Studies have shown that animals like cats and dogs can see UV light, which means that their vision can detect things that humans can’t see. This has led many to speculate that these animals can see a wide range of frequencies that are undetectable to the human eye. If you believe in ghosts, these findings may even lead to wonder if your pet can see souls that are on another plane of existence.
Ronald Douglas, a professor of biology at City University London and Glenn Jeffrey, a professor of neuroscience at University College London, conducted a study about ultraviolet vision in the animal kingdom the animals and published their findings in the Proceedings of the Royal Society B.
“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,” Ronald Douglas, co-author of the study, told Discovery News.
Many other animals, like fish and birds, were known to see these different wavelengths of light. However, this study was the first to show that this ability exists in cats, dogs, hedgehogs, ferrets, bats and several other rodents. This vision may also explain how animals are able to mark their territory with urine, or see in the dark.
“Nobody ever thought these animals could see in ultraviolet, but in fact, they do,” Douglas said.
According to Discovery News, “Man-made optical brighteners are sometimes added to paper, fabrics, laundry detergents, cosmetics and shampoos to make them appear brighter. Since optical brighteners absorb light in the UV spectrum, they might appear different, or stand out more, to UV-sensitive animals.”
Insects and bugs like bees can also see ultraviolet light, which helps them detect pollen in flowers, as the image below shows:
Seeing how easier it is to detect pollen, it can be assumed that this type of vision would make mammals far better hunters. However, it is actually rare for mammals to be able to see the UV part of the spectrum.
The image of the bunny below shows how UV sensory detection could make it easier to detect prey that has evolved to blend in with its environment.
“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,” Glen Jeffery said.
According to the abstract of the study:
Although ultraviolet (UV) sensitivity is widespread among animals it is considered rare in mammals, being restricted to the few species that have a visual pigment maximally sensitive below 400 nm. However, even animals without such a pigment will be UV-sensitive if they have ocular media that transmit these wavelengths, as all visual pigments absorb significant amounts of UV if the energy level is sufficient. Although it is known that lenses of diurnal sciurid rodents, tree shrews and primates prevent UV from reaching the retina, the degree of UV transmission by ocular media of most other mammals without a visual pigment with in the UV is unknown. We examined lenses of 38 mammalian species from 25 families in nine orders and observed large diversity in the degree of short-wavelength transmission. All species whose lenses removed short wavelengths had retinae specialized for high spatial resolution and relatively high cone numbers, suggesting that UV removal is primarily linked to increased acuity. Other mammals, however, such as hedgehogs, dogs, cats, ferrets and okapis had lenses transmitting significant amounts of UVA (315–400 nm), suggesting that they will be UV-sensitive even without a specific UV visual pigment.
In addition to body heat and urine, these animals can also other things that are invisible to humans, such as various chemicals, even the very mild chemicals that are used to brighten paper. Animals have many senses and advantages in the world that humans are just barely learning to understand. These findings could help us understand more about our reality, or perhaps help us create technology that allows us to heighten some of our senses to the level of these animals.