Reindeers need ultraviolet light

Reindeers need ultraviolet light

THE UNIVERSITY OF WESTERN AUSTRALIA

"This adaptation in reindeer allowed them to find food and escape predators in light conditions that would challenge other mammals." Image:moori/iStockphoto The unexpected finding that Arctic reindeer avoid the damaging effects of ultra violet light that causes snow blindness in humans by allowing UV light to pass into the eye, contrasts with most other mammals including humans where UV light is prevented from entering the eye by the cornea and lens. Winthrop Professor David Hunt, a member of The University of Western Australia's Neuroecology Group in the School of Animal Biology, said this adaptation in reindeer allowed them to find food and escape predators in light conditions that would challenge other mammals. Professor Hunt is co-author with colleagues from institutions including University College London, the University of Tromsø in Norway and Moorfields Eye Hospital in London, of a paper published in the Journal of Experimental Biology today in which it is suggested that UV vision is vital to the reindeer's survival. For the reindeer, it means that vision is extended into the UV spectrum, which is important since many objects that absorb UV have high contrast against the highly reflective snow surface.  So the reindeer with its specially adapted eye can see a main source of food - lichen - as well as its main predator, the wolf with its white fur that also absorbs strongly in the UV and therefore appears dark to the reindeer against the white snow. "What remains uncertain however is how the retina in the reindeer is protected against the damaging effects of the UV light that penetrates the eye". Professor Hunt is a highly cited expert with more than 200 publications about vision which include studies in humans and other primates, birds, marsupials and fish. UV sensitivity is rare among placental mammals although more common in marsupials, and is certainly absent in humans but was known from Professor Hunt's previous research to be present in parrots: the budgerigar and African grey.  In other recent work published inProceedings of the Royal Society, Professor Hunt studied representatives from all the long-lived parrots - South American macaws, Caribbean amazons, Indonesian and Australian cockatoos, the Australian rosella and the New Zealand kea - in all, a total of 14 species.  In every case, the findings indicated that UV-sensitivity was present. "We humans wear sunglasses to protect our eyes from UV rays but this is not a luxury that is available to a reindeer or a parrot," Professor Hunt said."  The ability to see into the UV means that the world is coloured differently to a reindeer or a parrot.  For the parrot, it may be useful for foraging for food or for selecting a mate.  A parrot's feathers strongly reflect UV light so what looks dull to us may look very bright and enticing to a mate." The reindeer research was funded by Britain's Biotechnology and Biological Sciences Research Council.