Recently I was down picking winkles in Clare and came across a dead dolphin or porpoise with what looked to me to be 2 very big bites taken out of its back. I took some photos with my phone and was wondering do we have something in Irish waters that could do this. One of the bites took a chunk about a foot long if not more.John, Clare.
– These were most likely the work of bottlenose dolphins, more likely so if the cetacean you saw was a porpoise. In Britain, where more research has been done, the major cause of death of washed up porpoises in 2007 according to the Environment Ministry was bottlenose dolphin attack, especially in places where the two species occur together, often with deep bite marks similar to what you describe. Research in the early 1990s on hundreds of washed up harbour porpoises in the Moray Firth concluded that the damage caused to animals including broken ribs, internal organ rupture and bite marks was attributable to bottlenoses. There are also reported cases of bottlenose infanticide.
Science is at a loss to explain conclusively these occurrences; bottlenoses do not compete with porpoises for food and their actions may simply be a function of territorial behaviour.
This are the most likely explanations for what you saw, however I suggest you send your photographs along with a detailed description including location to the iwdg, the resident authority on such matters in Ireland, who will appreciate the data.