What triggers a shark feeding frenzy?

It begins subtly, with one person spotting the box of doughnuts in the break room. What a stroke of luck to find this treasure hours before lunch! Maybe she'll share the news with a colleague across the cubicle, and soon enough, others will take notice. People might see their co-workers heading toward the break room, doughnuts in hand. Perhaps the irresistible scent of sweet glaze fills the air. Before long, it's a full-blown sugar-fueled chaos as office workers scramble for the last doughnut. There's no time for pleasantries. It's all about doughnuts now. A feeding frenzy ensues.

From wolves to birds to turtles, animals have been known to go wild over food and fiercely compete for it. The term 'feeding frenzy' has been used to describe everything from brides hunting for the perfect wedding dress to journalists clamoring for a juicy, scandalous story. But the term itself was first popularized by sharks in V.M. Coppleson's 1958 book 'Shark Attack.' It’s that depiction that truly captures the wild, uncontrollable nature of a feeding frenzy [source: Safire].

A shark feeding frenzy occurs when multiple sharks battle for the same prey. Sharks are typically solitary feeders, and a feeding frenzy reveals why. To an onlooker, it may appear as though the sharks have lost all control, attacking anything in their path with an uncontrollable fury. Their bodies thrash, their snouts lift, and their backs arch—clear signs of an impending assault. Some reports even mention sharks attacking one another or continuing to feed even after they've been fatally wounded by other sharks [sources: Encyclopedia Britannica, Martin].

But what triggers these feeding frenzies? Some studies suggest that sharks are always driven by hunger, regardless of how full they are [source: Parker]. Does this mean a feeding frenzy could happen at any time? What makes them become so frantic? And why can't they just share? We’ll delve deeper into the causes of feeding frenzies on the next page.

Shark Feeding Frenzy Causes

Certain scientists have noted that feeding frenzies can occur in nature, particularly in shallow waters where seabirds, seals, and sea lions gather. However, such events don't seem to happen often in the wild. Instead, feeding frenzies are likely rare occurrences triggered by a 'supernormal stimulus,' such as high stress levels in the water [source: Parker].

Research has revealed that sharks can detect distressed prey; they respond to the scent of injured fish and can hear the sounds of a struggling person in the water [source: Shark Trust]. Given the option, sharks will always choose injured prey, as it requires less energy to capture. The situation becomes chaotic when multiple sharks arrive to take advantage of the prey's vulnerability.

It's worth mentioning that many species maintain a sense of structure even during a frenzy. For instance, the Caribbean reef shark continues to follow a sort of hierarchy during a feeding frenzy [source: Dehart]. The whitetip reef shark also exhibits (somewhat) organized behavior amidst what appears to be a violent feeding frenzy. If the feeding frenzy attracts several sharks, they may unintentionally bite each other in the chaos [source: Dehart].

Many feeding frenzies begin near fishing boats, especially when fishermen pull in a net full of fish. The fish thrash in the net, possibly injured during their capture, and the chemicals they release attract sharks. The scent of blood excites the sharks, making them think they’ve discovered an easy meal, but when more than one shark appears, the situation becomes competitive.

In the event of a shipwreck, sharks may be drawn to the panicked humans splashing around in the water. During World Wars I and II, it was believed that the oceanic whitetip shark caused numerous feeding frenzies when boats were torpedoed and planes shot down. This deep-water shark often arrived first at maritime disasters, like the World War II sinking of the Nova Scotia steamship. Of the 1,000 men aboard, only 192 survived, with many fatalities attributed to whitetip feeding frenzies [source: Bester].

Humans are not typically on a shark's diet. Shark attacks on humans are usually a mistake or a test bite to determine the taste. However, one activity that may be contributing to more feeding frenzies is Shark feeding dives, where divers in cages descend into the depths to get close to sharks. To attract sharks, diving companies use chum, a mixture of blood and fish remains. Nowadays, feeding frenzies are most commonly observed when sharks are lured with artificial bait [source: Parker].

In 1975, the U.S. National Park Service warned people not to feed wild animals in national parks and reserves, as providing supplemental food alters their feeding behaviors. If sharks begin to associate humans with food, they may seek out humans who aren't offering anything. Several swimmers have already been injured in areas previously frequented by divers [source: Alevizon]. Moreover, many argue that artificial feeding undermines the purpose of observing these creatures in their natural environment.

Whether it's the frantic movements of prey or a turbulent mixture of blood and remains, the extreme stress generated by these elements appears to trigger sharks, pushing them into a frenzy. As more sharks are drawn to the scene, the chaos escalates, with the splashing intensifying. Scientists have yet to determine how much of a feeding frenzy is driven by hunger and how much is about asserting dominance in a way that seems chaotic to us. Nonetheless, feeding frenzies are another aspect that makes sharks both terrifying and captivating.