The whale shark, recognized as the largest fish in the ocean, has a surprising diet. Despite its immense size, this gentle giant does not hunt large prey. Instead, it sustains itself on tiny plankton, using specialized methods.
The Primary Diet: Plankton
Whale sharks predominantly consume plankton. Plankton encompasses a diverse collection of organisms that drift through water bodies, carried by currents. This includes phytoplankton, which are microscopic plant-like organisms such as algae and diatoms, capable of photosynthesis. Zooplankton, the animal-like component, consists of tiny creatures like copepods, krill, and the larvae of various marine animals and fish eggs.
These small organisms provide the necessary nutrients for the whale shark’s substantial energy requirements. While individual plankters are minute, their sheer abundance in certain ocean areas allows whale sharks to gather sufficient sustenance. The reliance on these tiny food sources is an efficient adaptation for survival in diverse marine environments.
How Whale Sharks Feed
Whale sharks employ a highly specialized filter-feeding mechanism. They open their enormous mouths, which can stretch up to 1.5 meters wide, to take in vast quantities of water. This water, laden with plankton, then passes over unique structures within their mouths.
Behind their jaws, whale sharks possess specialized filter pads, which are modified gill rakers. These sieve-like structures, with openings averaging 1.0 to 1.2 millimeters in diameter, efficiently strain food particles from the water. The captured food is then swallowed, while the filtered water is expelled through their gills.
Two primary feeding techniques are ram feeding and suction feeding. Ram feeding involves the shark swimming forward with its mouth continuously open, pushing water and food inside. In contrast, suction feeding involves actively sucking in volumes of water, then closing its mouth to force the water out through its gills, retaining the food. Whale sharks have also been observed to “cough” to clear accumulated particles from their filter pads.
Beyond Plankton: Other Food Sources
While plankton constitutes the majority of their diet, whale sharks are not exclusively limited to these tiny organisms. They also consume other small nektonic life. This includes small fish, such as sardines, anchovies, and mackerel.
Their diet extends to small squid, jellyfish, and crab larvae. These larger, yet small, food items supplement their primary plankton intake. Consuming a variety of small marine life allows whale sharks to utilize available food sources across different oceanic conditions.