Editor, Earth News
The young elephant seal rests alongside another of normal colour (R Reisinger).
A white southern elephant seal has been spotted on a sub-Antarctic beach.
It is the first confirmed sighting of such an animal.
Eared seals, which include sea lions and fur seals are more usually seen sporting unusual colours, but not true seals, a group which includes elephant seals.
Details of the seal, which has creamy white fur but normal brown eyes and nose, have been published in the journal Polar Biology.
"It's quite something in a species which is well-known," says Ryan Reisinger of the University of Pretoria in South Africa, one of the researchers who discovered the animal on Marion Island.
For example, southern elephant seals from many colonies were hunted for decades within the nineteenth and twentieth centuries. In more recent times, scientists have also extensively studied the animals. "Yet this is the first confirmed case of leucism in the species," says Reisinger.
The white seal, a young female, is leucistic, rather than albinistic.
Albino animals lack pigment in just their eyes, or in their eyes, skin and hair, and they inherit the condition. Leucistic animals have little pigment and appear white all over, but with dark coloured eyes.
White fur but normal brown eyes (R Reisinger).
The white seal has a uniformly creamy white coat of fur, with normal dark brown eyes and nose. Its whiskers, eyebrows and fingernails on its flippers are also light coloured compared to the species' usual dark colour.
"To our knowledge, we're the first to provided detailed evidence of such an animal anywhere," says Reisinger.
The research team sighted the white seal on 23 August 2008 on Whale Bird beach on Marion Island, which lies in the sub-Antarctic region of the Indian Ocean. On 30 August, the researchers saw the seal again and got close enough to confirm its leucism, tag it and take a skin biopsy.
They estimate the animal was between one and two years old, and was likely born either on nearby Prince Edward Island or further afield on Iles Crozet.
Reisinger says it's impossible to say precisely how rare the animal is. "We can't put it in terms of one in a million, or one in a hundred thousand."
But he and his colleagues have been monitoring and tagging elephant seals for years on the island without having seen one. While there have been a few rare previous records of lighter coloured elephant seals, none have been confirmed as leucestic.
The young seal resting on Marion Island (R Reisinger).
The researchers were actually on the look out for leucestic Antarctic fur seals when they spotted the white elephant seal.
Antarctic fur seas are usually grey and brown, but numerous white Antarctic fur seals have been spotted before. Last year five unusually coloured Antarctic fur seals were seen on Livingston Island, including one partially leucistic pup that had fur like a tiger's stripes and another piebald individual, the first time such coat patterns have been seen.
In February 2007, researchers also spotted the first known leucestic South American sea lion on the coast of Paso Shag, near the Magellan Strait in Chile.