The Grey Seals of the Dee Estuary get ready for winter
As we batten down the hatches for winter an exodus of our largest marine mammal, the grey seal, is taking place from the tempestuous sandbanks of the Dee Estuary. Cheshire Wildlife Trust's Tom Marshall discovers the astonishing reason why
Seals, it seems, have got it made. Like a lot of large mammals they’ve turned lounging about for long periods into a necessary daily routine, something most of us at least, have not yet been able to make a lifestyle choice.
The sight of hundreds of seals ‘hauled out’ – a description most people probably wouldn’t appreciate when gracing the beach, is rather apt for an animal that can weigh in at 300 kilos. The Atlantic grey seal and the scarcer – and so rather mis-named – common seal, can be seen along much of our coastline, and Hilbre Island in the Dee Estuary is no exception.
A wind-swept trip out to the sandy fingers of Hilbre – facing defiantly into whatever the Irish Sea can throw at it – often assures a close encounter with the local grey seals as they casually pop their heads above the waves to check out the odd shaped brightly-dressed mammals on land.
But while much of the year offers this intimate opportunity, as the grip of winter starts to tighten, the seals disappear. It’s time to have babies.For the seals of Hilbre, there simply aren’t the suitable beaches they need to have their pups, so a journey to elsewhere in the UK is in order.
Ramsey Island along the Pembrokeshire coast is a typical destination, although it is still largely a mystery where many of our seals head to.This winter shift to traditional breeding haunts runs rather like a clock around the UK, with seals arriving in Wales in September, Scotland’s seals rolling up in October, and the east coast’s seals being last to the party as late as November. As the seals are tied to a return to our shores to raise a family, it makes them the largest breeding land mammal in the UK.
With such harsh conditions to contend with, the first few weeks of a young pup’s life are filled with one thing and one thing only, getting fat. The young pups need to put on two kilos a day – about 10 per cent of their birth weight – and are given a diet of 60 per cent fat milk.
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Although that impossibly soft snow-white coat of pup fur lasts forever on a thousand posters and calendar pages, in reality the furry jacket lasts just ten days, before the young seals gradually grow into their grown-up swimsuit of dark grey or black mottled fur.
Why grey seals make these journeys of hundreds of miles to raise their young is to secure the perfect location to bring up the family in peace. Although sand, shingle and rocky beaches are all acceptable, crucially, breeding sites must be above the high water mark and in some cases may range up to 300 metres inland.
As if looking after the newborns wasn’t enough for the female grey seals, the same areas also see male seals on the lookout for a partner. Such is the demand for the opposite sex, fights among male seals can regularly break out, with aggressive bouts often resulting in horrific-looking wounds to their necks and scars that last a lifetime.
Although their haul-outs and breeding colonies suggest a rather gregarious lifestyle, seals are in fact quite content in going their own way, with mothers and pups in breeding colonies usually maintaining a respectable distance from their neighbours.
After a few short weeks however, the draw of the surf becomes too strong and breeding areas once again fall quiet as the seals head underwater where they are truly in their element.
Seals can spend up to 40 per cent of their time out at sea, with foraging trips lasting between two and five days – matching that of many of the fisherman whose boats they pass silently underneath, safe in the knowledge their fishing skills are equally matched. Grey seals can be underwater for up to half an hour, diving as deep as 200m. At this depth, light is it at a premium, so seals often rely on their large whiskers to detect prey when their eyesight is stretched to the limit.
For the pups who may only be a few weeks old, the journey begins and although many will return to areas close to their birth to raise their own family, one Hilbre Island seal has even been recorded in the Western Isles of Scotland, hundreds of miles from the sands of the Dee or the rocky coast of Ramsey Island.
Wherever they return to, you can be sure that our grey seals will always be there to keep a close eye on us every time we’re down on the shore – whatever the weather.
Scaling up the challenge
Cheshire Wildlife Trust has been overwhelmed by the response to its Petition Fish campaign to protect the UK’s oceans, and in particular the Irish Sea. Around 2,000 people have already ‘signed a scale’ in the region at events ranging from the Cholmondeley Pageant of Power to the Blue Planet Aquarium, with schools and MPs also coming on board to support the campaign.
After months of intense meetings with stakeholders across the North West, 16 proposed Irish Sea Marine Conservation Zones have now been submitted to the Government for consideration under the Marine Bill. The Wildlife Trusts are continuing their campaign across the UK to secure these ‘nature reserves of the sea’ and safeguard a healthy and sustainable future for marine wildlife and people alike.
Find out more at www.wildlifetrusts.org.
The print version of this article appeared in the December 2011 issue of Cheshire Life
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