Sharks and rays leap out of the water, or breach, for a wide variety of reasons, including courtship, birthing and hygiene, according to a review of scientific evidence, which finds that the behaviour is more common than previously thought.
Breaching has been reported among fast-swimming predatory sharks 鈥� such as white sharks (Carcharodon carcharias), shortfin makos (Isurus oxyrinchus) and salmon sharks (Lamna ditropis), as well as filter-feeding basking sharks (Cetorhinus maximus) and many species of ray, including manta, devil and eagle rays.
The animals use large amounts of energy to propel at least four-tenths of their body above the water 鈥� the researchers鈥� definition of breaching 鈥� so the behaviour must be beneficial.
Advertisement
鈥淎nyone who witnesses a breaching animal, be it a shark, ray or whale, should think of why they perform this acrobatic behaviour,鈥� says 聽at the University of California, Davis, one of the authors of the review.
These events are hard to study. 鈥淏reaches are rare and unpredictable, often occurring only once or a few times within a short period,鈥� says co-author at the Manta Trust, a UK charity. 鈥淭his makes gathering comprehensive data on the behaviour and its triggers quite challenging.鈥�
Studies have proposed a range of possible functions for breaching, based on direct observations, underwater and aerial photography and video, as well as data sensors attached to animals. The action could be a way of cleaning, dislodging external parasites, clearing gills, ejecting faeces or internal parasites, or to aid birthing, the researchers found. Breaching is also observed when a predator tries to chase, herd or stun its prey, as well as when animals try to avoid an obstacle, escape a threat, or attract or repel a member of their own species.
The analysis, the first to look at breaching across sharks and rays as a group, suggests there is no single reason for this highly specialised behaviour because each species鈥檚 lifestyle is so different. Klimley was surprised 鈥渢hat there are so many functions proposed for this behaviour,鈥� he says.
Breaches often take place during courtship rituals and researchers suggest the sound could be used for communication. 鈥淭he idea that sharks and rays might communicate with each other over long distances using splashes and breaches is particularly intriguing,鈥� says Stevens.
Environmental Biology of Fishes
