How Ultraviolet Light Reveals a Hidden World to Animals

An apparently ordinary flower may contain designs that no human can see with the naked eye. To a bee, however, these markings can act like genuine signposts. This is possible because many animals can detect ultraviolet light, part of the spectrum that surrounds us yet remains wholly invisible to human vision.

Why are humans unable to see ultraviolet light?

Human sight relies chiefly on three types of cone cells, each responsive to different areas of visible light. Structures such as the lens also block much of the ultraviolet radiation before it can reach the retina. As a result, wavelengths below violet do not register as a colour to us.

For many animals, the arrangement is different. Research into animal vision shows that certain species have ultraviolet-sensitive photoreceptors and eyes that allow this radiation to reach the retina. Studies of birds, for instance, have found visual pigments specialised for wavelengths of roughly 360 to 373 nanometres.

Which animals can see what humans cannot?

This ability occurs across very different animal groups. Bees, many birds, some fish, reptiles and even certain mammals can perceive at least part of ultraviolet radiation. Consequently, objects that appear to be one uniform colour to us may reveal entirely different contrasts and patterns to them.

• Bees detect ultraviolet light and use floral signals while searching for food.
• Many birds have colour vision based on four cone types rather than the three found in humans.
• Reindeer can perceive ultraviolet light even in the Arctic's extreme lighting conditions.
• Some lizards have eyes that permit ultraviolet wavelengths to pass through to the retina.

In birds, the contrast can be particularly striking. Scientific reviews describe many species as tetrachromatic, meaning they can combine information from four classes of cones. A bird's visual experience may therefore include colour distinctions with no direct equivalent in human perception.

How does ultraviolet vision help a bee find flowers?

Some flowers reflect ultraviolet light unevenly, creating patterns that may guide pollinators towards the areas containing nectar and pollen. Those markings are hidden from us. For a bee, they form part of the colours and contrasts used to identify and choose flowers while flying.

This does not mean that bees merely see a more colourful version of what we see. Their visual system differs from ours and lacks the same sensitivity to red. Nature therefore offers different visual maps for each species, shaped by the receptors in their eyes and by needs developed through evolution.

Watch the video shared by the INCREDIBLE YouTube channel, showing how the world is viewed through the eyes of other animals.

Can mammals see ultraviolet light too?

Although this ability is less widespread among mammals, reindeer provide a notable example. Research indicates that their eyes admit ultraviolet light, a trait that is especially useful in the Arctic, where snow reflects large amounts of this radiation at particular times of year.

Studies suggest that this form of vision may improve the contrast of important features in the environment. Lichens eaten by reindeer absorb ultraviolet light and may look darker against snow, making them easier to find. The same ability may also help them identify other objects that are difficult to distinguish in an almost entirely white landscape.

How much of the world around us remains unseen?

Ultraviolet light demonstrates that what we call visual reality is only a limited interpretation of our surroundings. Flowers, feathers and surfaces that look plain to our eyes may contain signals used for feeding, mate choice, communication or survival by species able to detect different wavelengths.

The more scientists examine these sensory systems, the clearer it becomes that we do not see the world as it truly is, but as our eyes are able to translate it. The next time you look at a flower or a bird, it is worth remembering that a complete layer of visual information may be unfolding in front of you without you being able to perceive even one of its colours.