Adelie penguins are dying of a mysterious disease but scientists in Antarctica don't know what it is.
They've found more than 100 dead penguins near their base, and are worried many more could be suffering from the illness.
The Adelie penguins are one of the most common kind and it's usual to find one or two dead in a colony. But so many dying at once is strange.
The scientists are now taking blood samples from the animals to work out what's wrong.
Infection from scavengers?
Fact File
Adelie penguins
They live in the Antarctic
Have a white ring around the eye
Size: 75 cm
Weight: 3 to 6.5 kg
They eat krill
2 million Adelie penguins worldwide
Keith Reid, an expert in penguins at the British Antarctic Survey, said it's possible Antarctic seabirds or skuas which travel long distances to scavenge may have brought in an infection.
Although they are not an endangered animal, the numbers of Adelie penguins are decreasing, probably because of global warming.
