UV light increases our risk of melanoma and cataracts.  This is especially harmful at higher lattitudes where both a thinning ozone layer lets even more UV light through and the snow and ice reflect UV light back up at us.

Reindeer are not only resistant to the harmful effects of UV light, but also are actually able to visualize it.  This allows them to identify their food (lichen) and predators (wolves), which would otherwise blend into the snowy landscape.

UV light is otherwise invisible to all but a few mammals, such as some species of rodents, bats and marsupials.

Read more here:  http://www.eurekalert.org/pub_releases/2011-05/babs-rsa051011.php