At Least Some Penguins Benefited From Record Antarctic Sea Ice Loss

At Least Some Penguins Benefited From Record Antarctic Sea Ice Loss
Adélie penguins in Lützow-Holm Bay, Antarctica, enjoy easy access to food and increase body weight and breeding success in ice-free summer. (Photo: Yuuki Watanabe, National Institute of Polar Research, Japan)

Antarctica’s sea ice has crashed in recent years. It’s nothing to celebrate, but apparently some Antarctic penguins are loving it. A new study out Wednesday found that a group of Adélie penguins actually thrived during a period of sea ice loss. Don’t get too excited, though. This sea ice loss doesn’t affect all penguins the same.

The study, published in Science Advances, zoomed into the breeding season in 2016 through 2017 along Lützow-Holm Bay in East Antarctica. That year, the region saw tremendous sea ice loss. In fact, the continent set a record low in 2017. Researchers found that, to their surprise, the penguins saw increased body mass, chick growth rates, and breeding success this season compared to the other three ranging from 2010 to 2013.

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“It turns out that these penguins are happier with less sea-ice,” lead researcher Yuuki Watanabe at the National Institute of Polar Research in Tokyo, said in a statement. “This may seem counter-intuitive, but the underlying mechanism is actually quite simple.”

The group of 175 birds was able to forage more easily with less sea ice, swimming more to search for food instead of walking. Penguins are faster swimming than walking. As a result, the penguins were able to spend more time foraging while expending less energy. During years of increased ice cover, the penguins were forced to walk farther in search of cracks in the ice where they can dive to forage for krill and fish. Without the ice, the birds were free to dive into the water right in front of their nests. The penguins wound up saving 3.2 to 7.9 hours on the shorter duration trips while covering up to 4.8 kilometres more distance than they would’ve with more ice.

All this made a measurable difference in the penguins’ health. Females saw a 5% to 16% higher body mass while males saw 7% to 17% more. Chicks, on the other hand, grew 34% to 52% more compared to the seasons with higher ice cover. Previous studies had found varying impacts of sea ice loss to penguins, but none had used the types of technologies — GPS, cameras, and accelerometers — in the new study to tease out the mechanisms of what’s driving the difference in behaviour.

“The bonus in this paper is that technological advances (GPS tags, dive depth recorders, etc.) actually show us what aspects of the ecology of Adélies are affected by more optimal sea ice conditions,” Bill Fraser, the president and lead investigator at the Polar Oceans Research Group who has also studied these dynamics in Adélie penguins but not as part of this study, wrote to Gizmodo in an email. “This is really the most unique/novel aspect of this paper; in other words, the instrument-generated data that actually shows how Adélies respond to sea ice.”

A happy and healthy family. (Photo: Yuuki Watanabe, National Institute of Polar Research, Japan) A happy and healthy family. (Photo: Yuuki Watanabe, National Institute of Polar Research, Japan)

Through these technologies, the team of scientists from the National Institute of Polar Research in Tokyo could track foraging trips, categorise swimming versus walking behaviours, and estimate how much prey the penguins caught during their dives. However, the paper doesn’t explain why Adélie penguin populations in warmer parts of the Antarctic Peninsula don’t fare as well with less ice. The authors hypothesise in the paper that prey availability and energy expenditure might have to do with that. The way Fraser sees it, this paper doesn’t really offer any good news. In fact, it shows just how sensitive these creatures are to a changing climate.

“Adelies are not safe anywhere as long as the Earth continues to warm,” he told Gizmodo.