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Reindeer UV Light

December 25, 2011 by staff 

Reindeer UV LightReindeer UV Light, The reindeer of Christmas myth must meet high expectations this time of year — not just hauling heavy loads of gifts over long distances — but also helping navigate from the tundra to the rest of the world.

And even though most real reindeer never pull sleighs through snowy nights, new research suggests that their eyes would be far better suited to the task than Santa’s are. Unlike people, the study found, reindeer can see ultraviolet light — which probably allows them to detect food and predators in a mostly white environment.

The study makes reindeer the first large mammal known to have UV vision. And it raises questions about how animals that are highly specialized to their environments will adapt as their environments change.

“Reindeer are mammals and what we find may be related to humans,” said Karl-Arne Stokkan, an Arctic biologist at the University of Troms? in Norway. “In the view of potential climate change, we have also realized that reindeer may be an important ‘signal-animal’ because of their strong adaptation to an environment believed to suffer the biggest changes.”

Many animals are able to see or respond to ultraviolet light, including some birds, rodents, fish, bees and bats. But UV light is invisible to the human eye and with enough exposure, can even cause damage. Most dangerous are bright, snowy and icy conditions at high elevations or high latitudes, where lots of UV intensity and reflectivity can cause snow blindness in human eyes.

Since reindeer live in the Arctic, where levels of ultraviolet light are at their highest in proportion to other wavelengths, Stokkan and colleagues wondered if the animals might have evolved a way to deal with a world full of ultraviolet radiation. In a lab experiment with LED lights, the researchers first showed that UV light passed right through the reindeer’s cornea and lens into its retina, they reported in the Journal of Experimental Biology.

In human eyes, the lens instead acts as a UV filter, said Marty Banks, a vision scientist at the University of California, Berkeley. That prevents ultraviolet light from reaching the retina, where it can cause damage.

Next, the researchers used anesthetized reindeer to demonstrate that cells in the retina responded electrically to UV signals. Similar tests on other kinds of deer have previously come up negative, Stokkan said.

Ultraviolet vision may be a specialized adaptation to life in the snowy Arctic, the researchers hypothesize. Reindeer eat lichen, which absorb UV light, and they try to avoid being eaten by wolves, whose fur also absorbs the UV spectrum. Being able to see ultraviolet wavelengths, then, may give the animals the ability to see contrasts, helping them find food and avoid predators when surrounded by reflective snow and ice.

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