Shark Attack Triggers Identified: Experts Reveal 'Dinner Bell' for Bull Sharks

Shark attack survivor Paul De Gelder, alongside predator specialist Rosie Moore, has identified key factors that can trigger bull sharks to attack humans. In a new Shark Week special, "Bull Shark Dinner Bell," the experts detailed how a combination of specific environmental conditions and human actions can act as a "dinner bell" for these aggressive predators.

Bull sharks are responsible for more shark attacks globally than tiger sharks and great white sharks, according to the Global Shark Attack File. De Gelder, who lost a hand and leg in a 2009 shark attack in Sydney Harbor, and Moore conducted experiments off Florida's coast to understand the triggers behind these incidents.

Factors Contributing to Attacks

Their research pinpointed three primary factors that create a "perfect storm" for bull shark encounters. The first is rainfall. Storms can agitate bull sharks, potentially due to the vibrations they create on the ocean's surface. Moore observed that sharks became more attracted and aggressive when water pumps simulated rainfall. "The rain has definitely triggered a more aggressive response. They're faster, bolder, more willing to bite," Moore stated. Sharks possess extraordinary sensory abilities, detecting tiny vibrations even in dark waters.

The second factor involves the presence of certain types of fish. Experiments involving different bait revealed that bull sharks were drawn to oily and fatty fish, such as bonito, rather than lean fish or even pork, which simulated human flesh. This preference suggests that the sharks' hunting patterns often overlap with the migration of these oily fish.

The third trigger relates to human activity. Bull sharks are highly sensitive to vibrations, and activities like spearfishing or diving can attract them. In one experiment, a bull shark attacked a spearfished fish, and other sharks moved into the area, exhibiting aggressive behavior. De Gelder simulated human splashing by jumping into the water, which immediately drew the sharks' attention. The sharks exhibited agitated behavior, with one biting De Gelder's scuba fin.

When these three elements—rainfall, fatty fish, and human activity—converge, the conditions become particularly dangerous. Moore described this convergence as a "perfect storm" where sharks exhibit heightened aggression and territorial behavior. "You can literally see how if all these elements lined up and you had somebody in the water that was not prepared, they would not stand a chance. The dinner bell has rung," she said.

Moore emphasized that while sharks generally avoid humans, bull sharks' behavior can be significantly altered by these combined factors. The researchers advise beachgoers to assess water conditions carefully before entering the ocean, noting that understanding these triggers could help prevent future attacks. In early July 2026, bull sharks were spotted off the New York coast, leading to swimming bans at local beaches.