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Color My World: Cats and Dogs May See in Ultraviolet

A house cat's bizarre antics may be more than just feline folly. The kitty may be seeing things that human eyes can't.

Unlike humans, many animals see in ultraviolet, and a study now suggests that cats, dogs and other mammals can, too. Knowing these animals see things invisible to humans could shed some light on the animals' behavior, the researchers say.

"Nobody ever thought these animals could see in ultraviolet, but in fact, they do," said study leader Ron Douglas, a biologist at City University London, in England.

Light is made up of a spectrum of colors. Visible light (that humans can see) spans from red to violet, and beyond the visible lie ultraviolet wavelengths. Many animals are known to have UV-vision, including insects (such as bees), birds, fish, some amphibians and reptiles, and a handful of mammals (such as some mice, rats, moles, marsupials and bats). [Images: See the World Through Cats' Eyes]

The lens of the human eye blocks ultraviolet light, but in animals with UV-transparent lenses, ultraviolet light reaches the retina, which converts the light into nerve signals that travel to the brain where the visual system perceives them.

Even in animals whose retinas aren't very sensitive to UV light, some of the light is still absorbed. (In fact, humans who have had their eye lenses removed, such as in cataract surgery, without being replaced by ultraviolet-blocking lenses report being able to see in the ultraviolet.)

In this study, the researchers obtained eyes from a smorgasbord of mammals — everything from hedgehogs to red pandas to macaque monkeys — who had died or were killed, donated by zoos, veterinarians, slaughterhouses and science labs. The scientists measured how much light got through the lens of each animal's eye to its retina.

The team found that many of the animals, including hedgehogs, dogs, cats, ferrets and okapis (relatives of giraffes that live in the central African rainforest), have lenses that allow some ultraviolet light through, suggesting these animals may see in the ultraviolet.

This is a condensed version of a report from Live Science. Read the full report.

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