Tourists were astonished to see the “blonde penguin” at the edges of one of the South Shetland Islands while on a National Geographic cruise: Journey to Antarctica. The penguin resembles an albino but it appears to have a condition known as isabellinism, according to P. Dee Boersma, a penguin expert.
According to a study published in 2009 on the journal Marine Ornithology, isabellinism is a genetic mutation condition that dilutes pigment in the feathers of affected penguins. The dark colors of the bird lighten uniformly and turn the animal pale brown or grayish yellow. Isabelline penguins are not albinos.
The terms “Isabellinism” and “leucism” represent separate conditions technically, but sometimes the words are used interchangeably. Albinism is when an animal does not produce any melanin throughout its entire body while Leucism is a type of mutation that prevents any melanin from being produced in the feathers. Boersma says that many of the penguin species have a few penguins that have this color pattern but they are rare.
Scientists have for example observed most isabellinism cases in Gentoo penguins that can be found in the Antarctic Peninsula. The lowest incidences are with the Magellanic penguins that live on the South American coasts.
While in the ocean, penguins use their black backs to camouflage themselves from predators and prey that swim above. Boersma suspects that isabellinism would affect the survival of the South Shetland penguin although no study has been done on the subject.