Texas horned lizard

Creature Feature: Lizards Under Pressure

By Jen Schill and Jeanette Lim from the Biomimcry Institute

A lizard covered in horns and spines might not sound appetizing to us, but to many other animals, it’s a tasty treat!

Horned lizards, also known as horny toads because of their toad-like round body and blunt snout, live in deserts and semi-arid regions from southern Canada to Guatemala.

Texas horned lizard
This Texas horned lizard was observed in Arizona. Photo by Ginger Allington (CC BY-NC-3.0). Submitted to the Great Nature Project.

To fend off predators including hawks, snakes, wolves, and coyotes, horned lizards use several lines of defense. First, their bodies are covered in spiny armor. Some species can even inflate into what looks a bit like a spiny balloon. That doesn’t sound tasty! But some species, including the Texas horned lizard, coast horned lizard, and regal horned lizard, excel in using an even stranger defense strategy: shooting blood from their eyes.

How does a lizard do this?

It constricts muscles near its eyes to reduce blood flow out of its head, which builds up blood pressure. Talk about hot-headed! The rapidly increasing blood pressure in the thin-walled sinuses within the lizard’s eye sockets eventually breaks the sinus walls. When these walls break, blood shoots out of the eye in jet-like squirts that can travel up to four or five feet! The lizard can repeat this process several times in a row. Think your seasonal allergies are bad? At least your sinus pressure doesn’t do this!

Evidence suggests that, by shifting its eye muscles, the lizard can even control the direction of the squirt, helping to aim at its target. Not only that, but scientists think that a chemical in its blood is noxious to canids (such as dogs, coyotes, and wolves). It’s no wonder that startled predators often give up on making the lizard lunch and run the other way.

Believe it or not, the lizard is thought to use a similar blood pressure-building strategy to remove dirt and other unwanted material from its eyes.

What can humans learn from this resourceful strategy?

How might we apply the horned lizard’s bizarre strategy to solving human challenges? Perhaps we could apply it in fields such as agriculture, medicine, or mechanical engineering. For example, maybe the lizard’s control of its blood pressure could inform designs for control valves or more efficient hydraulic systems for storing, transporting, and distributing fluids.

In recent years, horned lizard populations have been on the decline due to habitat destruction, eradication of ants (their main food source), and the pet trade. Think of the inspiration we’d lose for making human designs more sustainable if we don’t protect this and other species.

Have you ever looked to nature for inspiration to solve a problem? You can see more examples of how to learn from nature by browsing the AskNature collection of Great Nature Project photos.

The Great Nature Project

Submit your photos of horned lizards or any other living thing to the Great Nature Project. You can keep track of your observations and get help from other people to identify what you saw. Browse or search the photo stream to see other amazing living things. Create an account to your share your photos of plants and animals.

More to learn and do

Interested in classroom activities related to biomimicry? Find free resources on the Biomimicry Institute’s Biomimicry Education Network.

To learn more about the horned lizard’s bizarre defense strategy and how we might apply it to make our human world more sustainable, check out AskNature.

Interested in contributing to AskNature? Learn more about sharing graphics, interning, and more.

Jen Schill is the Biomimicry Institute’s AskNature content manager and gets to explore cool biology and nature-inspired innovation ideas every day. She can’t cross a stream without picking up rocks to see what’s underneath. Jeanette Lim is the AskNature content coordinator and gets to talk about nature’s wonders and inspiration with other nature lovers. Her favorite animal is the hagfish.

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