If you've ever wished you could see the world through the eyes of another animal, we have good news. As scientists specializing in color vision, we wondered about that and created a solution: a camera system and software package that allows us to record video in the colors of an animal's perspective.
Many animals can see ultraviolet light, including bees, birds, and even mammals such as reindeer and mice. In fact, the lack of UV sensitivity in humans is the exception rather than the rule. At the other end of the visible light spectrum, human eyes have receptors that are sensitive to red, but many animals, including bees, mice, and dogs, are blind to red as well as to ultraviolet light.
Even though blue and green are colors recognized throughout the animal kingdom, the exact wavelength of light that an animal perceives as “pure blue” or “pure green” varies by species. As a result, no species sees the world in the same color.
Take a look at the sky and understand that its blue color is a joint product of sunlight scattered in the atmosphere and your own sensory system. The colors you see are unique to you – in fact, for many animals, the sky is the color of ultraviolet light.
Then, slowly lower your eyes and try to imagine how the rest of the landscape would look to other species. Our new camera system brings us one step closer to understanding this wonderfully strange world inhabited by other animals.
Capture the world in motion
Although we cannot imagine what ultraviolet light looks like to animals that can detect it, we can visualize it using pseudocolor images. For example, bees that are sensitive to three types of light (ultraviolet, blue, and green) can shift their perceived colors into the human visible range, such that ultraviolet is blue, blue is green, green is red, and so on.
Until now, this process could only be applied to stationary objects. False color photography relies on taking a series of photos through a series of optical filters and then superimposing them. This sequential method means that everything must be in the exact same position in every photo.
Vasas et al. (2024) PLOS Biology
This is a significant drawback. This can be a laborious process that limits the number of objects that can realistically be imaged. For example, to take a photo of an iridescent peacock feather from 100 different angles, you would need to screw each filter on and off 100 times.
To make matters worse, all information related to the move will be discarded. However, the living world is always in motion. Trees sway in the wind, leaves flutter, birds hop along the branches, searching for insects in the undergrowth. I needed a way to visualize all this movement.
The first challenge was to devise a camera that records both ultraviolet and visible light simultaneously. The solution turned out to be a beam splitter. This special optical device reflects ultraviolet light like a mirror and transmits visible light like clear glass.
Vasas et al. (2024) PLOS Biology
We installed two cameras (the same kind you can buy in stores or online, nothing too fancy, but one modified to record in ultraviolet light) in a 3D printed case. The modified camera received the reflected UV light and the stock camera received the reflected UV light. Visible light transmitted. The recordings of these two cameras were overlaid and synchronized, and a series of transformation steps allowed us to calculate the amount of light that reached each camera's sensor.
From this, we can estimate the amount of light that would be captured by the animal's eyes if it were viewing the scene from the camera's perspective.
try it yourself
We have made all the code and camera system plans needed to implement the video conversion freely available online, and have made our best attempt to explain how to build a camera from scratch.
Our goal is for other researchers to build their own cameras and use them to answer their own questions about how other species see the world. There are many possibilities.
We can record the peacock's dance and see how dazzling the peacock's feathers look. The iridescence of these feathers extends into ultraviolet light. Our records show that the feathers appear even more colorful to our target audience than they do to us.
We can explain exactly what the caterpillar's startle display looks like to avian predators, and we can understand why the unexpected flash of colorful patterns scares the caterpillar away. You can ask questions about how animals move between locations on the forest floor to show or hide their colors.
We can also create image records of butterflies and other insects in museum collections and provide translations from an animal perspective as part of our digital library. It also allows the glass facade to be well visible to birds that might collide with it.
But the most interesting questions are the ones we haven't considered yet. It's only when we start capturing videos of the natural world in the colors animals see that we begin to realize how much information is out there. Discoveries await you in your own backyard.
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