Sharks, often seen as fearsome predators, exhibit diverse dietary habits. Their diets range from nearly microscopic plankton to substantial marine mammals, reflecting their adaptability across marine environments.
Diverse Diets Across Species
Shark diets depend on the species, their size, and available prey in their habitat. Many sharks are generalist predators, consuming various fish and smaller marine animals. For instance, bull sharks and tiger sharks are known for opportunistic feeding; tiger sharks are sometimes called the “rubbish bin of the sea” due to their flexible diet, which can include fish, seals, birds, and other sharks.
Other sharks are specialized hunters. Great white sharks, for example, are apex predators that primarily consume marine mammals like seals and sea lions, though fish and squid also make up part of their diet. Bottom-dwelling sharks such as nurse sharks and angel sharks forage on the seafloor, feeding on crustaceans like crabs and lobsters, as well as mollusks.
In contrast to active hunters, some of the largest shark species are filter feeders. Whale sharks, the largest fish in the world, and basking sharks consume plankton and small fish by filtering vast amounts of water. Basking sharks target zooplankton. A shark’s diet can also shift as it matures, with juveniles often starting with smaller prey and gradually moving to larger or different food sources as they grow.
Specialized Feeding Strategies
Sharks have anatomical and sensory adaptations to locate, capture, and consume prey. Their teeth and jaws vary greatly depending on their diet. Sharks that tear flesh, like the great white, have serrated, triangular teeth, while those that grip slippery fish may have pointed, needle-like teeth. Sharks that crush hard-shelled prey, such as crustaceans, often feature flattened teeth. Their jaw mechanics allow for strong biting forces.
Beyond dentition, sharks use sensory adaptations to find food. Their sense of smell can detect minute traces of blood or other substances, guiding them to potential meals. The lateral line system, a row of sensory pores along their body, detects subtle vibrations and pressure changes, indicating movement. Additionally, sharks possess electroreception through specialized organs called ampullae of Lorenzini, which detect the faint electrical fields generated by muscle contractions of living prey.
These adaptations facilitate various hunting techniques. Some sharks, like the great white, are ambush predators, launching surprise attacks. Others, such as mako sharks, are pursuit hunters, relying on speed to chase down fast-moving fish. Nurse sharks, with smaller mouths, utilize suction feeding, rapidly expanding their oral cavity to vacuum up prey from the seafloor or crevices.
Ecological Role of Shark Diets
Shark diets maintain the health, balance, and biodiversity of marine ecosystems. As apex predators or mesopredators, sharks exert top-down control on food webs. They regulate prey populations, preventing overgrazing or overpopulation that could destabilize the ecosystem. This maintains a natural balance and supports the health of other trophic levels, ensuring biodiversity and the flow of energy through the ecosystem.
Some shark species also act as scavengers, consuming dead or decaying organic matter. This scavenging behavior helps clean the ocean environment by removing carcasses and recycling nutrients.