Mudskippers (family Gobiidae) are amphibious fish known for their ability to thrive both in water and on the exposed mudflats and mangrove swamps of the Indo-Pacific region. These creatures spend a significant portion of their time out of the water, utilizing modified fins for terrestrial movement. Their unique habitat, which constantly shifts between wet and dry conditions, has driven the evolution of specialized locomotion strategies. How fast mudskippers can travel depends entirely on the mode of movement they employ and whether they are in water or on land.
Unique Methods of Movement
Mudskippers rely on distinct gaits to navigate the soft, uneven terrain of their intertidal homes. The primary form of sustained terrestrial movement is a slow, deliberate gait known as “crutching.” This involves the synchronous, alternating use of their highly modified pectoral fins, which function much like a pair of crutches. The fish vaults the anterior portion of its body over the planted fins, resting its weight temporarily on the pelvic fins before swinging the pectoral fins forward to begin the next stride.
This crutching motion allows for continuous, low-speed travel across the mudflat while keeping the body relatively straight. When a mudskipper needs a rapid burst of speed, typically to escape a predator or catch prey, it switches to a maneuver called “skipping” or “hopping.” Skipping is an escape response that involves quickly flexing the body and tail laterally, then rapidly straightening it to push off the substrate.
In aquatic environments, mudskippers primarily use axial undulation (body and tail movement) for fast swimming, similar to other fish. At slower aquatic speeds, they may use their pectoral fins in a paddling motion. They can also engage in a form of “water-hopping” or “hydroplaning” across the surface of shallow water, combining the burst power of their tail with a low-contact slide.
Quantifying Mudskipper Speeds
The speed of a mudskipper is highly variable and depends on the movement type, but crutching is a relatively slow gait. Sustained crutching speed has been measured in one study at approximately 4.47 centimeters per second (cm/s). This deliberate, low-speed movement is characterized by the body often coming to a complete stop between each stride, highlighting that stability and control take precedence over velocity.
When threatened, the mudskipper’s burst speed is dramatically faster, relying on the skipping or leaping motion. This explosive maneuver allows them to cover significant distance in a single bound. Mudskippers can leap distances of up to 61 centimeters from a stationary position. Males also use this powerful jump, sometimes reaching heights of up to two feet, for courtship displays.
The substrate also influences the speed and efficiency of crutching. Studies have shown that mudskippers adjust their gait, sometimes incorporating tail use, to improve their displacement per stride when moving over soft, deformable mud or inclined surfaces. When moving on dry sand or inclined terrain, they may use their caudal fin as a secondary propulsor, effectively doubling the distance covered in a single stride cycle.
Physical Features Enabling Terrestrial Movement
The ability of mudskippers to move on land is due to specialized anatomical adaptations not seen in fully aquatic fish. Their pectoral fins are the most notable feature, featuring elongated, robust skeletal elements known as radials. These radials create an “intra-fin” joint that functions analogously to an elbow, allowing the fin to bend and articulate when pushing off the ground.
The robust nature of the fins is further supported by thickened fin rays and a reinforced shoulder girdle, which provides strength for bearing the fish’s body weight against gravity. The pelvic fins are also adapted for terrestrial support. In some species, the pelvic fins are partially or fully fused, forming a suction cup-like disc that provides grip and support on soft mud or when climbing vertical surfaces like mangrove roots.
The tail, or caudal fin, is a functional appendage for terrestrial locomotion. It has short, stiff ventral rays that are used to anchor the body during the burst-skipping motion. To sustain activity out of water, mudskippers possess an extensive network of capillaries beneath their skin, allowing them to absorb oxygen directly from the air, provided their skin remains moist.