While walking through the Wonderopolis desert, we witnessed a confrontation between a bobcat and a horned lizard:
Bobcat: Mr. Lizard, I am going to devour you now.
Lizard: Umm… I would prefer if you didn’t, if that’s okay.
Bobcat: Well, I am really famished and you look extremely appetizing, so…
Lizard: Actually, I do not taste anything like chicken, if that’s what you’ve heard.
Bobcat: Nevertheless, I believe you would make a splendid meal.
Lizard: If you take one step closer, I will expel blood from my eye into your face.
Bobcat: No way! Can you actually do that?
Lizard: Test me.
At that point, the bobcat walked away. This encounter made us wonder. Was the lizard simply bluffing?
As it turns out, the lizard was not bluffing. There are 17 species of horned lizards that inhabit dry, desert regions from Guatemala and Mexico to the western United States and even southern Canada.
They have various predators, including bobcats, wolves, coyotes, foxes, snakes, and hawks. Consequently, they have developed unique defense mechanisms.
Their primary defense mechanism is camouflage. Although the different species have different colors and numbers of horns, they typically blend in well with their desert surroundings. When predators approach, they usually remain motionless to avoid detection.
If they are detected, they may or may not attempt to escape. With their wide, flat bodies and short legs, they are not very fast. Some predators, like rattlesnakes, do not usually pursue their prey, so the lizards may flee from these predators.
Many predators can easily outrun and catch a horned lizard. When caught, horned lizards often stretch out and inflate themselves to appear larger. They do this to discourage predators who swallow their prey whole. If the predators cannot fit the entire lizard in their mouths, they may move on.
As a last resort, horned lizards may employ a final defense mechanism that is particularly effective against predators like bobcats, wolves, and coyotes. They expel blood from their eye sockets! This typically scares predators enough to make them retreat. Fortunately for humans, horned lizards rarely expel blood at people.
How do they do it? Horned lizards can contract the muscles around their eyes, restricting blood flow back to the heart. Blood continues to flow into the eye area, filling the ocular sinuses with blood.
They then rapidly contract the same muscles, increasing pressure on the delicate sinus membranes until they rupture, releasing a stream of blood that can travel up to four feet from the eye! Scientists refer to this process as auto-hemorrhaging.
If necessary, horned lizards can repeat this process multiple times within a short period. It also serves a practical purpose beyond defense. In their habitat, it is common for them to get dirt and dust in their eyes. They can carefully control the auto-hemorrhaging process to remove irritating particles from their eyes without fully rupturing their sinuses.
Try It Out
Are you ready to discover more about horned lizards? Make sure to engage in the following activities with a friend or family member:
- Watch National Geographic’s video of the Blood Squirting Lizard online to witness a horned lizard using its special defense mechanism against a coyote. How do you think the coyote reacts to being squirted with blood?
- Explore the Horned Lizard Conservation Society website to discover more about various species of horned lizards. You can also find photos of these different species. Which species do you believe have the most effective camouflage?
- Find out about other extraordinary ways animals defend themselves from predators by reading about Weird Animal Defense Mechanisms online.
Sources of Wonder
- https://asknature.org/strategy/eyes-squirt-blood/#.WZIaIVF96Uk
- http://www.bbc.com/earth/story/20151105-if-it-has-to-a-horned-lizard-can-shoot-blood-from-its-eyes
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