Among the diverse shark family, the epaulette shark is a unique species inhabiting the shallow waters of the Western Pacific. It possesses a locomotion method that has gained attention for its ability to traverse not just the seafloor, but also exposed land. This behavior sets it apart from other sharks. This capacity for terrestrial movement hints at a suite of adaptations that allow it to thrive where others cannot.
Physical Characteristics and Habitat
The epaulette shark has a slender, elongated body, reaching lengths between 27 and 35 inches. Its most defining feature is a large, white-ringed black spot located just behind each pectoral fin, resembling the ornamental epaulettes on military uniforms. This distinctive marking gives the shark its common name. Its body is pale brown or beige, covered with darker brown spots and bands, and it possesses broad, paddle-shaped pectoral and pelvic fins.
These sharks inhabit shallow tropical waters on the coral reefs of Australia and New Guinea. Their preferred environments are reef flats and tidal pools, often in water barely deep enough to cover their bodies. The Great Barrier Reef, particularly the area around Heron Island, hosts a significant population of these sharks.
The “Walking” Shark Phenomenon
The epaulette sharkâs “walking” is a specialized form of locomotion. Instead of swimming, it presses its muscular, paddle-shaped pectoral and pelvic fins against the seafloor, wriggling its body to push and pull itself forward. This gait, which looks remarkably like a salamander’s, allows the shark to move through cracks and crevices in the coral reef inaccessible to other predators.
As the tide recedes, reef flats can become a network of isolated tidal pools. The epaulette shark uses its walking ability to move between these pools to hunt for trapped prey. This also serves as an escape mechanism, allowing the shark to move across exposed sections of the reef to reach the ocean or find more hospitable pools.
Surviving Extreme Conditions
The ability to walk across land is supported by an impressive physiological adaptation: a tolerance for hypoxia, or low oxygen levels. The shallow tide pools epaulette sharks frequent can become oxygen-depleted overnight as trapped organisms consume the available supply. Oxygen levels in these pools can drop by 80% or more.
The epaulette shark can slow its heart rate and breathing to cope with these conditions. It also manages blood flow, prioritizing the brain while reducing it to less critical parts of the body. This allows the shark to survive for hours in low-oxygen environments, enabling its foraging expeditions into isolated pools and brief journeys out of water.
Diet and Reproduction
The epaulette shark is an opportunistic predator feeding on bottom-dwelling invertebrates. Its diet primarily consists of polychaete worms, crabs, shrimp, and small bony fish that it uncovers in the sand and reef crevices. Younger sharks consume more worms, while adults prefer crabs and shrimp. Hunting is most active at dawn and dusk, using its sense of smell and electroreception to locate hidden prey.
Reproduction is oviparous, meaning the females lay eggs. The mating season runs from July through December, during which a female will deposit pairs of leathery egg cases, or “mermaid’s purses,” every couple of weeks. These cases have fibrous strands that attach them to the reef. This keeps them safe until the pups hatch after about 120 to 130 days.