Animal-eye view of the world revealed with new visual software

August 6, 2015
Two Tenerife lizards (Gallotia galloti) are basking. The image on the left is in human-visible colours and although the male at the top is more colourful than the female at the bottom, he is still fairly well camouflaged amongst the foliage. However, the dusky blue/grey patches on his cheek and bars on his flank are much more conspicuous to the female lizard than ourselves, as highlighted in the false colour UV image on the right. This demonstrates how colours can be used as private signals in some species where evolutionary pressures for sexual signalling compete with evading predators. Credit: Jolyon Troscianko

New camera technology that reveals the world through the eyes of animals has been developed by University of Exeter researchers. The details are published today in the journal Methods in Ecology and Evolution.

The software, which converts digital photos to animal vision, can be used to analyse colours and patterns and is particularly useful for the study of animal and plant signalling, camouflage and animal predation, but could also prove useful for anyone wanting to measure colours accurately and objectively.

The software has already been used by the Sensory Ecology group in a wide range of studies, such as colour change in green shore crabs, tracking human female face colour changes through the ovulation cycle, and determining the aspects of camouflage that protect nightjar clutches from being spotted by potential predators.

Jolyon Troscianko from the Centre for Ecology and Conservation at the University of Exeter said: "Viewing the world through the eyes of another animal has now become much easier thanks to our new software.

"Digital cameras are powerful tools for measuring colours and patterns in nature but until now it has been surprisingly difficult to use to make accurate and reliable measurements of colour. Our software allows us to calibrate images and convert them to animal vision, so that we can measure how the scene might look to humans and non-humans alike.

Animal-eye view of the world revealed with new visual software
Dandelions as seen in human vision (left), and honeybee vision (right). The center of the flower absorbs UV while the ends of the petals reflects it. Credit: Jolyon Troscianko

"We hope that other scientists will use this open access software to help with their ."

Until now, there has been no user-friendly software programme that enables researchers to calibrate their images, incorporate multiple layers - visible and UV channels -, convert to animal colour spaces, and to measure images easily. Instead, researchers have needed to do much of this manually, including the sometimes complex programming and calculations involved. This freely available now offers a user-friendly solution.

Colour vision varies substantially across the animal kingdom, and can even vary within a given species. Most humans and old-world monkeys have eyes sensitive to three colours; red, green and blue, which is more than other mammals that are only sensitive to blue and yellow. It is impossible for humans to imagine seeing the world in more than three primary colours, but this is common in most birds, reptiles, amphibians and many insects that see in four or more. Many of them can also see into the ultraviolet range, a world completely invisible to us without the use of full spectrum cameras. So scientists studying these species need to measure UV to understand how these animals view the world.

Using a camera converted to full spectrum sensitivity, one photograph taken through a visible-pass filter can be combined by the software with a second taken through an ultraviolet-pass filter. The software can then generate functions to show the image through an animal's eyes.

Animal-eye view of the world revealed with new visual software
Echium angustifolium in Tenerife (Borage family). To us the flowers are a fairly uniform purple, but bees can see two UV absorbent patches at the top of the flower. Credit: Jolyon Troscianko

The researchers have provided specific data on camera settings for commonly studied animals, such as humans, blue tits, peafowl, honey bees, ferrets and some fish.

Flowers often look particularly striking in UV because they are signalling to attract pollinators that can see in UV, such as bees. UV is also often important for birds, reptiles and insects in their colourful sexual displays to attract mates.

The software is free to download and is available here.

Image Calibration and Analysis Toolbox - a free suite for measuring reflectance, colour, and pattern objectively and to animal vision by Jolyon Troscianko & Martin Stevens is published in Methods in Ecology & Evolution.

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4 comments

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zorro6204
2.3 / 5 (3) Aug 06, 2015
That's not really true, or at least we don't know how animals "see" the world. It's not like our eyes are camera lenses that display an image on a screen, our brains take the data received from the optic nerve and construct an image. A simple animal like a bee might not "see" a darn thing, the impulses from its eyes could simply be handled as data in its little computer. The way we see the world could be nearly unique, all the lower animals may be essentially blind, constructing no image of the world, experiencing vision like a bat does it's echo location function.
winthrom
5 / 5 (2) Aug 06, 2015
BTW. The link to the software is missing.
baudrunner
not rated yet Aug 06, 2015
All visual imagery is handled like"data". "Visible" electromagnetic waves that are communicated by the particles in the propagating medium - ie. the frequencies to which the cones and rods in the retina are tuned - are converted to bio-electrical signals which are conducted via the optic nerves to the occipital lobes so that the brain can construct imagery out of the information.

Birds have extra sets of color receptors, in addition to the ones that humans have, enabling them to supplement their vision by seeing into the UV range, and giving some the ability to perceive magnetic fields and polarized light.

I can't vouch for the accuracy of the reproductions in the article. The bird's image should be enhanced and amplified in some way, to the extent that the image should contain more information, be more vibrant.
qitana
5 / 5 (1) Aug 07, 2015
Well, if our eyes would take in the same combinations of frequencies of light, it still cannot be stated that we would see the same colours as the lizard would. Since light has no colours. Colours are constructed inside the mind. So it could even be true that, for example, that light with a frequency which we would perceive as yellow might be perceived as blue by the lizard. Since there is no absolute correspondence with the frequency of light and the colour that is perceived.

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