Researchers reveal that thresher sharks use tail-slaps to hunt
Scientists have shown that thresher sharks hunt schooling fish by bullwhipping their tails hard enough to maim and kill several prey at once, according to research published in the open access journal PLOS ONE by Dr Simon Oliver, Dr John Turner and Tim D’Urban Jackson from Bangor University’s School of Ocean Sciences, and Klemens Gann and Medel Silvosa of the Thresher Shark Research and Conservation Project in the Philippines.
The paper ‘Thresher sharks use tail-slaps as a hunting strategy’, describes the first observations of thresher sharks hunting in the wild. Thresher sharks are oceanic and pelagic and much of the knowledge of them to date is based on fisheries bycatch. The study shows that thresher sharks initiate explosive shockwaves in the water column, which are lethal to schooling prey fish, by whipping their tails in a trebuchet catapult-like motion. The results provide an insight into the behavioural ecology and biology of a shark species, which urgently requires protection.
Dr Simon Oliver, founder of the Thresher Shark Research and Conservation Project and now at Liverpool University, undertook the research while at the School of Ocean Sciences, Bangor funded by a NERC Studentship supervised by Dr John Turner.
He said “This extraordinary story highlights the diversity of shark hunting strategies in an ocean where top predators are forced to adapt to the complex evasion behaviours of their ever declining prey. The study profiles new knowledge on sharks interacting with and adapting to their natural environment, and provides an informed basis for conservation management to protect these sites, which form part of their habitat.”
The paper published in PLoS One, an Open Access journal, has generated significant interest, the story having been picked up by the BBC, Nature, Science, National Geographic, Plant Earth, and the Guardian within hours of publication.
Dr John Turner said 'people are fascinated by the lives of animals that they rarely see and these sharks usually live out in the oceans where they are rarely encountered by people. The large tails of these sharks have been the subject of much speculation, and our observations in the wild show the spectacular manoeuvre in which the tail is used to stun prey. Our earlier research showed that they ventured inshore onto coral reefs on sea mounts to be cleaned by parasites, and we highlighted our concerns over their vulnerability close to shore. By finding out more by their ecology and behaviour, we can better find ways of protecting them. Simon's work has already has great impact in the Philippines, and demonstrates what can be achieved with motivation, careful observation, and underwater technology'.
The researchers tracked shark activity with handheld video cameras and analysed 25 instances of tail-slapping to stun prey. Sharks appeared to initiate the behavior by drawing their pectoral fins inward to lift their posteriors rapidly, followed by tail-slapping forceful enough to stun or kill several prey, and cause dissolved gases to bubble out of the water. After a successful tail-slap, thresher sharks ate up to seven fish at a time.
Dr Oliver said “Hunting strategies employed by sharks are diverse and vary among species and individuals.”
For large marine predators, being able to stun more than one prey at a time is likely to be a more efficient means to hunt than chasing after many small fish in a school. Dolphins and killer whales are known to use tail-slaps to control or stun prey, while humpback and sperm whales use tail-slaps to communicate at the surface over long distances.
“It has long been suspected that thresher sharks use their scythe-like tails to hunt, but the behaviour, which is unique to their taxa in the animal kingdom, has been poorly understood.” said Dr Oliver. “The evidence is now clear; thresher sharks really do hunt with their tails.”
The research was funded by the UK’s Natural Environment Research Council, the paper and supporting video footage can be downloaded online from http://dx.plos.org/10.1371/journal.pone.0067380
Publication date: 12 July 2013