A reindeer, a cat and a dog could therefore probably see a white-furred animal, such as a bunny, hopping through a snow blizzard, while most people would just see a blur of all white.
Douglas, a professor of biology at City University London specializing in the visual system, and co-author Glen Jeffery, a professor of neuroscience at University College London, determined that cats, dogs, rodents, hedgehogs, bats, ferrets and okapis all detect substantial levels of UV.
"It has been known for nearly a hundred years that many invertebrates, such as bees, see UV," Douglas said, adding that birds, fish, and some reptiles and amphibians were added to the list in more recent decades.
"However," he added, "it was assumed that most mammals do not see UV because they have no visual pigment maximally sensitive in the UV and (instead possess) lenses like those of man, that prevent UV reaching the retina."
He explained that visual pigments are the substances that absorb light and turn it into the electrical activity that nerve cells transmit. They turn out not to be always necessary for UV sensitivity. Instead, the "ocular media" (transparent parts of the eye like the cornea and crystalline lens) in certain animals transmits UV wavelengths.