The axolotl, often called the Mexican walking fish, is a unique amphibian that retains its larval characteristics throughout its adult life, a phenomenon known as neoteny. Unlike most salamanders, the axolotl remains fully aquatic, navigating its freshwater environment in the lakes and canals near Mexico City. This permanent aquatic lifestyle necessitates specialized movements for both rapid transit and slow, deliberate exploration of the lake bed. The creature’s movement is a fascinating blend of fish-like propulsion and the early tetrapod crawl.
Primary Movement: Swimming and Tail Propulsion
The axolotl’s primary method for quick or sustained travel is swimming, which heavily relies on its muscular, flattened tail. This locomotion is characterized by lateral undulation, where the body and tail move in a side-to-side, wave-like motion. The style is similar to the anguilliform movement seen in eels and some fish. Propulsive force is generated as this wave of curvature travels down the body, pushing against the water.
The speed of swimming is directly correlated with the frequency of the tail beat; the faster the tail whips back and forth, the quicker the axolotl moves. Although they possess four limbs, these appendages are generally held close to the body and contribute little to forward thrust during active swimming. The limbs are occasionally used for slight adjustments in direction or body orientation.
Axolotls are hydrostatic swimmers, meaning they can control their position in the water column. Their swimming style is less hydrodynamically efficient than that of many true fish. This reduced efficiency favors maneuverability and fast escape bursts over long-distance cruising, suiting their natural, bottom-dwelling habitat. Their powerful tail allows for quick bursts of speed, particularly when lunging for prey or evading a threat.
Movement on Substrate: Walking and Crawling
When the axolotl is not swimming rapidly, it uses a slow, deliberate crawl to move across the lake or aquarium bottom. This low-energy behavior is used for exploratory movements or short-distance repositioning. The small, somewhat delicate limbs, which remain underdeveloped due to neoteny, are utilized in this process.
The four limbs coordinate in a slow, alternating pattern to push the body forward along the substrate, differentiating this action from tail-driven locomotion. This crawl allows the animal to maintain close contact with the bottom, which is important for a species that hunts primarily by ambush. The front limbs primarily support the head and chest, while the hind limbs provide additional push.
This slow, four-limbed movement gives the axolotl its common nickname, the “Mexican walking fish.” They often prefer a fine sand substrate to crawl on, as it provides better grip than a bare surface. The crawling motion is essential for navigating the complex terrain of their environment without expending the energy required for sustained swimming.
Posture and Sedentary Behavior
The axolotl is naturally an ambush predator and spends a significant portion of its life in a largely sedentary state, conserving energy while waiting for prey. Their typical “movement” is often limited to minor adjustments in posture or position rather than active travel. This stillness is a defining characteristic of their behavior in both the wild and captivity.
When resting, an axolotl typically sits on the substrate with its limbs spread out. They can maintain varied and sometimes awkward-looking resting positions for extended periods. This sedentary behavior is a normal, energy-saving posture for a creature that relies on surprising its food.
The axolotl can also manipulate its buoyancy to maintain a position in the water column just above the substrate, a form of hovering. They achieve this by making slight adjustments to the amount of air in their lungs. They may take a gulp of air at the surface to increase buoyancy, or release gas to sink. This allows them to drift subtly or remain suspended without continuous swimming effort.