Corkscrew Seal Lesions
Two seals found on the same stretch of beach in 2009 were juvenile harbour seals (Phoca vitulina). Three seals examined in 2010 were pregnant adult harbour seals.
The key pathological findings were consistent in all five seals suggesting a common cause. All had corkscrew-shaped wounds originating on the left hand side of the mouth and spiraling in a single, clean-cut continuous wound around the head and neck to end midway down the body. In every case, the wound spiraled clockwise when viewed head-on.
The carcasses were relatively decomposed, however it is considered the seals were alive when the injuries were sustained. With this degree of trauma it is likely death was instantaneous.
Seal skin is tough and these animals showed a single unbroken clean cut, angled at about 35 degrees towards the tail. The cut extended onto the ribcage but did not cause rib fractures or trauma to underlying harder body structures. The juvenile seals examined by SMRU exhibited cuts through the bone of the skull. (see picture)
The blubber and connective tissue had been 'peeled' off the underlying skeleton, indicating powerful shear forces were involved in addition to the cutting process.
There was no evidence of any underlying disease process in any of the seals examined. Blubber thickness was normal for the time of year in all cases. The stomach of one animal had a large amount of partially digested fish showed it had recently fed.
The seals we examined were either juvenile or heavily pregnant. It is possible animals in these groups have different feeding behaviors, or are slower than normal.