A study of whales in the Gulf of California over the past few years shows that the sea-going mammals carry blisters and other damage typically associated with the skin damage that humans suffer from exposure to the ultraviolet radiation. That makes it yet another threat for the already endangered animals to worry about.
Whales would be particularly vulnerable to sunburn in part because they need to spend extended periods of time on the ocean's surface to breathe, socialize, and feed their young. Since they don't have fur or feathers, that effectively means they sunbathe naked.
As Laura Martinez-Levasseur, the study's lead author, put it: "Humans can put on clothes or sunglasses - whales can't."
Martinez-Levasseur, who works at Zoological Society of London, spent three years studying whales in the Gulf of California, the teeming body of water which separates Baja California from the Mexican mainland.
Photographs were taken of the whales to chart any visible damage, and small samples - taken with a crossbow-fired dart - were collected to examine the state of their skin cells.
Her study, published in the Proceedings of the Royal Society B, seemed to confirm suspicions first raised by one of her whale-watching colleagues: The beasts were showing lesions associated with sun damage, and many of their skin samples revealed patterns of dead cells associated with exposure to UV radiation.
As with humans, the lighter-skinned whales seemed to have the most difficulty dealing with the sun. Blue whales had more severe skin damage than their darker-skinned counterparts, fin whales and sperm whales, even though the latter spend bigger chunks of time at the surface.
So far, there were no indications of skin cancer among the whales studied, although Martinez-Levasseur, who is also a Ph.D. student at Queen Mary, University of London, noted that only tiny samples were taken of the massive animals.
She said one of her next projects will be to examine how well whales' cells hold up under the increased UV radiation - and whether whales' pigmentation darkens as a result of their time spent out in the sun.
In other words, she wants "to be able to see if they're tanning."