It brings new meaning to the phrase ‘shark att.ack’.
While most people will be familiar with images of seals being vi.ole.ntly sm.ashed out of the water snatched in the jaws of a shark, it appears some are exacting their re.ve.nge on the ocean pr.edators.
Scientists have reported multiple cases of cape fur seals at.t.ac.king blue sharks off the coast of South Africa.
Scientists have reported multiple cases of cape fur seals at.ta.cking blue sharks and e.at.ing their g.uts off the coast of South Africa. Diver Chris Fallows captured this image. The behaviour has left marine biologists baffled as to why the seals have turned to at.ta.cking the torpedo-shaped sharks
The seals, which are normally p.re.y for great white sharks, have been seen at.t.a.cking and k.i.ll.ing medium-sized blue sharks, devouring their g.uts before leaving the rest of the ca.rc.ass.
Divers also report seeing the fur seals a.t.tac.king other species of shark and rays.
The behaviour has left marine biologists baffled as to why the seals, which normally h.unt smaller fish, have turned to a.t.t.ac.king the torpedo-shaped sharks.
The blue sharks are around the same size as the seals and it is thought to be the first time a seal has been seen p.re.ying on such a large p.reda.tor.
It was first observed by marine photographer Chris Fallows, who runs a dive boat operation from Cape Town in South Africa.
Dr Neil Hammerschlaf, a marine biologist at the Rosenstiel School of Marine and Astmospheric Science who was involved in the study, said the seals appear to be e.a.ting the g.u.ts of the sharks as they contain the most energy.
The blue sharks are around the same size as the seals and it is thought to be the first time a seal has been seen pr.eying on such a large pre.dator. An expert said there are relatively few reports of pinnipeds, or seals, preying on sharks in general, and in all cases these involved smaller sharks
Blue sharks, like the one above, are one of the ocean’s top predators with a sleek body and mouth full of teeth. Dr Neil Hammerschlaf, a marine biologist at the Rosenstiel School of Marine and Astmospheric Science said the seals appear to be e.ating the g.uts of these sharks as they contain the most energy
He said this behaviour may have serious implications for blue sharks, as their numbers are already in decline due to over fishing.
‘Seals are generally considered p.rey of larger sharks,and blue sharks have been observed pursuing juvenile and adult male Cape fur seals, though no k.il.ls have been witnessed,’ he continued.
‘There are relatively few reports of pinnipeds (seals) preying on sharks in general and in all cases these involved smaller sharks.
Cape fur seals, like the one pictured, normally use their manoeuverability to prey upon smaller fish and squid. Scientists believe that the seals could also be a.t.tac.king the sharks partly to remove competition for the fish they normally eat
‘The consumption of large sharks by a Cape fur seal is a departure from the prevalent view of this species’ diet, which is generally reported to consist of a diverse diet of small fish species, cephalopods and birds.
‘The prevalence of the behaviour reported here is unknown – it could reflect opportunistic predation by a generalist predator or it might be a common tactic.
‘These observations are important not just for understanding the interactions between these two species but more broadly for their implications in understanding the trophic ecology of pinnipeds – many populations of which have increased while numerous shark populations have declined.’
Fur seals have been known to mob great white sharks in large numbers but this is thought to be a defensive tactic to s.ca.re them away from breeding col.on.ies.
In this case the fur seals have been observed at.ta.cking the blue sharks, which are open ocean predators that can grow to be about 9ft long (2.82 metres), on their own.
Mr Fallows, who runs Apex Expeditions, first noticed the behaviour in 2004 while on a dive off Cape Town.
Fur seals are common p.rey for great white sharks, which snatch them in their jaws from below (above). Fur seals will often group together and mob these sharks, but this is thought to be a defensive tactic
In 2012 he again saw a large Cape fur seal a.t.t.ack five blue sharks from a shoal of ten over a two hour period.
The sharks were estimated to measure between 3.6ft (1.1 metres) and 4.5ft (1.4 metres) in length.
Mr Fallows said: ‘They swim up to them and grab them. There is no protracted chase.
‘It is almost as though the sharks are not expecting this to happen and do not overreact to the seal’s advances.
‘We have seen them feeding on three other small species of sharks. We have also observed them feeding on rays.
‘I would think it is possibly a learned behaviour based on limited normal food availability.’
A study on the behaviour is now published in the African Journal of Marine Science.
Scientists believe the seals could be a.tt.a.cking the sharks partly to remove competition for the fish they normally eat.
Dominic Tollit, a marine mammal consultant with the Sea Mammal Research Unit in Canada, told New Scientist that at.tac.king such a large and heavily armed pre.dator is a high-risk strategy if simply looking for food.
He said: ‘Would you at.ta.ck a lion if you’re hungry, or would you go for something smaller?’