Monday, 24 August 2009

Cannibalistic Pinniped

Reading Cliff's account of the Grey Seal eating the dead Porpoise off Strumble Head reminded me of an incident I witnessed there whilst sea-watching on the 12th October 2006.
Just after 8am on that day I was gazing out to sea and saw the familiar head profile of a big bull Grey Seal a few hundred yards offshore. It looked as if it was devouring something and I thought at first that it might have been a conger Eel. I have previously seen a seal eating this formidable fish when I stayed on Skokholm island a few years ago. I looked through my scope at the animal and was quite shocked to see that it was actually chomping away at the carcass of a dead seal pup. This old bull was taking chunks out of the body of the pup and was clearly relishing it. The carcass of the seal was on its back and I could clearly see the forelimbs. The bull was making inroads into the carcass from the front end. The head of the pup appeared to be missing. There was a motley gathering of gulls (kittiwakes, black-headed & herring gulls) round about picking bits of flesh up from the sea surface. Curiously there were also a few shags and auks about too which were taking a passive role in the proceedings. The shags were occasionally peering under the water.
When I related this incident to Cliff Benson not long after he put forward a plausible theory with regard to the presence of these birds. He stated that predatory fish may have been attracted by this feeding frenzy hence therefore the presence of the shags and auks which would in turn feed on the fish.
After watching this gruesome spectacle for a while I then saw a considerable amount of blood emanating from the seal carcass which coloured the sea round about red. I saw the bull rip out what must have been the internal organs (viscera) of the dead pup possibly including the blood rich liver. This too was avidly devoured by the bull throwing his head back in the process. Now not long after this the bull seemed to be getting uncomfortable with the ever growing band of seabirds gathering around and he took a deep dive and that was the last I saw of him and for that matter the seal pup carcass too!
Following this incident I trawled through my extensive literature on seals at home to find any reference of cannibalism in this species and could find no mention of it. I think I can safely assume that the pup probably died of natural causes as there is generally a high mortality among young pups in the first few weeks following birth especially on these wild windswept exposed beaches of West Wales and that in this case the pup may have been washed off a storm battered beach or sucked out of a sea cave whereupon it drowned and then the old bull seal came across the floating carcass by chance.
I wonder if this was the same animal that ate the porpoise!
Truly a case of a mammal eating Pinniped!