Ultraviolet Defense Mechanism

The human eye is an incredible creation. It not only allows us to sense the visual world around us, but its connection with the brain is amazing. The image that falls on the back of your eye is inverted, and your brain turns it over so that you see everything right side up. Most animals have eyes that do unique things, but not all of them use visible light. Ultraviolet light has a higher frequency than the light we can see. That means it is more energetic than the human eye can detect but less energetic than Xrays. Many animals use ultraviolet light as tools to enable them to survive. Some birds can see in the ultraviolet as do monitor lizards, some foxes, and some snakes. Sometimes ultraviolet vision helps them to find food. Other times prey use it as an ultraviolet defense mechanism.

Among the things those ultraviolet-seeing predators eat are lizards. A lizard called the blue-tongued skink lives on the ground throughout much of the continent of Australia. This lizard would seem to be an easy target for predatory birds and ground-dwelling animals. However, it has an ultraviolet defense. The tongue of the blue-tongued skink is highly efficient at reflecting ultraviolet light. When threatened by a predator, the lizard will open its mouth wide and stick out its tongue. The tongue will give off a blast of reflected ultraviolet light. Experiments show that birds and ground animals that see in the ultraviolet are startled by the sudden burst of ultraviolet radiation and veer away from the lizard.

One of the problematic things in designing any natural environment is building a system where living things can survive over the long term. If there is not a balance between predator and prey, the result is disastrous. Many years ago someone introduced rabbits to Australia. They had no natural enemies, and they reproduced so rapidly that soon the whole continent was overrun with them.

God has designed prey and predators in such a way that, if humans don’t mess it up, the environment and all of the living things in it can survive indefinitely. We are only now beginning to understand how difficult that is, even involving ultraviolet defense mechanisms. We need to allow the Earth to continue to be fruitful.
–John N. Clayton © 2018
Data from Behavioral Ecology and Sociobiology journal and reported on CNET.com