Magellanic penguin chicks in Argentina have a new killer to fear -- death by climate change.
The downy chicks were already vulnerable to predation and starvation in the first few weeks of their lives, but now they are threatened by increasing rainstorms caused by changing weather patterns.
"Climate change is a new mortality factor," said Dee Boersma, a conservation biologist at the University of Washington. "It didn't use to kill these penguins and now it does."
Boersma and her team have been studying penguins for 28 years at Punta Tombo on the Atlantic side of Argentina -- home of the largest Magellanic penguin colony in the world. Each year 200,000 penguins stay there from September to February to incubate their eggs and raise their young. Boersma describes the gathering as "one of those spectacles of nature."
Over the course of the 28-year study, Boersma found that an average of 65% of the penguin chicks died per year. The most common killer was starvation, which was responsible for 40% of the total chick deaths. But in 1991 an unusual rainstorm in the normally arid area killed the same number of chicks as starvation and predation combined. In 1999, rain killed as many chicks as all other causes of death combined.
Not all rainfall is deadly to chicks, but prolonged, big storms can be. Baby penguins are covered in a soft down that keeps them warm, but only if it stays dry.
"You have to realize that most species of penguins live in deserts," Boersma told the Los Angeles Times. "As long as they are dry, they are nice and warm, but as soon as they get wet the down doesn't insulate them anymore. And then, just like humans, it doesn't need to be freezing for them to die of hypothermia."
Younger chicks actually have a better chance of surviving a rain than older chicks who have not yet fledged because they are still small enough to be protected from the rain by their mom or dad. The researchers found that chicks between the ages of 9 and 23 days were most likely die in a storm. As they get older, their waterproof feathers come in and they are no longer vulnerable.
On average, Punta Tombo gets about 4 inches of rain during the six month period of the Magellanic penguin breeding season. But that seems to be changing.
"Climate models show it is getting wetter, and we show it has gotten wetter," said Boersma. "Not every storm kills chicks, but the big storms do."
Boersma said she was not surprised by the findings in her study, published this week in the journal Plos One. "When you work on anything for 28 years there shouldn't be a lot of surprises," she said. But what does surprise her is that people feel there is no way to help these penguins.
"It is not all over and done," she said. "What these penguins need is a marine protected area so they can have more food close to their colony. The major cause of death of these chicks is still starvation."
Just a little background on the Magellanic penguins: They are a medium-sized penguin standing about 15 inches tall and weighing in at 10 pounds. The males sound like a braying donkey when they vocalize. You can see pictures of the penguins both wet and dry, and alive and dead, in our gallery above.
Follow me on Twitter for more cool science stories from around the world.