Scientists baffled by mysterious 'corkscrew' deaths of seals off British coast
- Thread starter Joe
- Start date
I did some research on the web on this but couldn't come up with any solid conclusion so far. Looking at the picture, they look mechanical made more then predator made. From one forum i visited, I will not post it here as it is not recommended, someone came up with this ;
Could be it, or some other new propulsion system unknown yet to the public, new submarine technology or as others taught Marine Current Turbines or Giant tidal turbine.
Here a link with pictures of bow and stern thruster.
http://www.google.ca/images?hl=en&client=firefox-a&rls=org.mozilla:en-US:official&channel=s&q=bow+thruster&um=1&ie=UTF-8&source=univ&ei=qdZvTNTfBcP98AbembjqCw&sa=X&oi=image_result_group&ct=title&resnum=4&ved=0CDgQsAQwAw&biw=1024&bih=521
Could be it, or some other new propulsion system unknown yet to the public, new submarine technology or as others taught Marine Current Turbines or Giant tidal turbine.
Here a link with pictures of bow and stern thruster.
http://www.google.ca/images?hl=en&client=firefox-a&rls=org.mozilla:en-US:official&channel=s&q=bow+thruster&um=1&ie=UTF-8&source=univ&ei=qdZvTNTfBcP98AbembjqCw&sa=X&oi=image_result_group&ct=title&resnum=4&ved=0CDgQsAQwAw&biw=1024&bih=521
I saw a documentary on UK channel 5 last which adequately explained this mystery I think. Basically the effects are due an attack by a greenland shark and the corkscrew pattern results in the way the skin unravels - essentially following the line of least resistance. This particular species of shark also has a different arrangement and type of teeth to other sharks from what I could glean from the program. Film was shown of one shark attacking a seal corpse in a decidedly peculiar fashion. Fairly convincing stuff as an explanation to this mystery, osit.
More on the program here, although the video now seems unavailable -
http://www.five.tv/shows/nature-shock/episodes/nature-shock-the-seal-ripper
From Wikipedia -
There is now an argument suggesting that the Greenland is responsible for 'Seal Ripping' attacks on grey seals.[12] These attacks cause a corkscrew pattern of cuts and tears which spiral around a seal's body, following the grain of the collagen within the muscles and running at 45 degrees to the seal's body. Seal deaths have been occurring over larger territories, including the north and east coasts of the UK, which suggests that the Greenland may be moving beyond its traditional habitat range.
Edit - extra info
It seems these corkscrew marks on dead seals have been recorded since the early 1990s
http://www.greenhorsesociety.com/sharks/shark_predation.htm
Quote
"In the early 1990s, there was a marked increase in the number of seals killed by sharks in the waters around Sable Island. Each year since then, a few hundred carcasses of shark-killed seals - grey, harbour, harp, hooded and ringed seals - are found washed ashore on Sable Island. A study of shark predation on seals has been underway on the island since 1993 and selected results are reported in several publications (see Additional Reading, below). A final manuscript, in collaboration with Lisa Natanson (Apex Predators Group, National Marine Fisheries Service, Narragansett Lab, Rhode Island), is in preparation.
Shark predation on pinnipeds - seals, sea lions and fur seals - is a well- documented phenomenon. Shark-inflicted mortality may be a significant factor in the biology and behaviour of many pinniped species, influencing, for example, diving patterns, timing of breeding season, length of suckling period, and population dynamics. Reported shark predation on pinnipeds most often involves great white shark Carcharodon carcharias (e.g. California and South Africa) and tiger shark Galeocerdo cuvier (e.g. Hawaii).
During the last twenty years actual shark attacks on Sable Island seals have been witnessed only a dozen times, most often from seismic boats working near the island. The observers were not able to identify the shark species involved. However, based on observations and specimens collected since 1993 - wound patterns, score marks on bone and tooth fragments - it appears that several species are responsible, including great white shark.
However, of the various wound patterns seen in the seal carcasses washed ashore on Sable Island, by far the most common is a peculiar clean-edged `cut' (termed "corkscrew") which is quite unlike wounds characteristic of attacks by great white, tiger and mako Isurus oxyrinchus sharks recorded elsewhere. Also, occurrence of the corkscrew wound peaks during winter - a season when such sharks are unlikely to be in the area. Thus, of the several shark species involved in predation on seals at Sable Island, at least one of them is not among the "usual suspects".
