The hammerhead shark, instantly recognizable by its flattened, lateral head extension known as the cephalofoil, is a highly specialized predator that occupies a top position in marine food webs. This unique morphology is a sophisticated sensory tool that defines the shark’s hunting success in diverse ocean environments. The cephalofoil allows for a broad distribution of sensory organs and facilitates a distinctive hunting style unlike that of other shark species. The feeding ecology of the hammerhead family is varied, ranging from species that pursue large, swift prey to smaller species that graze on vegetation.
The Primary Prey of Large Hammerhead Species
The diet of the largest hammerhead species, such as the Great Hammerhead (Sphyrna mokarran) and the Scalloped Hammerhead (Sphyrna lewini), revolves heavily around other cartilaginous fish, particularly rays and skates. The Great Hammerhead demonstrates a pronounced preference for stingrays, a food source it pursues with specialized hunting tactics. Stomach content analyses confirm elasmobranchs are a primary dietary component.
The consumption of stingrays is a high-risk endeavor, evidenced by the discovery of dozens of venomous barbs embedded in the mouths and digestive tracts of some Great Hammerheads. These sharks also target a variety of bony fish, including grouper, sea bass, and sardines, hunting them in coastal and offshore waters. Cephalopods, such as squid and octopus, also form a significant part of the diet for these large species.
These apex predators are also known to consume smaller sharks, including conspecifics, demonstrating an opportunistic feeding strategy. Their diverse prey selection helps them adapt to the varying availability of food across their wide geographical range. The sheer size and power of the Great Hammerhead enable it to subdue prey that most other shark species would avoid.
How the Cephalofoil Assists in Hunting
The distinctive cephalofoil provides the hammerhead shark with a sensory advantage by maximizing the effectiveness of its electroreception system. The head extension spreads out the Ampullae of Lorenzini, the specialized pores that detect the faint electrical fields generated by living organisms. This wide distribution allows the shark to scan a much greater lateral area of the seafloor for hidden prey than sharks with conventional head shapes.
This enhanced electroreception is useful for locating stingrays and skates, which often bury themselves beneath the sand to camouflage. Studies suggest that the hammerhead can detect the minute electrical impulses of a buried ray, even when the prey is completely concealed from view. Once the prey is located, the shark employs a physical hunting technique involving the cephalofoil itself.
Observations show the hammerhead using its head to pin the ray against the substrate, effectively immobilizing the prey and preventing it from escaping or using its venomous barb defensively. In some instances, the shark has been seen using the edge of its cephalofoil to deliver a stunning blow to the ray. The wide-set eyes, positioned at the ends of the hammer, also contribute to the hunt by providing enhanced binocular vision and depth perception, allowing for precise tracking and attack once the prey bolts from the sand.
Specialized Diets and Omnivory Among Smaller Hammerheads
The feeding habits of smaller hammerhead species illustrate significant variation, highlighted by the omnivorous nature of the Bonnethead shark (Sphyrna tiburo). While most sharks are strict carnivores, the Bonnethead consumes a diet that includes a substantial amount of seagrass, which can constitute up to 62% of its gut content mass in some populations.
Scientific research confirms that the ingestion of seagrass is not incidental; the Bonnethead can digest and assimilate nutrients from the plant matter with an efficiency of approximately 50%. This capability is attributed to specific enzymes in its digestive system that break down the plant’s cell walls. The primary carnivorous portion of the Bonnethead’s diet consists of hard-shelled invertebrates, such as crabs, shrimp, and mollusks, which their flattened crushing teeth are well-suited to process.
Other smaller hammerhead species, like the Smooth Hammerhead (Sphyrna zygaena), focus on smaller prey items, including bony fish and cephalopods, but lack the omnivorous adaptation of the Bonnethead. The dietary diversity across the hammerhead family demonstrates evolutionary flexibility, allowing different species to exploit a wide range of available food sources in their respective coastal and pelagic habitats.