Iguanas do not spit venom or saliva as a defensive or aggressive action. The behavior that looks like spitting is actually a forceful nasal expulsion, a necessary bodily function that has been widely misinterpreted. This action is a mechanism for maintaining their internal physiological balance.
The Truth About Iguana “Spitting”
The spectacle often mistaken for spitting is the iguana “sneezing” a clear, sometimes opaque, fluid out of its nostrils. This action is quick and forceful, which gives the impression of a deliberate projectile attack. The substance is not saliva or a toxic material, but a watery nasal discharge.
This forceful expulsion is often termed a “snot rocket” by observers due to its velocity. The spray is a highly concentrated solution of minerals that dries rapidly, frequently leaving a fine, white, powdery residue on the iguana’s face and head. This visual evidence confirms the mineral content of the expelled fluid.
The Physiological Reason for Salt Expulsion
The reason for the iguana’s nasal discharge lies in specialized organs called salt glands. These glands are located near the nasal passages and filter excess mineral salts from the bloodstream. Iguanas are primarily herbivorous, and the plant matter they consume can be naturally high in salts.
To maintain a healthy internal balance, or osmoregulation, the iguana must excrete these excess minerals. Unlike mammals, iguanas cannot rely solely on their kidneys, because filtering high concentrations of salt would require eliminating large amounts of water. Since water conservation is paramount for reptiles, the salt glands offer an efficient workaround. These glands collect the excess salts, concentrating them into a fluid that is then expelled through a powerful sneeze-like action. This allows the reptile to rid its body of excess minerals without suffering severe dehydration.
Other Common Iguana Defense Behaviors
While they do not spit, iguanas possess behaviors they use for threat display and self-defense. The most powerful defense mechanism is the tail whip. An iguana’s long, muscular tail can be swung with force to deter potential predators or rivals.
When an iguana feels threatened, it will engage in several visual displays to appear larger and more intimidating. This includes puffing up its body and rigidly extending the throat dewlap, the flap of skin hanging beneath the chin. They also perform head bobbing—a rapid, rhythmic movement—which is a common display for establishing dominance or issuing a warning. If cornered, an iguana may resort to hissing, scratching with its sharp claws, or biting as a last resort.