The attack, confirmed by marine investigators, marks the first documented case of a grey seal killing a common dolphin in Welsh waters, according to multiple reports. The dolphin carcass washed up at Newgale beach in late February, and a forensic examination revealed a pattern of spiral lacerations around the dolphin's middle, consistent with a seal biting through to the underlying fat layer and exposing the organs beneath.
Seals ranging across the stretch of sea between south Wales and the Devon and Cornwall coasts are the prime suspects. Earlier in January, witnesses observed a grey seal holding a common dolphin in its jaws in the Irish Sea off Dublin. Devon waters also saw two comparable incidents before the year was out. Across the British Isles, researchers have now reportedly linked 20 named individuals to this type of attack, each identified through the unique scarring on their faces.
Britain's grey seal population has recovered from roughly 500 in the early twentieth century to around 120,000. Scientists trace the roots of dolphin predation to cannibalism among seals. Male seals compete fiercely for mates between September and January, going without food throughout. Studies suggest some seals began targeting pups as a source of sustenance, tearing into the fat beneath the skin and moving on without consuming the rest.
Scottish researchers monitoring the behaviour over ten years recorded the rate of grey seal cannibalism doubling and then some between 2015 and 2016. Cannibalism among seals was first observed in Canadian waters in 1992, off the coast of Nova Scotia. Seals are no match for dolphins in open water, as dolphins are significantly quicker.
It remains unclear how many grey seals are currently exhibiting dolphin-killing behaviour, and the exact mechanism by which the hunting technique is spreading among seals is not known. Whether the grey seal population will continue to grow and lead to more such attacks, and what impact this behaviour will have on common dolphin populations, are open questions.