In a remarkable discovery, a whale shark has been observed engaging in a previously unseen feeding behavior at the seabed. As per the report of New Scientist, the whale shark was seen exhibiting a unique bottom-feeding behavior instead of its usual filter-feeding technique near the sea surface.
The behavior was caught in a video for the first time during a whale shark tour in Baja California Sur, Mexico. The footage, sent to researchers for analysis, shows a 5-meter-long juvenile whale shark actively sucking at the sand approximately 6 meters below the water's surface, seemingly consuming material from the substrate.
First Record of a Bottom-Feeding Whale Shark
Shark experts have made a groundbreaking discovery by capturing video evidence of a whale shark engaging in bottom feeding, a behavior never seen before.
Darren Whitehead of Investigación Tiburones México and Joel Gayford from Imperial College London received a GoPro video from a tourist who witnessed the event during a swimming tour near Baja California.
They analyzed the footage and published their findings in the study, titled "First record of bottom‐feeding behavior in the whale shark (Rhincodon typus)," in the Journal of Fish Biology.
Whale sharks, the largest fish in the world, typically inhabit warm tropical waters of the open ocean. They are known as omnivores, feeding mainly on fish and shrimp, but also consuming plankton such as krill, fish eggs, and copepods.
Until now, whale sharks were observed using two primary feeding methods: filter-feeding by swimming with their mouths open to capture small creatures and surface feeding where they actively pursue specific prey.
According to Phys.org, the newly documented behavior involves the shark descending to the seafloor and using suction to draw in material from the bottom. The shark in the video was filmed at a depth of just six meters, pushing its head down, sucking in food, and then expelling unwanted residue.
This suction technique closely resembles the behavior exhibited by whale sharks when feeding at the sea surface. The researchers believe the shark is targeting benthic creatures, particularly amphipods, which are small crustaceans living on the seafloor.
How Did the Whale Shark End Up Bottom Feeding?
Mark Meekan, a marine biologist from the University of Western Australia, told Live Science the recently observed bottom-feeding behavior in whale sharks was not entirely unexpected.
Meekan mentioned that, since the plankton consumed by whale sharks can migrate to the ocean bottom during the daytime, it is logical to assume that the sharks would also forage in that region. He further revealed that some of his students have recently captured footage of a whale shark engaging in similar feeding behavior.
Previous studies analyzing the dietary biochemistry of whale sharks had hinted at the possibility of them obtaining food from the ocean floor. However, no concrete evidence had been found until now. Gayford noted that this discovery might indicate that bottom-feeding by whale sharks is relatively rare in locations where interactions with humans usually occur.
It is plausible that these sharks predominantly engage in bottom-feeding activities far from the shore or at greater depths, he suggested. Gayford also proposed that such behavior might occur when their usual food sources are scarce, compelling the sharks to adopt alternative feeding methods.
Gayford highlighted the value of ecotourism in scientific discoveries like this one. He acknowledged the existing controversy surrounding shark tourism, especially when it involves shark feeding, but emphasized that tour guides who regularly encounter sharks have the potential to contribute significantly to scientific understanding.
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