black penguin
© Andrew Evans/National Geographic/BarcroftThe rare melanistic penguin, photographed by Andrew Evans on the sub-Antarctic island of South Georgia
The penguin, believed to be suffering from a condition known as melanism, was spotted on Fortuna Bay, a sub-Antarctic island of South Georgia, about 860 miles off the Falklands.

A group of travellers had travelled to the island to watch local wildlife and one of the group, Andrew Evans, took this picture of the penguin, one of several thousand.

"Observing this black penguin waddle across South Georgia's black sand beach revealed no different behaviour than that of his fellow penguins. In fact, he seemed to mix well," he wrote on a National Geographic blog.

"Regarding feeding and mating behaviour there is no real way to tell, but I do know that we were all fascinated by his presence and wished him the best for the coming winter season."

Biology experts say that because black penguins are particularly rare there is very little research discussing the subject. Melanism is however, common on other animal species such as squirrels.

It is estimated that about one in every 250,000 penguins shows evidence of the condition.

Ecology and Evolutionary Biology expert Dr Allan Baker, from the University of Toronto, said the Antarctic penguin was black because it had lost control of its pigmentation patterns.

After being shown the pictures by National Geographic, Dr Baker, also the head of the Department of Natural History at the Royal Ontario Museum, described them as "astonishing".

"I've never ever seen that before," he told the magazine.

"It's a one in a zillion kind of mutation somewhere. The animal has lost control of its pigmentation patterns. Presumably it's some kind of mutation."

According to the Encyclopaedia Britannica, the condition is the darkness in an animal's skin, feathers, or fur is acquired by populations living in an industrial region where the environment is soot-darkened. It can be gene related

It does, however, mean that the probability that its members will survive and reproduce is enhance.

The condition evolves over the course of several generations.

But due to being lighter in colour, they become more conspicuous to predators.