The biting mechanism of poisonous snakes involves four key phases:
- The Strike: The snake swiftly moves to bite its target.
- Opening of the Mouth and Elevation of the Fangs: The snake opens its mouth and raises its fangs for venom injection.
- Closure of the Jaws and Venom Injection: The jaws close, allowing the fangs to puncture the skin and inject venom.
- Retraction of the Fangs: After the bite, the fangs retract back into the snake’s mouth.
Each phase is carefully coordinated to ensure effective venom delivery, allowing the snake to subdue its prey or defend itself.
Snake Biting Mechanism
The snake biting mechanism is a highly specialized process that enables venomous snakes to deliver venom efficiently. It involves four key phases: the strike, fang elevation and venom injection, jaw closure with venom expulsion, and the retraction of the fangs. Each of these stages plays a crucial role in the snake’s ability to immobilize or kill prey, ensuring its survival. During the striking phase, the snake moves forward rapidly, followed by the opening of its mouth and elevation of the fangs to inject venom. After the venom is expelled, the fangs retract, preparing the snake for a potential follow-up strike. This intricate mechanism makes snakes some of the most effective predators in the animal kingdom.
Below is a detailed step-by-step breakdown of the snake biting mechanism:
1. The Strike
The strike is the initial phase where the snake propels itself forward with remarkable speed and force. Typically, the distance covered during a strike is about one-third of the snake’s length. Vipers are known for their rapid strikes, often faster than colubrids. Some species, particularly the hooded colubrids, compensate for their less mobile fangs by raising their heads, allowing for more effective striking.
2. Opening of the Mouth and Elevation of the Fangs
As the snake nears its target, it begins with closed jaws. The mouth opens swiftly as muscles such as the digastric, cervico-mandibular, and vertebro-mandibular contract, lowering the mandibles. Concurrently, the fangs elevate or rotate forward, facilitated by the pterygo-palatine-transverse arch, driven by the spheno- and parieto-pterygoid muscles. In colubrids, the fangs are grooved and generally shorter than those of vipers, with limited rotational capacity. The degree of fang elevation varies across species, ranging from 10° to 50°. The unique mechanism in colubrids involves the forward movement of the pterygo-palatine-transverse arch, leading to the projection of the fangs. This differs from vipers, where the maxilla’s movement on the prefrontal bone is a true rotary motion.
3. Closure of the Jaws and Injection of Venom
Once the fangs are embedded in the prey, the snake closes its jaws through the contraction of temporal muscles, elevating the mandibles forcefully. In colubrids, this contraction also compresses the venom gland, causing venom to be expelled through the fang’s duct. Interestingly, certain Australian species can expel venom even without making contact, during what is termed a “snap bite.” In vipers, the muscle arrangement around the venom gland allows for a more instantaneous and efficient expulsion of venom, independent of the jaw’s fixation.
4. Retraction of the Fangs
Following venom injection, the fangs are retracted through the contraction of retractor muscles that act on the pterygo-palatine-transverse arch. This action pulls the fangs downward and backward, ensuring they withdraw cleanly from the tissue. While these phases are described sequentially, in reality, they occur almost simultaneously, allowing snakes, particularly vipers, to deliver multiple lethal doses of venom within a fraction of a second.
Summary
This detailed examination of how poisonous snakes bite highlights the complexity and efficiency of the snake bite mechanism, particularly the process by which venom is injected. Each phase plays a critical role in ensuring that the snake can effectively neutralize its prey, illustrating the evolutionary adaptations that make snakes such effective predators.