well this can be interesting for the greens in future

"
Grey seals kill porpoises and could attack humans, scientists warn
Swimmers have been warned to keep clear of grey seals after scientists discover that they attack and kill porpoises

By Sarah Knapton, Science Editor

11:55PM GMT 25 Nov 2014

Grey seals may be a danger to swimmers after scientists discovered they were responsible for the widespread slaughter and mutilation of North Sea porpoises.

Wildlife experts have long been divided over what caused the horrific injuries seen on the bodies of hundreds of beached harbour porpoises. Some blamed boat propellers while others claimed the animals had become entangled in fishing nets and left at the mercy of scavengers.

Now DNA analysis of their injuries has led to an intriguing conclusion. It seems they are regularly attacked and killed by grey seals which tear strips of nutritious blubber from their bodies.

And scientists have warned that the seals could target human swimmers in a similar way.

Over the past decade more than one thousand severely scarred and wounded porpoises have washed up on North Sea coastlines.

“A substantial proportion of harbour porpoises that stranded on the Dutch coast were mutilated by grey seals,” said lead researcher Mardik Leopold of the Institute for Marine Resources and Ecosystem Studies in The Netherlands.

“Most cases involved active killing and that only a small proportion can be attributed to post-mortem scavenging. This makes predation by grey seals one of the main causes of death in harbour porpoises currently stranding in The Netherlands.

“Many of the mutilated porpoises were found on Dutch shores used frequently by human bathers and surfers and there would appear to be no reason why humans may not be at risk from grey seal attacks.”

Grey seals can grow to nearly 11ft in length and weigh 880lbs. There are large colonies in UK waters including at Donna Nook in Lincolnshire, the Farne Islands off the Northumberland coast, Ramsey Island off the coast of Pembrokeshire as well as large populations on the Scottish islands of Orkney and North Rona.

Although only a few mutilated porpoises have ever washed up onto British shores, experts say it could be just a matter of time before the behaviour becomes widespread, and pose a real danger to humans.

“Very few have been found, and recognised for what they are, in the UK,” added Mr Leopold.

“Yet, most grey seals live in Scotland, and so do many porpoises, and we know that grey seals sometimes swim from the UK to the Continent.

“It could be just a matter of time, of course as this behaviour is now very common here.”

Researchers looked back at images of 1,081 dead porpoises which washed up between 2003 and 2013. Of the 721 animals which were fresh enough to look for marks, some 25 per cent showed visible signs of attack by grey seals. They were also compared to three porpoises which had seal DNA in their wounds. The bites and scratches were found to match.

The scientists estimate that at least 17 per cent of animals washed up on shore were killed by the seals adding that many more bodies are likely to have been lost at sea or eaten completely.

Richard Harrington, of the Marine Conservation Society said: “Grey seals can be very territorial and we would always tell people not to approach them. Scuba divers often report being approached by seals.

“I have never heard of any attacks on bathers but you can’t rule it out.

“We have had lots of reports of carcasses of harbour porpoises where we have been unable to explain their deaths or their condition and this report gives a feasible explanation.”

The authors suggest that grey seals may have originally scavenged the bodies of porpoises which had become entangled in fishing nets and drowned, before moving to actually hunting the animals.

A spokesman for the RSPCA said swimmers should take care when in the water near seals.

"While we would urge people not to be unduly concerned by this study, it is important for people to remember that seals are wild animals and are therefore by their nature unpredictable.

“We would advise members of the public to be cautious around them however its unlikely these animals would pose an immediate threat to humans in the sea.

"Generally, seals do not directly interact with people and are naturally wary of humans. Like many other members of British wildlife they shun human contact.

"If a member of the public find a seal in distress we would urge them to contact rescue organisations such as ourselves where trained handlers can respond.”

The research was published in the journal Proceedings of the Royal Society B."

http://www.telegraph.co.uk/earth/wildlif...tists-warn.html

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of course the greens dont care for human's but to safe the beloved porpoises there could maybe one day a "Whale Protection Hunt" on grey seales

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bespoken only as a theory here in 2012

"Did Grey Seals Mutilate Two Harbour Porpoises?
by Ed Yong

Here’s the face of a grey seal. Aw. Doesn’t it look adorable? Remember, however, that seals evolved from bear-like ancestors and are part of the (mostly) flesh-eating group of mammals called carnivorans. If you look inside its mouth, you’ll find strong canine teeth. And Jan Haelters from the royal Belgian Institute of Natural Sciences thinks that those teeth did this to a harbour porpoise:

This poor animal was one of two harbour porpoises that washed up onto the Belgian coast in September 2011, three weeks and thirty kilometres apart. Both were freshly dead and still bleeding from huge wounds. Witnesses saw the strandings and reported them to local authorities. Haelters was at the site within an hour.

