It brings new meaning to the phrase 'shark attack'.

While most people will be familiar with images of seals being violently smashed out of the water snatched in the jaws of a shark, it appears some are exacting their revenge on the ocean predators.

Scientists have reported multiple cases of cape fur seals attacking blue sharks off the coast of South Africa.

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Scientists have reported multiple cases of cape fur seals attacking blue sharks and eating their guts 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 attacking the torpedo-shaped sharks

The seals, which are normally prey for great white sharks, have been seen attacking and killing medium-sized blue sharks, devouring their guts before leaving the rest of the carcass.

Divers also report seeing the fur seals attacking other species of shark and rays.

The behaviour has left marine biologists baffled as to why the seals, which normally hunt smaller fish, have turned to attacking 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 preying on such a large predator.

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 eating the guts 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 preying on such a large predator. 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 eating the guts 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 prey of larger sharks,and blue sharks have been observed pursuing juvenile and adult male Cape fur seals, though no kills 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 attacking 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.'

CAPE FUR SEAL VITAL STATISTICS Length: Males typically grow up to 7.5ft (2.3 metres) Weight: Males weigh 440 to 660lbs (200 to 300kg) Weapons: Large canine teeth, powerful jaws and claws Normal prey: Mainly fish but also about a fifth of their diet is squid and sometimes crabs Behaviour: They can live up to 30 years and then to gather in small groups but will often swim alone. They can dive as deep as 200 metres (650 feet) and stay underwater for seven minutes. They are commonly attacked by great white sharks, which attack them from below, and killer whales which hunt them in packs. Advertisement

BLUE SHARK VITAL STATISTICS Length: Females grow between 6 to 9.3ft (1.82 to 2.82 metres) Weight: Females weigh 205 to 401lbs (93 to 182kg) Weapons: Multiple rows of triangular serrated teeth Normal prey: Bony fish, cuttlefish, octopus, shrimp and crabs Behaviour: Their sleek body shape makes them fast and efficient swimmers, allowing them to snatch their prey out of the water. Blue sharks live for up to 20 years, are known as an open water species, and often migrate long distances. They are preyed upon by larger sharks like the great white and tiger shark. Advertisement

Fur seals have been known to mob great white sharks in large numbers but this is thought to be a defensive tactic to scare them away from breeding colonies.

In this case the fur seals have been observed attacking 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 prey 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 attack 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 overly react to the seals 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 attacking 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 attacking such a large and heavily armed predator is a high risk strategy if simply looking for food.