The great hammerhead shark is an imposing marine predator. Its distinctive shape and considerable size prompt questions about its interactions with humans. Understanding this creature involves exploring its natural history and behavior.
Great Hammerhead Profile
The great hammerhead shark (Sphyrna mokarran) is the largest hammerhead species, distinguished by its hammer-shaped head, or cephalofoil. This cephalofoil is wide with a nearly straight front margin, and its eyes and nostrils are positioned at the ends of its lobes. Great hammerheads typically reach 12 to 18 feet (3.6 to 5.5 meters) in length, with some recorded up to 20 feet (6.1 meters) and weights approaching 991 pounds (449.5 kg).
These sharks inhabit warm temperate and tropical waters globally, frequenting coastal areas, continental shelves, and lagoons, and are highly migratory. They are apex predators with a diverse diet, primarily consuming stingrays, rays, and skates. Their hunting strategy often involves using their cephalofoil to pin down stingrays on the seabed, then biting off pieces. Their diet also includes bony fish like groupers and sea catfish, as well as other sharks, squid, and crustaceans.
Human Encounters and Attack Data
Great hammerhead sharks exhibit a wary disposition toward humans, making unprovoked attacks extremely rare. The International Shark Attack File (ISAF) is a comprehensive database that tracks shark incidents worldwide. According to ISAF, hammerhead sharks, including great hammerheads, have been involved in a limited number of unprovoked attacks.
Since 1580, only 18 documented unprovoked attacks have been attributed to hammerhead sharks within the genus Sphyrna, with no recorded human fatalities. This low number is notable considering the many human activities in their habitats. While their size makes them potentially dangerous, their behavior often involves curiosity rather than aggression toward divers. The species is not considered a significant threat to swimmers, and most encounters are non-aggressive.
Circumstances of Rare Incidents
For the rare instances where great hammerheads show aggressive behavior toward humans, specific circumstances often play a role. Spearfishing is one activity that can sometimes lead to an interaction. The presence of struggling fish, or blood from a catch, can attract sharks and potentially lead them to view the spearfisher as a competitor for food.
In such situations, a shark’s natural predatory instincts might be triggered by commotion and scent, rather than an intent to prey on humans. The shark might also approach out of curiosity, investigating the source of the activity. While these interactions are infrequent, they underscore the importance of understanding and respecting the marine environment and its inhabitants. Aggressive encounters with great hammerheads are exceptional events, often linked to specific stimuli in the water.