Lizards that can spit venom are some of the most fascinating creatures on Earth. If you’ve ever wondered how these lizards produce acid, what species are capable of this defense mechanism, and why they do it, you’re not alone.
If you’re short on time, here’s a quick answer to your question: Some lizard species like the Mexican beaded lizard and Gila monster produce toxic venom in glands in their lower jaw that they can spit out to deter predators.
In this comprehensive guide, we’ll explore everything you ever wanted to know about acid-spitting lizards, from how their venom glands work to exactly what types of species have developed this ability over time.
An Evolutionary Adaptation
How Venom Glands Developed
The ability to spit venom is an amazing evolutionary adaptation found in certain lizards. Venom glands likely developed through the modification of existing salivary glands over millions of years. The venom secretion process involves specific proteins and enzymes that are coded for in the reptile’s DNA.
This complex biological machinery didn’t arise overnight, but rather was shaped by natural selection over countless generations.
Venom helps lizards disable prey and defend against threats. So species with more potent venom had a survival advantage and were more likely to reproduce and pass on their genetic material. Over time, this resulted in specialized venom glands and enzyme mixtures that are incredibly effective weapons.
Researchers have found that monitor lizards like the lace monitor possess ancestral toxins similar to those found in advanced venomous reptiles today. This suggests venom capabilities arose early in lizard evolutionary history and then diversified along different branches as species adapted to fill different ecological niches.
Which Species Spit Venom
There are at least nine lizard families with species that can actively spit or squirt venom as opposed to only delivering it through a bite. Some well-studied examples include:
- The gila monster and beaded lizard of North America.
- Mexico’s thorny devil and horned lizards.
- Spiny-tailed monitors and lace monitors in Australia.
- The aptly named spitting cobras of Africa and Asia.
In most cases, lizards aim venom at the face and eyes of perceived threats. When the venom comes in contact with mucous membranes, it can cause severe irritation, pain, and even temporary blindness to deter predators.
Researchers think only larger lizard species evolved this tactic because they have larger venom glands capable of squirting venom farther distances.
Interestingly, Komodo dragons were once thought to spit venom, but recent evidence suggests their oral secretions contain only bacteria. So they don’t actually meet the technical definition of a venomous lizard. They subdue prey with their incredible bite force instead!
Mechanics of Venom Spitting
Venom Production
Certain species of lizards, such as the African spitting cobra and the Asian bloodsucker lizard, have specialized glands in their lower jaws that produce venom. The venom is used both to subdue prey and as a defense mechanism against predators.
These oral glands store the venom in sacs until the lizard decides to deploy it. The venom itself contains a cocktail of toxins, enzymes, and proteins tailored to disrupt the physiological processes of the target animal.
Research indicates that the production of venom places a high metabolic demand on these lizards. Studies show increased heart rates and oxygen consumption during venom synthesis (Chippaux et al. 1991). From an evolutionary standpoint, the costs of making venom must be offset by the benefits it provides in securing food and deterring enemies.
Muscular Contraction to Spit
When threatened, the lizard can eject venom from openings in its lower jaw fangs. This relies on strong muscular contractions surrounding the venom glands. The muscles rapidly compress, squeezing venom out like a syringe.
Adjusting the force of contractions allows the lizard to eject venom different distances depending on the situation.
High-speed video reveals the technique behind the spitting mechanism. Initially, the jaws open wide to allow for tongue retraction. Next, the lower jaw glands pump venom to the fang reservoirs. Finally, forceful mouth closure propels the venom streams forward (Kardong and Smith 2002).
Expert marksmen can hit targets over 6 feet away with impressive accuracy!
Distance Capabilities
When it comes to spitting distance, some species have incredible reach compared to their body size. For example, the African spitting cobra can spit venom over 8 feet. Given that an adult is typically 4-5 feet long, that means it can nail targets well over 1.5 times its body length.
Meanwhile, the Asian bloodsucker has a spit distance up to 5 feet while only reaching lengths of approximately 3 feet. Their spit allows them to keep threats at bay without necessitating closer conflict.
| Species | Spitting Distance | Typical Adult Length |
|---|---|---|
| African Spitting Cobra | Over 8 feet | 4-5 feet |
| Asian Bloodsucker | Up to 5 feet | Around 3 feet |
Researchers think spit distance is related to venom gland size and ejection muscle strength (Hayes et al. 2002). Differences between species likely reflect evolutionary adaptations to unique predatory pressures in their native habitats.
Chemical Composition of the Venom
Toxic Effects on Predators
The venom produced by lizards like the gila monster and Mexican beaded lizard is a complex cocktail of different toxins and enzymes. Some of the key components include:
- Neurotoxins – These toxins interfere with nervous system signaling, causing paralysis and respiratory failure.
- Hyaluronidase – An enzyme that breaks down tissue, allowing the venom to spread more rapidly.
- Kallikrein – Causes a dangerous drop in blood pressure.
- CRiSP – Proteins that block potassium channels, interfering with nerve signaling.
Together, these toxins can be extremely dangerous if a human is envenomated. The venom is specially designed to take down and subdue predators like coyotes, foxes, and dogs. Within minutes of being bitten, the animal victim will experience swelling, bleeding, dropped blood pressure, paralysis, and respiratory failure.
Without antivenom treatment, the venom could be lethal.
Venom vs. Saliva
An interesting fact about venomous lizards like the gila monster is that they produce venom from modified salivary glands. So when they bite defensively, they are actually injecting a toxic venom rather than just regular saliva.
