It is widely accepted that populations of large terrestrial animal predators (such as bears or tigers, for example) include “problem individuals” who repeatedly prey on humans. However, this phenomenon, which remained a mere hypothesis -published in 2018 in Conservation Letters (1)- had never before been demonstrated for aquatic predators such as sharks. In our latest study, also published in Conservation Letters (2), we describe three case studies from three different oceans (Pacific, Caribbean and Red Seas), involving two species dangerous to humans, the Tiger shark and the Oceanic whitetip shark, and using two different methods (photo-identification and genetic analysis), that a single shark killed a first person before going on to prey on other humans. These cases represent the first irrefutable proof that certain (rare) individuals among large sharks are capable of repeating attacks on humans. 

The percentage of these individuals is unknown, but this study calls for the systematization of DNA collection (by swabbing implemented by medical staff) on human victims of shark bites in order to better understand this phenomenon. This approach would enable the implementation of shark risk management strategies focusing on the strict elimination of animals for which there is evidence (via genetic matching) that they have already bitten and have a high probability – higher than their congeners – of attacking humans again (2). It also suggests outlawing the indiscriminate culling currently used by the authorities, which are not only ineffective but also environmentally deleterious and unethical, as they target animals that present no risk to humans.

Note: these recidivist sharks should not be equated with the concept of the “rogue shark” (“Jaws”). While they share this concept in that they repeatedly bite humans, they take no particular pleasure in doing so, and do not specialize in humans – two points which, until proven otherwise, are the stuff of science fiction.