Snakes exhibit a remarkable ability to change their body shape by flattening. This temporary, voluntary action serves various purposes in their natural environment.
The Anatomy Behind Flattening
The unique skeletal and muscular structure of snakes allows for this dramatic change. Their numerous ribs, which can number from 175 to 400, are highly flexible and not connected by a sternum. Instead, these ribs are attached to a complex network of 10,000 to 15,000 muscles running along their spine and connecting to their skin.
When a snake flattens, it actively manipulates these ribs and the intercostal muscles between them. These muscles contract to push the ribs outward, expanding the body wall laterally while simultaneously flattening it dorsoventrally. This allows a snake to alter its cross-sectional profile.
Behavioral Reasons for Flattening
Snakes flatten their bodies for several reasons, primarily linked to survival. A common motivation is defense, where flattening makes the snake appear larger and more intimidating to potential predators. This bluffing tactic can deter threats without direct confrontation.
Thermoregulation is another function, as flattening increases the snake’s surface area exposed to sunlight. This allows them to absorb heat more efficiently from their environment, which is essential for ectothermic animals. Conversely, they may flatten to dissipate excess heat when temperatures are too high.
Beyond defense and temperature control, some snakes use flattening for locomotion, particularly arboreal species. “Flying” snakes, for example, flatten their ribs and undulate their bodies to generate lift, allowing them to glide between trees. Additionally, some species can flatten their bodies to squeeze through tight spaces, such as narrow crevices or under closed doors, to seek shelter or pursue prey.
Species That Flatten and Human Interaction
Many snake species exhibit flattening behavior. Hognose snakes are well-known for their defensive display, where they flatten their heads and necks, hiss loudly, and may even feign death if threatened. Cobras are famous for their hooding, expanding their neck ribs to create a wide, intimidating hood.
Other species, such as some rat snakes, brown snakes, and tiger snakes, also flatten their bodies or heads defensively. Arboreal snakes like vine snakes have naturally laterally compressed bodies, which can be further flattened for camouflage or when agitated. Eastern brown snakes, for instance, can flatten their bodies to squeeze through surprisingly small gaps, including under doors, to enter structures.
When a snake flattens, this behavior is almost always defensive, not aggressive towards humans. Snakes prefer to avoid confrontation and escape first. Flattening is a warning display. Giving the snake space and backing away slowly is the safest response, as striking is a last resort if escape is not possible.