Sharks, a class of cartilaginous fish called Elasmobranchii, exhibit feeding habits that are far from routine, dictated instead by their species, size, and environment. Their diet is a specialized inventory of ocean life, and their feeding schedule is measured not in daily meals but in opportunistic, energy-intensive events. Understanding what sharks consume involves appreciating the vast evolutionary differences between the more than 500 species that inhabit the world’s oceans.
Diversity in Feeding Habits
There is no single answer to a shark’s diet, as their food ranges from microscopic plankton to large marine mammals. The most profound difference exists between the largest sharks, the planktivores, and the apex predators. Giant species like the Whale Shark, Basking Shark, and Megamouth Shark are filter feeders, consuming vast quantities of zooplankton and krill by sifting water through specialized gill rakers.
In contrast, most other sharks are carnivorous predators whose diets are specific to their hunting grounds and dentition. The Great White Shark exhibits a developmental shift in its diet; juveniles primarily feed on fish and rays, while adults target calorie-rich marine mammals such as seals and sea lions.
Other large predators display remarkable dietary flexibility. The Tiger Shark is an opportunistic feeder that consumes bony fish, seabirds, sea turtles, sea snakes, and carrion. Specialized hunters like the Hammerhead Shark prefer rays, utilizing their unique head shape and electroreception to pin and consume the prey. For the majority of smaller shark species, the diet is built upon a foundation of bony fishes, crustaceans, and cephalopods like squid and octopus.
Hunting and Consumption Strategies
The methods sharks use to secure their varied meals rely on an exceptional suite of senses. Long-distance detection is initiated by the shark’s highly developed sense of smell, which can detect minute concentrations of amino acids released by potential prey. This is paired with an acute sense of hearing, tuned to the low-frequency sounds associated with struggling fish from hundreds of meters away.
As a shark closes the distance, it engages its mechanosensory system, the lateral line, which detects vibrations and changes in water pressure. This system allows the shark to sense the precise movements of an animal in murky water or low-light conditions. At the final, immediate range, the shark relies on its electroreception, specifically the ampullae of Lorenzini. These jelly-filled pores detect the weak bioelectrical fields generated by muscle contractions, enabling a shark to locate prey buried under the sand or hidden within a crevice.
Consumption strategies vary widely based on the prey and the shark’s specialized teeth. Sharks that prey on small fish, like the Blacktip Shark, often employ a pursuit and ram-feeding strategy, rapidly overtaking their meal. In contrast, a Nurse Shark uses suction to pull stationary or benthic prey from the substrate. For large prey, the serrated, triangular teeth of a Great White Shark are designed for tearing and removing large chunks of blubber and muscle from marine mammals.
The Infrequent Feaster: Meal Frequency and Timing
Sharks do not adhere to a daily meal schedule like humans, making the concept of a routine “breakfast” entirely inaccurate. They are intermittent feeders, a pattern supported by the frequent observation of empty stomachs in wild specimens. This ability to go without food for extended periods is a direct result of their relatively slow metabolism as cold-blooded animals.
When a shark does consume a large meal, the energy required for digestion, known as Specific Dynamic Action, causes a significant and sustained increase in its metabolic rate. Studies on some shark species show that metabolic expenditure can more than double after feeding, with the entire digestive process lasting for many hours. A substantial meal can sustain a large shark for days, and in some cases, weeks, before it needs to hunt again.
Feeding is generally opportunistic, dictated by the availability of prey, but activity often peaks during periods of low light. Many species exhibit crepuscular feeding patterns, meaning they are most active and hunt most effectively around dawn and dusk. This timing is likely a behavioral adaptation that capitalizes on reduced visibility, allowing the shark to ambush or approach prey more effectively.