Sharks often bite people in self-defense, not to attack

Sharks often carry a reputation as the ultimate beasts. However, shark bites remain rare. Only about 100 happen globally each year, and roughly 10% are fatal.

Sharks bite for many reasons. They might act out of competition, territorialism, or predation. Now, researchers have identified another reason: self-defense.

Dr. Eric Clua is a shark specialist and researcher at Université PSL and the first author of the study.

“We show that defensive bites by sharks on humans – a reaction to initial human aggression – are a reality and that the animal should not be considered responsible or at fault when they occur,” said Dr. Clua. “These bites are simply a manifestation of survival instinct, and the responsibility for the incident needs to be reversed.”

This discovery challenges common views. It suggests sharks often bite as an instinctive response, not as cold-blooded attackers.

Sharks bite because they feel threatened

Negative interactions between humans and sharks are not new. However, they have increased with more human activity at sea. Management now aims to minimize lethal responses to wildlife.

Sharks, much like land animals, react defensively when provoked. Yet self-defense motivations in sharks were rarely explored until recently. French Polynesia, with an exclusive economic zone that spans 5.5 million square kilometers, provided key insights.

Between 2009 and 2023, 74 shark bites were documented in French Polynesia. Four were strongly linked to self-defense. This proportion, about five percent, matches global trends when activities like spearfishing and fish trap use are considered.

Many shark bites happen without warning

Self-defense bites arise when sharks feel threatened by human actions. Activities like spearfishing or grabbing sharks often trigger these responses. Warning signs are rare or absent. Defensive bites usually cause superficial, non-lethal wounds.

This pattern is not unique to sharks. Bears and cassowaries also react similarly, defending themselves without a lethal intent.

“Some species of coastal shark, such as the gray reef shark, are both particularly territorial and bold enough to come to contact with humans,” said Dr. Clua. A human merely intruding their space could be enough.

Repeated bites during defensive events were noted, though fatalities remained rare. In many cases, minor to moderate injuries occurred, reinforcing the non-predatory nature of these incidents.

Sharks may react with strong defense

When sharks react in self-defense, the force may seem excessive compared to the human action.

“We need to consider the not very intuitive idea that sharks are very cautious towards humans and are generally afraid of them,” noted Dr. Clua.

“The sharks’ disproportionate reaction probably is the immediate mobilization of their survival instinct. It is highly improbable that they would integrate revenge into their behavior and remain above all pragmatic about their survival.”

This reaction closely mirrors human behavior under threat. Defenders often inflict greater harm than the attacker intends.

Additionally, there is no proportional link between human aggression and shark bite severity. Tooth anatomy and shark size primarily influence injury outcomes.

Case studies from French Polynesia

Detailed case studies shed light on real-world self-defense bites. One case involved two spearfishermen at Makemo Atoll in 2016. After injuring a gray reef shark, the animal retaliated, inflicting multiple non-lethal wounds.

Another case focused on traditional fish traps. Fishers entering traps to retrieve fish sometimes confronted trapped sharks. Attempts to spear sharks often triggered defensive bites.

A third case documented scientists trying to handle a blacktip reef shark for sampling. An improper grip allowed the shark to bite a scientist’s hand. These incidents illustrate that even non-aggressive handling attempts can trigger defensive behavior.

Self-defense bites are common

Globally, self-defense bites represent about 4.6% of all recorded shark bites, closely matching French Polynesian observations. Data from the Global Shark Attack Files supports this estimate.

For instance, Australian data shows that Wobbegong sharks often bite defensively when accidentally disturbed. This finding highlights that self-defense biting is not region-specific but widespread among various species.

The media often fails to differentiate these events, labeling them all as “attacks,” which harms shark conservation efforts.

Preventing shark bites

Avoiding aggressive or intrusive actions toward sharks is key to staying safe. Even well-meaning rescue attempts can be perceived as threats.

“Do not interact physically with a shark, even if it appears harmless or is in distress. It may at any moment consider this to be an aggression and react accordingly,” said Dr. Clua. “These are potentially dangerous animals, and not touching them is not only wise, but also a sign of the respect we owe them.”

Touching stranded sharks can lead to defensive bites. Their flexible bodies allow them to turn quickly and strike even when handled gently.

Sharks bite to survive

Recognizing self-defense as a motivation changes how shark incidents should be understood and managed. People must acknowledge their role in provoking many incidents.

This understanding can shift media narratives and reduce unjustified fears. Better reporting can also support shark conservation efforts, crucial for preserving ocean ecosystems.

Self-defense bites reveal sharks as cautious, pragmatic survivors rather than ruthless killers. Humans must revise their attitudes and actions when interacting with these animals.

Reducing aggressive encounters and respecting sharks’ space could lower incident rates. Meanwhile, more accurate media representation could significantly aid global shark conservation initiatives.

The study is published in the journal Frontiers in Conservation Science.

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