Tests show Arctic reindeer 'see in UV'

They say tests on reindeer showed that the animal does respond to UV stimuli, unlike humans.

The ability might enable them to pick out food and predators in the "UV-rich" Arctic atmosphere, and to retain visibility in low light.

Details are published in the The Journal of Experimental Biology.

Seeing predators

UV light is invisible to humans. It has a wavelength which is shorter (and more energised) than "visible" light, ranging from 400 nanometres down to 10nm in wavelength.

The researchers first established that UV light was able to pass through the lens and cornea of the reindeer eye by firing light through a dissected sample. The tests showed that light down to a wavelength of about 350nm passed into the eye.

They then sought to prove that the animals could "see" the light, by testing the electrical response of the retina of anaesthetised reindeer to UV light.

"We used what is called an ERG (electroretinography), whereby we record the electrical response to light by the retina by putting a little piece of gold foil on the inside of the eyelid," co-author Professor Glen Jeffery of University College London told BBC News.

The tests showed that photoreceptor cells or "cones" in the retina did respond to UV light.

"If you're a bumblebee, you wouldn't think much of what this animal is doing because it's seeing in what's called 'near UV' (about 320 to 400nm), but that's still very high energy stuff."

The researchers believe UV vision could enable the reindeer to distinguish food and predators in the "white-out" of the Arctic winter and the twilight of spring and autumn.

Lichen, on which the animal feeds, would appear black to reindeer eyes, they say, because it absorbs UV light. The animal's traditional predator, wolves, would also appear darker against the snow, as their fur absorbs UV light; Kazinform cites BBC News.

To learn more go to www.bbc.co.uk