This Reptile Doesn’t Run Away, It Fights Back With Blood From Its Eyes

The Texas horned lizard lives in the arid environments of the southwestern region of America, and it has one of the most peculiar adaptive behaviors among all living organisms since it sprays blood from its eyes as a defensive mechanism, which sounds outrageous but is based on evolutionary adaptations.

Different from other animals that use mobility or concealment to protect themselves, this lizard uses a defense technique that looks bizarre yet works effectively in highly dangerous situations where attackers do not give up easily.

This phenomenon is called auto-hemorrhaging, in which the lizard can spurt its blood a few feet in the direction of the attacker.

How the blood-squirting mechanism works

The secretion of blood from the eye is not arbitrary; it follows a particular biological mechanism involving the regulation of blood circulation inside the animal's body.

This biological phenomenon is discussed on the website Enviroliteracy.org, wherein the lizard regulates blood flow exiting its head, resulting in a buildup of pressure in small blood vessels near the eyes until they rupture in a controlled way, thereby allowing the blood to flow out via the tear ducts.

Because of the regulation involved in the secretion of blood from the eyes, the secretion cannot be considered an involuntary action, but rather a specialized mechanism developed by some animals as a defense mechanism against recurrent attacks.

Moreover, the lizard can actually target its bloodstream at the face of the attacker, thus increasing the probability of interrupting the attack.

More than shock, the role of chemical defense

Although the mere appearance of blood can scare off any potential predators, there is much more to its defensive capability because the blood actually has chemicals within it that taste bad.

As reported on Science ABC, the awful taste might be caused by the diet of the lizard, as these reptiles consume venomous ants, and thus have accumulated some chemicals in their blood, making the latter unpleasant for some species of predators.

The technique works especially well against those animals that hunt using smell and taste, for example, coyotes and foxes. When coming into contact with the lizard’s blood, they tend to shake their head, thus giving the lizard the opportunity to flee.

According to research related to anti-predator adaptation, this experience is likely to result in a learned avoidance of similar prey.

Other defenses come first

As impressive as the act may be, it seems that the horned lizard does not depend on the use of its unique weapon as its primary defense mechanism, as it first tries to keep out of sight of any potential danger. It possesses spiny scales all over its body, and its skin color matches that of the desert surroundings, giving it ample opportunity to remain unnoticed by predators.

It is able to expand its body to give the impression of being bigger and less palatable, which further aids its defense mechanisms before having to use anything drastic.

As mentioned by the Arizona Sonoran Desert Museum, it seems to employ different levels of defense based on the threat level it perceives.

Not all species use this tactic

However, not all horned lizards use the blood squirting ability to protect themselves, indicating the presence of particular factors leading to the development of such an adaptation. For instance, the desert horned lizard mostly relies on its ability to remain unnoticed and to move swiftly, and does not engage in self-hemorrhaging.

The fact demonstrates that there is no one way to evolve, and depending on the predator and other factors, one adaptation may be better suited for the environment compared to another. Despite being a useful mechanism for protection, blood squirting can bring additional disadvantages as well.

A rare strategy in the animal world

Autohemorrhaging is rare among animals, but there have been instances reported in some other animal species as well, such as specific species of snakes. Researchers consider this auto-hemorrhaging as an instance of convergent evolution, where different species evolve similar features in response to similar environments.

It is a rare behavior and, therefore, makes the Texas horned lizard more intriguing to study.

What this reveals about survival

The ability of the Texas horned lizard to shoot its blood as a defensive mechanism provides an excellent illustration of how adaptation to difficult conditions may yield biological innovations that are hard to anticipate.

From the findings of several studies conducted on this topic, it is apparent that an efficient defense mechanism requires more than simply avoiding a predator. Instead, it involves altering the behavior of the predator in the long run.

Through the use of physiological characteristics, chemical deterrents, and learned behavior from the predators themselves, the Texas horned lizard has created a very unique form of defense.