Cats and dogs have a 'sixth sense' - and it's UV vision

 Cats eyes: Scientists have said that cats and dogs can see in ultraviolet ¿ so they can see things that humans can't - but experts are not sure why the animals need the capability
Owners of curious pets might suspect that their animals have a sixth sense when they seem to be 'spooked' by nothing at all.


But now scientists might have gone some way to explaining their strange behaviour as they have said that cats and dogs have ultraviolet vision – so they can see things that humans can’t.
However, experts are not sure why the animals need the capability.

WHY MIGHT ANIMALS BE ABLE TO SEE UV LIGHT?

Scientists are not sure why some animals can see ultraviolet light and others can't.
It is thought that some use it to see in the dark as well as spotting potential mates or predators. Reindeer for example see UV light and it helps them spot polar bears that appear to be incredibly well camouflaged in white snow.
Bees and other insects use their UV vision to see colours and patterns on plants.
Rodents use it to follow trails of urine, but they are not sure what pets use it for.
Experts also question why human eyes filter out UV light.
Some think it could be to protect the delicate retina, but other animals that live for a long time and see UV do not have damaged eyes.
Other scientists consider that the human eye is best suited to seeing detailed images in low levels of light, whereas other creatures that see UV tend to see in less detail.

British researchers found that a whole plethora of mammals, including hedgehogs and ferrets can see in UV, giving them a better view at night among other benefits.
It was previously thought that only a handful of mammals could see ultraviolet light, but the new study could help scientists shed some light on why pets behave the way they do.
Ron Douglas, a biologist at City University London, in England told LiveScience: ‘Nobody ever thought these animals could see in ultraviolet, but in fact, they do.’

Light is made up of a spectrum of colours and humans can see from red to violet, whereas many animals, such as bees, fish, reptiles and amphibians can see ultraviolet wavelengths invisible to humans.
A number of mammals including bats, reindeer and some mice and moles are already known to see in ultraviolet, but scientists are not sure why some animals have it and others, as well as humans, do not.
The lens of the human eye blocks ultraviolet light, but in some animals UV can reach the retina and the light is converted into nerve signals, which travel to the brain and are processed.

Scientists thinks that the UV filter in the human eye means that we can see more accurately than without it. Humans can see in such detail because we have dense colour-sensitive cells (cones) in the retina (pictured) that convert light to create detailed images in dim conditions

To explore which animals possess the capability to see ultraviolet light, the researchers obtained eyes from a wide array of mammals that had died in zoos, vets, science labs or slaughterhouses.
They measured how much light got through each animal’s eye to the retina.
Scientists found that many of the animals, including cats, dogs, hedgehogs, ferrets and okapi, have lenses that let some ultraviolet light though, suggesting that they can see well in the dark.
Scientists already know that bees and other insects use their UV vision to see colours and patterns on plants, while rodents use it to follow trails of urine, but they are not sure what pets use it for.
‘The question is only being asked because humans can't see it,’ Dr Douglas said.

To explore which animals possess the capability to see ultraviolet light, the researchers obtained eyes from a wide array of mammals, including dogs and hedgehogs, that had died in zoos, vets, science labs or slaughterhouses

He is interested in why the human eye blocks UV light and while some scientists think it could be to protect the retina from damage, many animals that live for long periods of time and are active in the daytime, can see ultraviolet light and ‘their eyes don’t fall apart’.
Other scientists think that the UV filter in the human eye means that we can see more accurately than without it. They found that animals that also block this part of the spectrum have the highest resolution vision.
Humans can see in such detail because we have dense colour-sensitive cells (cones) in the retina that create detailed images in low levels of light, but nocturnal creatures have eyes that let in as much light a possible, including UV, but do not enjoy the same level of detail.

WHAT DO ANIMALS SEE?

Birds can see UV light, which means that the 'eye' markings in a peacock's tail features looks sharper

Scientists have long been fascinated by the colour vision of animals and what they see when they look at us.
A lot of animals, such as birds see ultraviolet so a peacock looking at a potential mate would not see the rainbow of colours like humans, but a plainer, yet vivid display of plumage.
Animal colouration provides some of the most striking examples of evolution by natural and sexual selection.
But animal colours did not evolve for our benefit; the impressive array of animal colours that we see (and can’t see) in the natural world allows animals to communicate with each other, to attract mates and to avoid predators.
Because animal colours evolved for the benefit of animal - and not human - eyes, understanding the visual world from an animal’s point of view can explain why some animals are bright while others are dull.
Some are highly patterned and others plain. This allows scientists not only to shed exciting new light on the animal colours we can see, but also to understand the importance of colours that they can’t.

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