Bright eyes: Study finds reindeers' eyes change colour with Arctic seasons

Oct 29, 2013
A wild reindeer with velvet covered antlers. Part of the southern herd on the island of South Georgia in the South Atlantic. Image: Wikipedia

Researchers have discovered the eyes of Arctic reindeer change colour through the seasons from gold to blue, adapting to extreme changes of light levels in their environment and helping detect predators.

The Biotechnology and Biological Sciences Research Council (BBSRC) funded team from UCL (University College London), and the University of Tromsø, Norway, showed that the colour change helps reindeer to see better in the continuous daylight of summer and continuous darkness of Arctic winters, by changing the sensitivity of the to light.

Arctic reindeer, like many animals, have a layer of tissue in the eye called the tapetum lucidum (TL) which lies behind the retina and reflects light back through it to enhance night vision.

By changing its colour the TL reflects different wavelengths of light.

In the bright light of summer the TL in Arctic reindeer is gold, similar to many other mammals, which reflects most light back directly through the retina.

However by it has changed to a deep blue which reflects less light out of the eye.

This change scatters more light through photoreceptors at the back of the eye, increasing the sensitivity of the retina in response to the limited winter light

The team believes this would be an advantage in the prolonged murk of winter, allowing reindeer to more easily detect moving predators and forage.

This video is not supported by your browser at this time.

Lead researcher Professor Glen Jeffery from UCL, said: "This is the first time a colour change of this kind has been shown in mammals. By changing the colour of the TL in the eye reindeer have flexibility to cope better with the extreme differences between light levels in their habitat between seasons.

"This gives them an advantage when it comes to spotting predators, which could save their lives."

The colour change may be caused by pressure within the eyes. In winter pressure in the reindeers' eyes is increased, probably caused by permanent pupil dilation, which prevents fluid in the eyeball from draining naturally. This compresses the TL, reducing the space between collagen in the tissue and thus reflecting the shorter wavelengths of the blue light common in Arctic winters.

Previous work from Professor Jeffery and Norwegian colleagues from Tromso had shown that Arctic eyes can also see ultraviolet, which is abundant in Arctic but invisible to humans, and that they use this to find food and see .

The blue reflection from the winter is likely to favour ultra-violet sensitivity.

Explore further: Deep sea fish eyesight similar to human vision

More information: "Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer" is published in Proceedings of the Royal Society B, can be viewed online at dx.doi.org/10.1098/rspb.2013.2451 from October 30. rspb.royalsocietypublishing.or… .1098/rspb.2013.2451

Related Stories

To Arctic animals, time of day really doesn't matter

Mar 11, 2010

In the far northern reaches of the Arctic, day versus night often doesn't mean a whole lot. During parts of the year, the sun does not set; at other times, it's just the opposite. A new study reported online ...

Recommended for you

Dogs hear our words and how we say them

Nov 26, 2014

When people hear another person talking to them, they respond not only to what is being said—those consonants and vowels strung together into words and sentences—but also to other features of that speech—the ...

Amazonian shrimps: An underwater world still unknown

Nov 26, 2014

A study reveals how little we know about the Amazonian diversity. Aiming to resolve a scientific debate about the validity of two species of freshwater shrimp described in the first half of the last century, ...

Factors that drive sexual traits

Nov 26, 2014

Many male animals have multiple displays and behaviours to attract females; and often the larger or greater the better.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.