Why Don’t Snakes Get Sunburned?

Jim asks: Do non-human animals ever get sunburned? Why don’t things like snakes and other cold blooded animals seem to get burned even though they lay in the sun all day?

California-KingsnakeWithout a protective coating of feathers, fur or scales, pretty much any animal with exposed skin can get a sunburn; luckily, most animals have adapted methods of avoiding the sun and mitigating the damage.

Farmers have long known that naked animals, like freshly shorn sheep and domesticated pigs (who’ve had their thick coating of back hair bred out of them), can get a sunburn. In fact, although uncommon, even light-furred and hairless dogs and cats have been known to burn.

Likewise, naturalists have observed burns from ultraviolet radiation on elephants and rhinoceroses, and in fact, even whales, fish, amphibians and dolphins occasionally get a burn from the sun.

In research published in the Proceedings of the Royal Society in 2010, scientists reported that certain whale species, notably the relatively light-skinned blue whale, not only would suffer from sunburn, but that the rate of sunburn in the marine mammals was increasing over time. The researchers theorized that ozone layer loss and thinning cloud cover could potentially be to blame for the increase.

Those same scientists also found that, even though sperm whales spend significantly more time on the surface in between dives (7 to 10 minutes) when compared with blue whales (about 2 minutes), the darker sperm whales were far less likely to suffer from sunburn. Further research also revealed that the sperm whales’ skin has a protective protein that inhibits UV cellular damage.

Notably, although the blue whales’ incidences of sunburns were increasing, the scientists did find evidence that the species is able to tan, so sun exposure did not always result in such damage.

Likewise, many land animals have also adapted methods of protection from the sun. For example, pigs and rhinoceroses wallow in mud, as do elephants who are also known to seek out shade, toss dirt and sand on their backs and create protective shadows for their little ones.

Hippos secrete an oily, pinkish-red liquid, particularly around their ears and faces (the only parts typically above the water’s surface for any length of time) that absorbs ultraviolet light and also is, apparently, naturally antibiotic.

As for snakes and other reptiles that at times bask in the sun, their inner epidermis is protected from UV rays via their scales, which also function to help retain moisture underneath, among other things. For these animals, they would typically die from overheating before any threat of sunburn became a problem.

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Bonus Facts:

  • A review published in JAMA Dermatology in January of 2014 showed that exposure to the UV wavelengths associated with indoor tanning beds account for nearly twice as many skin cancer diagnosis as smoking does lung cancer in the United States-  about 400,000 annually for tanning beds, compared to 200,000 from smoking.  Further, even just one tanning bed session increases your risk of getting melanoma- the deadliest form of skin cancer- by 75%. This is why the American Medical Association, the American Academy of Pediatrics, the American Academy of Dermatology, the Skin Cancer Foundation, and the World Health Organization have all called on every state to ban children under 18 from using tanning salons.
  • Skin cancer is the most common form diagnosed in the United States, outpacing the incidence of colon, breast, lung and prostate combined. Nearly 90% of non-melanoma skin cancers are correlated with sun exposure.
  • In 2011, more than 70,000 people (over 41,000 men and 29,000 women) in the U.S. were diagnosed with melanomas, from which more than 12,000 died. In total, each year almost 5 million people are treated in the United States for all skin cancers. It is estimated that 1 in 5 Americans will develop skin cancer at some point in their lives.
  • The rarely fatal basal cell carcinoma is the most commonly diagnosed skin cancer, with nearly 3 million found each year.
  • The American Academy of Dermatology (AAD) recommends that everyone (regardless of heritage and pigmentation) use a sunscreen whenever they will be outdoors for any length of time (even if it’s cloudy). Broad-spectrum protection for both UVA and UVB is also recommended, and it should be at least of a Sun Protection Factor (SPF) of 30 and also water-resistant. (See: The Meaning of SPF) Sunscreen should be re-applied every two hours, and after exposure to water (either via swimming or sweating). Furthermore, even with sunscreen, dermatologists caution that people should still wear protective clothing and seek shade whenever possible.
  • All that said, sunscreen use combined with more sedentary, indoor lifestyles has led to a crisis of vitamin D deficiency in the United States. According to the Centers for Disease Control (CDC), one-third of Americans are either seriously deficient or at-risk, and some studies have even found that 70% of breastfed babies were lacking in vitamin D. In addition, people with darker skin, including African Americans and Hispanics, have been found to be two to three times more likely to be deficient (due to less absorption) than lighter-skinned folks. Low vitamin D increases the risk of colon and breast cancer as well as heart disease, and some studies have indicated that 13% of deaths in the U.S. are associated with insufficient vitamin D3. Many believe vitamin D deficiency also contributes to the development of metabolic disease, obesity, high blood pressure and other infections. So is it a choice between skin cancer and the health problems associated with vitamin D deficiency?  Not really, as there’s a simple solution- take a good quality vitamin D supplement daily. How much should you be getting? The Institute of Medicine of the National Academies recommends that all people between 1 and 70 years should have an intake 600 IU of vitamin D each day (and 800 IU for those over 70).
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