During the first year of the study it became apparent that the corkscrew wound was not consistent with what was then known of the predatory behaviour of various shark species. Photographs of the wounds were sent to seal and shark researchers in many countries including Norway, Scotland, Australia, New Zealand and South Africa, and to numerous scientists on the east and west coasts of North America. The amount of time spent in such `investigation' almost equaled the amount of time spent collecting data on the beach. Although none reported seeing similar wounds, many people shared information about predation and wound patterns observed elsewhere - all of which suggested that the nature and scale of shark predation at Sable Island comprised a unique, albeit perplexing, phenomenon.
As the study proceeded, consideration of the jaw and tooth structure of various sharks suggested that the species responsible for the corkscrew wound might be the Greenland shark Somniosus microcephalus. Discussions with Jack Casey and Wes Pratt (Apex Predators Group, NMFS) and review of historical documents supported this theory, and interviews with Nova Scotian fishermen confirmed that Greenland sharks were certainly in the Sable Island area. While much other `circumstantial evidence' has also implicated this species, until actual attacks are witnessed and documented, the role of the Greenland shark in predation on seals around Sable Island will be a matter of speculation, albeit well-founded speculation. "
More on the program here, although the video now seems unavailable -
http://www.five.tv/shows/nature-shock/episodes/nature-shock-the-seal-ripper
From Wikipedia -
There is now an argument suggesting that the Greenland is responsible for 'Seal Ripping' attacks on grey seals.[12] These attacks cause a corkscrew pattern of cuts and tears which spiral around a seal's body, following the grain of the collagen within the muscles and running at 45 degrees to the seal's body. Seal deaths have been occurring over larger territories, including the north and east coasts of the UK, which suggests that the Greenland may be moving beyond its traditional habitat range.
Edit - extra info
It seems these corkscrew marks on dead seals have been recorded since the early 1990s
http://www.greenhorsesociety.com/sharks/shark_predation.htm
Quote
"In the early 1990s, there was a marked increase in the number of seals killed by sharks in the waters around Sable Island. Each year since then, a few hundred carcasses of shark-killed seals - grey, harbour, harp, hooded and ringed seals - are found washed ashore on Sable Island. A study of shark predation on seals has been underway on the island since 1993 and selected results are reported in several publications (see Additional Reading, below). A final manuscript, in collaboration with Lisa Natanson (Apex Predators Group, National Marine Fisheries Service, Narragansett Lab, Rhode Island), is in preparation.
Shark predation on pinnipeds - seals, sea lions and fur seals - is a well- documented phenomenon. Shark-inflicted mortality may be a significant factor in the biology and behaviour of many pinniped species, influencing, for example, diving patterns, timing of breeding season, length of suckling period, and population dynamics. Reported shark predation on pinnipeds most often involves great white shark Carcharodon carcharias (e.g. California and South Africa) and tiger shark Galeocerdo cuvier (e.g. Hawaii).
During the last twenty years actual shark attacks on Sable Island seals have been witnessed only a dozen times, most often from seismic boats working near the island. The observers were not able to identify the shark species involved. However, based on observations and specimens collected since 1993 - wound patterns, score marks on bone and tooth fragments - it appears that several species are responsible, including great white shark.
However, of the various wound patterns seen in the seal carcasses washed ashore on Sable Island, by far the most common is a peculiar clean-edged `cut' (termed "corkscrew") which is quite unlike wounds characteristic of attacks by great white, tiger and mako Isurus oxyrinchus sharks recorded elsewhere. Also, occurrence of the corkscrew wound peaks during winter - a season when such sharks are unlikely to be in the area. Thus, of the several shark species involved in predation on seals at Sable Island, at least one of them is not among the "usual suspects".
During the first year of the study it became apparent that the corkscrew wound was not consistent with what was then known of the predatory behaviour of various shark species. Photographs of the wounds were sent to seal and shark researchers in many countries including Norway, Scotland, Australia, New Zealand and South Africa, and to numerous scientists on the east and west coasts of North America. The amount of time spent in such `investigation' almost equaled the amount of time spent collecting data on the beach. Although none reported seeing similar wounds, many people shared information about predation and wound patterns observed elsewhere - all of which suggested that the nature and scale of shark predation at Sable Island comprised a unique, albeit perplexing, phenomenon.
As the study proceeded, consideration of the jaw and tooth structure of various sharks suggested that the species responsible for the corkscrew wound might be the Greenland shark Somniosus microcephalus. Discussions with Jack Casey and Wes Pratt (Apex Predators Group, NMFS) and review of historical documents supported this theory, and interviews with Nova Scotian fishermen confirmed that Greenland sharks were certainly in the Sable Island area. While much other `circumstantial evidence' has also implicated this species, until actual attacks are witnessed and documented, the role of the Greenland shark in predation on seals around Sable Island will be a matter of speculation, albeit well-founded speculation. "
