The elusive yellow-scaled Gila Monster is one of the rarest of Southwest lizards and spends up to 90% of its mysterious life underground. Along with its cousin, the Mexican beaded lizard, it’s one of only two species of venomous lizards (out of a total of about 5,000) and is found throughout the Southwest United States including the Mojave, Sonoran, and Chihuahuan deserts.
Though Gila monsters can come in an array of different shades, their stocky bodies often appear in blotchy stripes of black and orange or yellow. Along with these stripes are thousands of tiny beaded scales that are so prevalent and dense they even show up on x-rays. Named after the Gila River in Arizona, these lizards live up to 20 years (30 years in captivity) and can grow to be up to 2 feet long. Their menacing appearance along with their foul breath are reasons why they were subjected to so many myths over the years by pioneers who often believed these reptiles were far more deadly and viscous than they actually are.
While not quite the monsters the pioneers believed them to be, Gila monsters are highly venomous and though they’re generally thought to avoid humans you might want to exercise some caution around these creatures. For one, you should always keep your distance around any desert dwellers to ensure that you don’t startle them and force them to experience any more stress than they are already under living in such harsh conditions. But secondly, a bite from one of these lizards, while likely not fatal, would still hurt like hades so you want to make sure not to get too close. You shouldn’t have to worry, though as almost every recorded bite from these animals came as the result of someone aggressively handling (or mishandling) these “monsters” and thus practically asking to get bit.
Unlike snakes, the Gila monster produces its venom in its lower jaw (as opposed the the upper jaw). Also, unlike snakes who inject their venom into their prey, the Gila monster inserts its venom through its teeth by chewing with its intensely strong jaw bones, often turning on its backside to increase the efficiency of secreting their venom. It’s said that they can hold on to their prey for up to 15 minutes, slowly secreting their venomous saliva into the wound as they dig their teeth deeper into the bite. The longer they hold on, the more venom enters the blood stream of their prey.
The use of this venom is thought to be mostly a defensive technique as evidenced by their hunting behavior. Gila monsters could easily use their potent venom to kill larger mammals, yet that’s not how they hunt. Instead, they rely mostly on bird and reptile eggs and newborn prey for their diet. They track down eggs by utilizing their exceptional sense of smell that’s so developed they can follow the trail of a rolling egg and locate it even when it’s buried up to 6 inches below the ground. This sense is attributed to the presence of the “Jacobson Organ,” an organ found inside the Gila monster’s mouth that collects the odor particles caught from the lizard’s tongue and sends messages to the brain of what kind of prey or predators may be nearby. This is the same organ found in many other reptiles, amphibians, and even is some mammals.
It’s rare for a Gila monster to feast more than ten times a year and some can go with as little as only three meals a year. However, when it is time to eat, these reptiles sometimes eat up to 1/3 of their total body mass to keep them nourished for as long as possible. When Gila monsters are unable to find prey, they depend on a storage of fat found in their thick tails for nourishment (they never give up their highly precious tails like other lizards). As their famine periods grow longer and they continue to rely on their fat deposits, it’s not uncommon for their thick tails to shrink down into a fraction of the size it once was.
While they are quite the predator, Gila monsters are also hunted by coyotes, raptors, and in their younger stages, even wild cats are known to attack them. One of the leading causes of death for Gila monsters (not surprisingly) is getting run over by automobiles, so try watch out for these little fellas if you’re driving through the Southwest. This sluggish movement of the Gila monster has earned it a reputation of being one of the more lethargic animals found in the Southwest. It’s true that Gila monsters aren’t going to be winning any sprinting medals against most other lizards but for what they lack in short-bursts of speed, these animals are amazingly well-adapted to endurance runs — scientists have shown that these reptiles can keep moving at steady paces for miles through the desert.
The best time to ever see a Gila monster would likely be early morning in the spring. This is the time of year when they actively hunt for food and also come out of their burrows to engage in their ritual battles with other Gila monsters for mates and territory. Despite having the capability of clawing each other up and injecting potent venom into each other, they engage in more of a wrestling match during these battles and choose not to fatally injure one another.
You may not ever catch one of these lizards moving around outside of the confines of a zoo or wildlife park but if even if you never see one, it’s hard not to appreciate these animals for their many resilient qualities and mysterious (and often unappreciated) beauty. Also, the Gila monster has given back to us humans in more ways than one. Scientists created a drug called “exenatide” by synthesizing a protein found in the Gila monster’s saliva and actually use this drug to help treat type II diabetes in humans. So while they may be menacing, it’s hard not like these “monsters” of the Southwest.