Snakes often open their mouths remarkably wide. This action is a complex adaptation serving various biological functions. This specialized ability is important for their survival. It allows them to perform essential tasks like consuming prey, communicating, and maintaining bodily functions.
Eating and Swallowing
Snakes possess a unique jaw structure that enables them to swallow prey significantly larger than their heads. Unlike most animals with fused lower jaws, a snake’s lower jaw consists of two separate bones connected at the front by a highly elastic ligament. This allows the two halves of the jaw to spread apart laterally, dramatically increasing the mouth’s width. The upper jaw bones are also not rigidly connected to the skull, providing additional flexibility and rotational ability.
The jaw joint is positioned far back in the skull, contributing to the wide gape. When consuming a meal, snakes do not “unhinge” or “dislocate” their jaws; their skull bones are designed for extreme flexibility and expansion.
They employ a method known as “pterygoid walk” or “walk feeding,” where they alternately move the left and right sides of their jaws over the prey. Backward-pointing teeth help to grip the prey and prevent its escape as it is drawn into the throat. The skin of the lower jaw is extensible, with folds between scales that flatten out to accommodate large food items.
Threat and Defense Displays
Snakes frequently use wide mouth opening as a defensive strategy when they feel threatened. This gaping display serves as a clear warning to potential predators, aiming to deter them without physical contact. The open mouth can make the snake appear larger and more intimidating.
Often, this gaping is accompanied by other defensive behaviors, such as hissing. Hissing is produced by forcefully expelling air through the glottis, a small opening in the mouth, and the sound is amplified when the mouth is open. Some snakes may also perform bluff strikes with an open mouth, a warning action where they lunge without actually biting. This combination of visual and auditory signals is typically a last resort before a genuine strike.
Respiratory and Physiological Needs
Beyond feeding and defense, snakes open their mouths for various physiological reasons, often appearing like a yawn. This “yawning” behavior can help them readjust their jaws before or after consuming a large meal, ensuring proper alignment of the jaw bones. It also serves as a general stretch of the jaw muscles.
When swallowing large prey, a snake’s mouth and throat can become significantly obstructed, posing a challenge for breathing. To overcome this, snakes possess a specialized structure called the glottis, a tube-like extension of the windpipe located on the floor of their mouth. This glottis can be extended forward and to the side, acting like a snorkel, allowing the snake to continue breathing even while its mouth is full.
Snakes might gape to enhance their sense of smell, allowing more direct access for airborne chemical cues to reach their vomeronasal organ. While less common for wide gaping, snakes, being ectotherms, can also open their mouths slightly to aid in thermoregulation, particularly when attempting to cool down in very hot conditions.