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Magellanic penguins were decimated by an extreme heatwave

Climate change is causing increasingly more heatwaves all over the globe, affecting humans, as well as wildlife and various ecosystems. A new study led by the University of Washington (UW) has investigated the unprecedented heat mortality of Magellanic penguins (Spheniscus magellanicus) during the severe heatwave of January 19, 2019 at Punta Tombo, Argentina, when temperatures rose to an all-time record of 44°C.

According to the researchers, this massive heatwave killed at least 354 penguins in a single day, out of which nearly three quarters (264) were adults. Most of them died of dehydration. “This extreme event fell near the tail end of the breeding season for Magellanic penguins, so it killed a large number of adults, as well as chicks,” said study lead author Katie Holt, a doctoral student in Biology at UW. “It’s the first time we’ve recorded a mass mortality event at Punta Tombo connected to extreme temperatures.”

Holt and her colleagues found 27 percent of adult penguin corpses lying along paths leading from the breeding colony to the ocean. Since penguins have glands that can filter salt out of water, the researchers believe that the victims were desperately trying to reach the ocean to quench their thirst. Travelling from the colony to the ocean can take an adult penguin up to 40 minutes to complete – a task which proved impossible during that heatwave.

“Any mass die-off like this is a concern,” said Holt. “But what is most concerning about heat-death mortality is that it has the potential to kill a lot of adults. The population viability of long-lived seabirds — like Magellanic penguins — relies on long lifespans. Adult Magellanic penguins can live more than 30 years, so they typically have many opportunities to successfully raise chicks. If we’re losing large numbers of adults from a single event like this, that’s a major concern.”

At least eight out of ten adults that died were male. However, this likely reflects the high prevalence of male Magellanic penguins at Punta Tombo (about three males for each female), rather than a gender differential survivability in extreme heat.

Global warming is expected to produce increasingly more extreme weather events all around the Earth, endangering many species. And while animals are often surprisingly adaptable, the severity of such events may impede their struggles to survive.

“Penguins could have the ability to cope, like moving breeding sites,” said Holt. “But it will take time to investigate whether those adaptations are effective.”

The study is published in the journal Ornithological Applications.

By Andrei Ionescu, Staff Writer

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