The natural world is full of wonder and mystery, there is still so much we, as humans, have to discover, learn about and fully understand in order to be able to live in harmony with the other inhabitants of this planet.
Watching animals in the wild, in their own natural environment is fascinating, the behaviours they exhibit and we as humans observe can be misunderstood and the signs of their presence left behind can be misinterpreted.
Over the course of a year we regularly receive notifications of a variety of different animals washing up on beaches around our coastline. And at this time of year, particularly from August until November we are often notified of seals and seal pups on our beaches, a perfectly natural and expected occurrence. However, over the past few months we have been notified of a number of grey seal remains washing up on beaches around the south and west Wales coast all with similar looking injuries.
But what is causing this to happen?
Grey seals are amongst the rarest on the planet, half the world’s population are found around the British Isles and that includes around the Welsh coast. We would ordinarily expect a higher number of seals, in particular seal pups, to wash up on our beaches at this time of year, it is the grey seal pupping season and seal pup mortality is generally considered quite high. Approximately 1 in 5 pups die before they are weaned, the main reasons being natural mortality, predators and bad weather – it’s a tough life!
This year a number of the reports we have received have included photographs or descriptions of seal bodies with what can only be described as chunks missing from them and those people reporting them curious as to know what has caused such injuries.
To understand what is causing these markings we rewind back a few years to 2009 when two adult bull seals on Skomer island were observed killing seal pups around the island. Seal pups with the same distinctive type of injuries were observed in subsequent years (2010 and 2011). Prior to these incidents on Skomer Island the scientific community were largely unaware that grey seals exhibited cannibalistic tendencies with only a few anecdotal incidents documented prior to 2009.
Then in 2014 researchers on the Isle of May, Scotland observed an adult male grey seal catching, killing and eating five weaned seal pups. A further nine carcasses were found in the same area, all exhibiting similar injuries. Research from the Netherlands indicated that grey seals were also preying on harbour porpoises and such incidents have also been documented in other parts of Europe and off the Pembrokeshire coast on four separate occasions in 2014.
Further research shows that this sort of behaviour has however, been exhibited by grey seals for a lot longer than originally thought. Since the early 90’s large numbers of dead seals with characteristic spiral lesions were being found washed up around the North Atlantic, these injuries had previously been attributed to interactions with ship propellers and shark predation however, the witnessed attack by a bull seal on the Isle of May and subsequent investigations enabled researchers to establish that those characteristic corkscrew injuries were actually caused by another grey seal.
Such behaviour could be attributed to infanticide, sexual frustration or the search for a potential food source. However, definitive reasons for such behaviour in grey seals is unknown, it is likely to depend on the individual seal themselves, local circumstances and to involve a variety of other factors.
In conclusion the injuries observed on some of the seals washing up over the last few months are the result of one or more bull seals predating on other seals in the area.
Sarah Perry, Living Seas Manager