Dogs, cats and other animals may be able to see in ultraviolet, according to a study by researchers at City University London.

Light is made up of a spectrum of colours, with human vision spanning red to violet. 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.

Researchers analysed the eyes of 39 mammal species in order to determine how much light got through the lens of each animal’s eye to its retina. The researchers concluded that many of the animals, including dogs, cats and ferrets, have lenses that allow some ultraviolet light through, suggesting that they may see in ultraviolet.

Knowing that many animals have ultraviolet vision could provide a deeper understanding of why they behave the way they do. In short, they are seeing things that humans don’t see. Study leader, Ron Douglas, told Discovery News:

“There are many examples of things that reflect UV, which UV sensitive animals could see that humans can’t. Examples are patterns on flowers that indicate where nectar is, urine trails that lead to prey, and reindeer could see polar bears as snow reflects UV, but white fur does not.”