This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A new University of Otago—Ōtākou Whakaihu Waka study reveals two vastly different life courses for one of Aotearoa New Zealand's least-studied penguin species. In a study published in the journal PLOS ONE, researchers found that erect-crested penguins are split into two populations on sharply divergent paths—one that has been stable for at least 25 years and the other that has lost more than 40% of its birds in the past 30 years.
Thomas Mattern of the Tawaki Project—composed of researchers based in Otago's departments of zoology and marine science—in collaboration with the Antarctic Research Trust and the Global Penguin Society. Mattern says erect-crested penguins breed only on the Bounty and Antipodes islands, two remote groups about 800 km (500 miles) southeast of the South Island. Between 2022 and 2024, researchers used drones to photograph and count every breeding colony across both island groups—the first time this has been done for the entire species.
"The results overturn a long-standing assumption," Mattern says. "The tiny Bounty Islands, at just 50 hectares (124 acres), were found to hold almost as many breeding pairs (about 27,800) as the Antipodes Islands (about 29,800), even though the latter group is 40 times larger and has historically been considered the species' stronghold." More strikingly, the two populations are moving in opposite directions. "A comparison of the new counts with historical records going back to the mid-1990s shows that the Bounty Islands population has remained essentially unchanged for at least 25 years.
The Antipodes Islands population, by contrast, has declined by more than 40% since 1995." Mattern says there are compounding factors for this, such as predators, weather and migration routes. "As Antipodes colonies have shrunk over recent decades, the collective defense they once provided against the native subantarctic bird, the skua, a natural predator of eggs and chicks, has weakened, allowing predation losses to increase and colonies to fragment further." Co-author Dr. Klemens Pütz, of the Antarctic Research Trust, says erect-crested penguins became more frequent targets after the demise of the eastern rockhopper penguin species.
Rockhopper numbers crashed "catastrophically" over the second half of the 20th century, mirroring trends elsewhere across the species' Southern Ocean breeding range, likely due to ocean warming, leaving fewer than 1,000 breeding pairs on the Antipodes Islands. "As rockhoppers disappeared, skuas may have turned to erect-crested penguin eggs and chicks instead," Pütz says. Increasingly severe storms, consistent with broader climate trends in the Southern Ocean, have triggered landslides that further fragment colonies and put them at risk, while differences in the penguins' ocean habitat and migration routes likely added to the problem.
Mattern says Antipodes birds travel far into the Antarctic Polar Frontal Zone outside the breeding season, while birds from the Bounty Islands stay close to more sheltered, potentially more productive waters near the breeding sites. Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly. Researchers have dubbed the situation "Schrödinger's Penguin," after the well-known thought experiment in which a cat sealed in a box is imagined to be simultaneously alive and dead until someone opens the box and checks.
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