Both porpoises were young males with extensive injuries. The first, shown in the photo above, is obviously missing its throat. The second (click if you really want to see) was even more badly injured, with skin and blubber ripped from its belly. Both animals were also riddled with a series of smaller cuts and punctures.

None of these wounds are consistent with a man-made cause, like nets, fishing gear or boats. An animal, then. There are plenty of sharks in the area, but none of the wounds looked like a shark bite. Dolphins have been known to batter porpoises to death but they do not kill to eat. Their porpoiseless slaughter (I’m very sorry) results in pulped internal organs, rather than substantial missing flesh.

Instead, Haelters thinks that the pairs of short, parallel, curved punctures on the animals were inflicted by canine teeth. Foxes prowl the beaches but only at night—these porpoises washed up during the day. Dogs fit the bill too, but Haelters argue that there are no stray dogs in the area and that domestic ones aren’t allowed on the beach at that time of the year. Besides, people saw the stranded animals and officials got to the bodies quickly. Someone would have noticed if a dog was gnawing away at the carcass.

That leaves just two culprits, both of them seals. The gap between the paired punctures—four to five centimetres wide—rules out the smaller harbour seal. By process of elimination, Haelters thinks the grey seal must have killed the porpoises.

Male grey seals are formidable animals that can weigh up to 350 kilograms, and Belgian lifeguards did spot several “very large seals” close to the shore in the summer of 2011. These animals eat fish, crabs, squid, and even sea birds on occasion. They grab onto large fish like salmon and cod with the claws of their front flippers while flaying skin and flesh with their teeth—a feeding style that could easily have produced the injuries seen on the dead porpoises.

If Haelters is right, there’s something oddly poetic about the otherwise grisly story. Whales and dolphins evolved from deer-like hoofed animals while seals, as I said, are carnivores that have taken to the sea. A seal eating a porpoise is a modern marine episode in a longstanding conflict between a group of (mostly) predators and a group of (mostly) prey.

But Kathryn Ono, who studies marine mammals at the University of New England, says that the case is circumstantial, and that Haelters has too readily dismissed the possibility that dogs inflicted the wounds. “Is it possible that grey seals attacked the porpoises? Yes. Is it conclusive? No,” she says. “They would need either an eyewitness, or seal DNA in the wounds. [Even] with DNA, they cannot be sure if the porpoises were bitten post-mortem or were killed by the seals.”

So, no habeas porpoise for the grey seal yet (I’m really very sorry). Ono also points out that harbour porpoises are much faster than grey seals. Haelters raises the same question, but notes that porpoises often rest or move slowly at the sea surface, and grey seals can sometimes act as ambush predators. The two porpoises were also not in the best of health—their blubber was thin and they had lots of parasites. Perhaps they were too weak to react quickly to a surprise attack.

However, Haelters cautions: “We would like to warn against blindly extrapolating this cause of death to all other cases of heavily mutilated harbour porpoises found recently along southern North Sea shores.” Indeed, if grey seals really did kill the porpoises, it seems they only started recently. More than 600 harbour porpoises have been stranded on Belgium’s beaches since 2000, and not a single one has the same pattern of injuries as these two individuals. There are some cases from the Netherlands that fit the bill, but only since 2006. Haelters notes that the grey seal population in the North Sea has gone up dramatically in the last decade, so increasing competition could have spurred them to try out new delicacies.

Erich Fitzgerald from Museum Victoria in Melbourne agrees that the evidence is circumstantial. “It points to the possibility that grey seals in the North Sea have a much wider dietary repertoire than typically thought,” he says. “The next step in testing this hypothesis is a wider examination of other mutilated small cetacean carcasses as well as at-sea observations of grey seal feeding behaviour.”

“I would not make a big deal out of it until someone actually sees an attack, and if it is a common occurrence, then that will come soon,” adds Ono.

Update: Haelters got back to me with some responses to the criticisms. On the issue of whether the animal could have been bitten after death, he says that they found several signs of haemorrhaging, “indicative of wounds inflicted on a live creature”. He adds, “Cutting or biting into a dead animal does not provoke blood being pressed into the surrounding tissue – this was the case at several locations in both animals, and was clearly evidence of wounds being inflicted on a live porpoise.”

On the suggestion that he tests for seal DNA, he says, “We have at least thought of this, but after consulting with specialists, it became clear that – as everything happens in an aquatic environment – that any trace of seal DNA from the salive of the seal would have been washed away in the water before stranding, and that it would be very unlikely to find some.”

Reference: Haelters, Kerckhof, Jauniaux & Degraer. 2012. The Grey Seal (Halichoerus grypus) as a Predator of Harbour Porpoises (Phocoena phocoena)? Aquatic Mammals http://dx.doi.org/10.1578/AM.38.4.2012.343 "

http://phenomena.nationalgeographic.com/2012/12/20/did-grey-seals-mutilate-two-harbour-porpoises/