highlighted its potential to increase our understanding of species behavior.

“Not so long ago, the marine distribution of yellow-eyed penguins was largely a mystery to us, but now, with miniature tracking devices, we are getting a detailed picture of their marine distribution, an area where penguins spend most of their time.”

“A better understanding of the foraging range and foraging behavior of yellow-eyed penguins will inform management, marine spatial planning and other measures that can reduce the risks facing this iconic living treasure. “

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