Some shark bites are ‘survival instinct', researchers say in defence of threatened predator

Euronews

26-04-2025

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'It's more scared of you than you are of it' is a refrain parents use to humanise spiders to their children. That's a little harder to believe of sharks, given their mighty appearance and characterisation in the media.
But researchers have found that - like snakes and spiders - sharks do sometimes bite humans in self-defence.
"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," says Dr Eric Clua, first author of the new
study
published in the Frontiers in Conservation Science journal.
"These bites are simply a manifestation of survival instinct, and the responsibility for the incident needs to be reversed,' according to Clua, a shark specialist and researcher at Université PSL in Paris.
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What makes a shark bite in self-defence?
Firstly, shark attacks are rare, occurring only 100 or so times a year. Just around 10 per cent are fatal;
statistically
, you are more likely to die in a lawn mower accident.
To understand more about shark bite motivations, which are already known to range from competition to predation, the researchers focused on the territorial waters of French Polynesia.
This 5.5 million square kilometre zone is home to more than 30 shark species, and has been a designated shark sanctuary since 2006, making it an ideal place to study shark behaviour.
The team used shark bite data collected systematically over the past 60 years in French Polynesia to identify self-defence bites on humans. They looked for incidents where sharks bit in response to aggressive human actions, such as spear fishing or attempts to grab the shark.
In contrast to 'feeding-motivated' bites,
sharks
acting in self-defence generally bite repeatedly and leave superficial, non-lethal wounds.
This lower-grade violence matches the kind of defence-motivated bites inflicted by land predators like bears and large birds such as cassowaries, the researchers note.
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How common are self-defence shark bites?
Between 2009 and 2023, 74 bites were documented in French Polynesia. Four of them were likely motivated by self-defence, the study found, which may trigger 3 to 5 per cent of all shark bites.
Collecting this data on a global scale is tricky, but the researchers made a start by applying their approach to the Global Shark Attack Files, which records almost 7,000 bites since 1863.
This database categorises bites as 'provoked' or 'unprovoked'. The researchers focused on the former, and bites linked to activities that might put people in proximity to sharks.
They found that 322 bite events could have been motivated by self-defence, a figure close to the percentage (around 5 per cent) of self-defence bites recorded in French Polynesia.
"We need to consider the not very intuitive idea that
sharks
are very cautious towards humans and are generally afraid of them," Clua says.
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When sharks strike in self-defence, they might use disproportionate force and deliver greater harm than is threatened (not unlike humans).
"The sharks' disproportionate reaction is probably the immediate mobilisation of their survival instinct,' adds Clua. 'It is highly improbable that they would integrate revenge into their behaviour and remain above all pragmatic about their survival."
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How can you avoid being bitten by a shark?
To avoid being bitten by a defensive shark, people should steer clear of any activity that could be considered aggressive, the researchers advise. This includes attempts to help stranded sharks, which are liable to be misinterpreted by the big fish.
"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," Clua cautions.
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"These are potentially dangerous
animals
, and not touching them is not only wise, but also a sign of the respect we owe them."
Knowing your coastal sharks is important, too. For some species, such as the territorial-minded gray reef shark, a human merely intruding into their space is likely to trigger their survival instinct.
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Reviewing our view of shark attacks
'The existence of self-defence bites … calls into question the practice of labelling all shark bites as attacks,' the researchers conclude.
The media plays a key role in this perception, tending to portray sharks as the aggressor even when people initiate the interaction. In April 2016, for example, reports on a bite incident involving two Polynesian fishermen who were aggressive a gray reef shark all had the word 'attack' in the headlines.
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'This simplistic approach damages the image of
sharks
and, indeed, their conservation, which relies on public support,' the researchers add.
With 'negative interactions' between humans and sharks on the rise due to our increased use of the sea, they hope their study will feed into a more sustainable style of wildlife management.
As in other areas of the animal kingdom, a better understanding of what motivates endangered species to attack people can help develop non-lethal strategies.