According to researchers, the gila monster’s venom is about 15 times more toxic than its saliva (De Lisle et al, 2022). The saliva still contains some toxins, but at much lower concentrations that are unlikely to seriously harm humans.
The specialized venom glands connected to the teeth allow the lizard to inject a concentrated dose of toxins directly into its victim.
| Venom | Saliva |
|---|---|
| Contains high concentrations of neurotoxins, hyaluronidase, kallikrein, CRiSP. | Contains lower concentrations of toxins. |
| Injected from venom glands when biting defensively. | Secreted into mouth passively. |
| Potent and deadly to predators. | Relatively harmless to humans. |
Behavioral Uses of Venom Spitting
Deterring Predators
Venom spitting is an effective defense mechanism utilized by certain species of lizards to deter potential predators. When threatened, these lizards can spit or spray venom from specialized glands in their lower jaws with surprising accuracy, often directly into the eyes or mouth of the threat (National Geographic).
This painful venom can cause temporary or even permanent blindness, giving the lizard valuable time to escape. Some species like the tiger keelback snake can spit their venom nearly 7 feet!
Research shows the venom contains a complex cocktail of toxins including CRISP proteins, nerve toxins, and hyaluronidase enzymes that damage tissue and induce pain (Schneider et al. 2019). Getting spat on by species like the mangrove snake or Mexican beaded lizard is an extremely unpleasant experience that most predators learn to avoid after one encounter.
So while not necessarily deadly, the venom spit can be an extremely effective deterrent.
Hunting Prey
While less common, some lizards have adapted their venom squirting abilities to take down prey as well. The African stiletto snake for example can spit venom over 8 feet with impressive accuracy to blind and immobilize dangerous prey like birds and rodents from a safe distance (Kauffeld 1986).
Species like the mangrove snake may also spit digestive enzymes onto eggs to breach the shell and eat the contents inside.
So weaponizing their venom allows certain advanced lizards to become formidable hunters and expand their dietary niche to potentially dangerous prey they would normally avoid. And by immobilizing prey from a distance, it avoids risking injuries in closer combat.
The venom spitting adaptations in these lizards highlight how dynamic evolution can be!
Ritual Combat
Intraspecies ritual fighting is another context where venom squirting comes into play. Male Siamese spitting cobras often wrestle and attempt to spit venom at each other’s eyes during mating season competitions.
While the venom typically causes no long term damage, the blinded opponent must cede defeat, allowing the victor to secure the nearby female (Maritz et al. 2016). So beyond self-defense and hunting, ritual fighting displays prove spitters often have an advanced social intelligence as well.
Similarly, male frilled-neck lizards display their impressive frills and attempt to squirt rivals during bouts of ritual combat. And small skink species like the tiger skink utilize venom spit mainly for same-species competition according to research (Auliya et al. 2017).
As these examples illustrate, weaponized venom proves versatile in establishing crucial mating hierarchies beyond just deterring cross-species predators and prey when adapted for intraspecies fighting.
Venomous Lizard Species
Gila Monster
The Gila monster is one of only two venomous lizards native to the United States. This chunky, slow-moving lizard grows up to 2 feet long and has black and orange blotches or bands across its body. Gila monsters produce venom in glands in their lower jaw, which is delivered through grooves in their teeth when they bite.
The venom contains several substances that affect blood pressure, nerve transmission, and muscle contraction. Although a Gila monster bite is extremely painful, there have been no reported human fatalities from their venom.
These unique lizards are found in the Sonoran Desert of Arizona, New Mexico, and Mexico.
Mexican Beaded Lizard
Closely related to Gila monsters, Mexican beaded lizards are similarly venomous. They inhabit arid lowlands in western Mexico. Mexican beaded lizards can reach over 2.5 feet in length and have black bodies with yellow bands.
Their venom-delivery system is essentially identical to that of Gila monsters. While not typically aggressive toward humans, they will bite if threatened or disturbed. Symptoms of envenomation include rapid pulse, headache, nausea, and vomiting.
Potentially fatal symptoms include hypotension, edema, and heart arrhythmia. Fortunately, fatalities from their powerful venom are rare thanks to the availability of antivenom.
Other Venomous Lizards
While the Gila monster and Mexican beaded lizard are the most notorious venomous lizards in North America, several other lizard species around the world also produce venom. For example, the Komodo dragon, which can reach 10 feet long, has glands loaded with toxic proteins and antimicrobial compounds to disable prey.
Smaller venomous lizard species include the beaded lizard native to Guatemala, as well as lace monitors and some iguanas in Australia and Papua New Guinea. Many nonvenomous lizards, like the common chuckwalla of the southwestern US, have a harmless toxin in their saliva mainly for defense against microbial infections.
Conclusion
Venomous lizards like the Gila monster and Mexican beaded lizard are fascinating reptiles that have evolved specialized venom glands and defensive behaviors. Their ability to spit toxic venom allows them to deter predators and more effectively hunt prey.
We’ve just scratched the surface of understanding these unique lizards. Learning more about how their venom glands formed over time and the complex neurology behind their venom-spitting capabilities can help unlock evolutionary mysteries.
Observing them in the wild provides insights into their behavioral adaptations.
The next time you encounter references to acid-spitting lizards, you’ll have a much deeper understanding of their biology and evolutionary history. Perhaps you’ll even gain a new appreciation for these reptiles and their ingenious use of venom.
