Whale sharks, the largest fish in the ocean, are gentle giants inhabiting tropical and warm temperate waters globally. They sustain their massive bodies by consuming microscopic plankton and small nektonic life. Unlike predatory sharks, whale sharks employ a specialized filter-feeding strategy. This allows them to process vast quantities of water, efficiently extracting sustenance to support their significant metabolic demands.
Understanding Their Daily Food Intake
Whale sharks consume substantial amounts of food each day to fuel their large bodies and support their migratory movements. A juvenile whale shark, around 6 meters (20 feet) in length, can consume approximately 21 kilograms (46 pounds) of plankton daily. A medium-sized whale shark of similar length has the capacity to filter over 600,000 liters of seawater in an hour. During concentrated feeding events, such as fish spawning, this shark might consume about 142.5 kilograms (314 pounds) of tuna eggs in a single day, equating to roughly 43,000 kilocalories.
Their diverse diet consists mainly of zooplankton like copepods, krill, shrimp, and crab larvae, as well as phytoplankton. They also feed on fish eggs, small schooling fish such as sardines, anchovies, and mackerels, and occasionally squid. These substantial energy requirements are met by ingesting large volumes of small prey, supporting their size and active lifestyle, including extensive migrations across oceans.
The Filter-Feeding Mechanism
Whale sharks employ an effective filter-feeding mechanism to capture their tiny prey. They possess a broad, flattened head with a mouth that can open to 1.5 meters (5 feet) wide. As the shark swims, water enters this large mouth, passing over specialized structures inside their pharyngeal cavity. These structures include over 300 rows of small, vestigial teeth that do not play a role in feeding.
Filtration occurs through a mesh-like tissue composed of 20 unique filter pads, which are modified gill rakers. These pads act as a sieve, trapping food particles larger than about 3 millimeters while allowing water to pass through and exit via the gill slits. Whale sharks utilize two main feeding techniques: ram filtration, where they swim forward with their mouth open, pushing water and food in, and active suction feeding, where they gulp volumes of water by opening and closing their mouth, even while stationary. Periodically, they may perform a “coughing” action to clear any build-up of particles from these filter pads.
Influences on Their Feeding Habits
Several factors influence a whale shark’s food intake. Prey availability is a significant determinant, with whale sharks often aggregating in areas experiencing seasonal plankton blooms or fish spawning events. These aggregations occur in specific regions like Ningaloo Reef in Australia and the Yucatan Peninsula in Mexico, where food sources are abundant. Their migratory patterns are closely linked to these food sources, as they traverse vast distances to find nutrient-rich waters.
The shark’s size and metabolic needs also influence its feeding behavior; larger individuals naturally require more sustenance. Water temperature plays a role, with whale sharks generally preferring warm waters and rarely found below 21°C (70°F). Environmental conditions, such as chlorophyll-a concentration (an indicator of phytoplankton biomass), can affect their feeding strategies, influencing whether they engage in passive ram feeding or more active suction feeding. Human activities, such as tourism provisioning, can also alter their natural feeding behaviors.