The Texas horned lizard, Phrynosoma cornutum, is a reptile known for its flattened, wide body covered in spiny protrusions and prominent horns on its head. These lizards exhibit earthy colors such as browns, tans, and grays, allowing them to blend into their surroundings. Found across arid plains, grasslands, and deserts from Texas to northern Mexico, this species employs specialized behaviors to avoid predation and ensure survival.
Blending into the Environment
The Texas horned lizard’s initial and most frequent defense relies on its ability to blend seamlessly with its environment. Its natural coloration, varying from yellowish tints in sandy areas to reddish or dark brown in other soils, closely matches the ground where it lives. This cryptic coloration allows the lizard to disappear against bare soil, rocks, and sparse vegetation. The flattened body shape casts only a slight shadow, helping to break up the lizard’s outline.
When a potential predator approaches, the lizard often employs a freezing behavior, remaining motionless to avoid detection. This stillness, combined with its natural camouflage, makes it exceptionally difficult for predators to spot. This passive strategy is highly effective, allowing the lizard to escape notice without engaging in more energy-intensive or risky behaviors.
Physical Displays of Defense
When camouflage and immobility prove insufficient, the Texas horned lizard can resort to active physical displays to deter threats. The prominent horns on its head can be strategically oriented to present a formidable barrier to an attacker. The lizard may also flatten its torso and lower its tail, facing the threat with an open mouth in a defensive posture.
A striking behavior involves rapid body inflation, where the lizard quickly takes in air, causing its body to puff up. This inflation makes the lizard appear significantly larger and more cumbersome, making it difficult for a predator to swallow or grasp. If the threat persists, the lizard may hiss and lunge as a further deterrent. These visual and behavioral displays combine to create an imposing appearance, often enough to persuade a predator to seek easier prey.
The Unique Blood-Squirting Defense
The Texas horned lizard is most renowned for its unique defense of squirting blood from its eyes, a process known as autohaemorrhaging. This behavior is executed by constricting muscles around blood vessels in the sinuses located behind its eyes. This constriction rapidly increases blood pressure in the head, causing the tiny blood vessels around the eyes to rupture and eject a stream of blood.
The lizard can aim this stream with accuracy, often targeting the mouth and eyes of an attacker, and it can reach distances of up to 5 feet. The effectiveness of this defense stems from noxious chemicals present in the blood, which are particularly unpalatable or irritating to certain predators, especially canids like coyotes, foxes, and domestic dogs. Some research suggests these defensive compounds may be sequestered from the harvester ants that form a significant portion of the lizard’s diet. This extreme response is typically a last resort, deployed when other defenses have failed and only against specific types of predators.
Quick Burial Tactics
Another distinct behavioral defense employed by the Texas horned lizard is its ability to rapidly bury itself in loose soil or sand. The lizard uses its specialized body shape and movements, wiggling and pushing itself beneath the surface, to quickly disappear from sight. This quick burial serves as an effective escape behavior, creating a physical barrier between the lizard and its predator.
This tactic is particularly useful in its preferred habitats, which often feature sandy or loamy soils. Beyond immediate predator evasion, burying itself also serves other purposes for the lizard, such as thermoregulation during hot afternoons and providing shelter for hibernation during cooler months. The ability to vanish underground rapidly aids the lizard’s survival in its often harsh environment.