A new study shows that a heatwave in January 2019 was responsible for the death of Magellanic penguins in Argentina.
Named after Portuguese explorer Ferdinand Magellan who spotted them in 1520, the Magellanic penguins are predominantly found in South America and the Falkland Islands. One of their largest breeding colonies is in Argentina, where the 2019 heatwave occurred during the austral summer.
On January 19, temperatures in a shady spot at Punta Tombo, along Argentina’s southern coast, reached 44°C (111.2°F), the highest ever recorded since co-author P. Dee Boersma began studying this population of Magellanic penguins in 1982. Shortly thereafter, University of Washington scientists surveyed the population, and discovered that 354 adults had perished.
“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,” says lead author Katie Holt. “It’s the first time we’ve recorded a mass mortality event at Punta Tombo connected to extreme temperatures.”
Nearly 75 percent of the dead penguins were adults and postmortem analyses suggest they were dehydrated. Multiple penguins were in a prone position with their mouths open – a common posture used for a cooling off. And, many of the corpses were found along a path between the breeding colony and the ocean, where penguins can access water and use specialized glands to filter salt from seawater. This one-kilometer path can take nearly 40 minutes for a Magellanic penguin to complete.
Temperatures during this time of year can range from approximately 50 – 105°F, and a previous spike to 109°F in the shade did not result in such a mortality event. However, it seems that this single temperature monitor does not represent conditions across the breeding colony because some sections saw virtually no fatalaties, which indicates microclimates may exist and create refuges for these penguins.
“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.”