New study reveals King penguins keep an ear out for predators even when asleep

King penguins can distinguish between the sounds of dangerous predators and harmless noises even while sleeping, a new study has found.

The study showed that these birds react differently to the sounds of predators than to non-predators and other sounds.

Both adult and juvenile king penguins are prey to large predators like orcas and giant petrels. Even huge non-predator elephant seals can crush penguins to death with their bulky passage.

In an environment like this, king penguins who are exhausted after long diving sessions must constantly keep an ear out for incoming threats.

"When we played single tones to sleeping penguins, they woke up with little reaction. However, playing them the calls of orcas or skuas caused them to wake up and flee," said Tessa Abigail van Walsum, a Ph.D. student at the University of Roehampton in the UK.

Penguins also had strong reactions to some non-predator sounds, said van Walsum.

"The sounds of approaching elephant seals rang big alarm bells for the penguins. A recording of simple white noise had an unexpectedly strong effect, likely because it sounds much like an incoming wave on the beach," she said.

Notably, playing them the sound of unfamiliar predators, such as a dog's growl, got little reaction when they awoke.

The ability of these birds to respond differently upon waking up suggests that they might sleep with just one-half of their brain, while keeping a close watch with the other half similar to some migratory birds - essentially 'keeping an eye open'.

This research helps us to understand the survival strategies of king penguins in their natural habitats.