Grey seals on Blakeney Point
Blakeney Point is home to England's largest breeding grey seal colony with over 3,000 pups born each year.
With sandy beaches backed by dunes, no natural predators and very little disturbance, Blakeney Point is the perfect place for grey seals to live and give birth. They can be seen on Blakeney Point all year round, but between late-October and mid-January, large numbers congregate to give birth and breed.
The first grey seal pup was spotted on Blakeney Point in 1988 with only occasional pups born throughout the 1990s. With five born in 1999, numbers have been increasing year on year. In 2014 Blakeney Point became the largest grey seal colony in England. And then in 2019 we reached a new record, with 3,399 pups on the reserve.
Scientific name: Halichoerus grypus means ‘hook-nosed sea pig’.
Brief history: Seals are thought to have evolved from otter-like ancestors on the shores of the North Atlantic around 15 million years ago.
Size: Adults can reach up to two and a half metres in length and weigh up to 250kg. Bulls (males) have longer noses, are larger and darker than cows (females).
In the wild, female grey seals can live up to 35 years whilst males live for about 25 years. Bulls reach sexual maturity at six years whilst cows are a bit earlier, at three to five years. They moult their fur annually in the spring, after the breeding season and have a thick layer of blubber to keep them warm, which can be up to six centimetres thick. This blubber is built up during the warmer months and can be used for energy when required, such as during the breeding season.
Cows become fertile soon after weaning their pups. Bulls hold territories and those that are dominant may mate with over six cows. Protecting a harem is a full-time job, with males often not feeding for several weeks. Mating can take place on land or in water and sometimes sneaky non-dominant bulls will mate with a cow, while the dominant bull is mating with another of his harem.
Pregnancy in grey seals lasts for eleven and a half months with the first three and a half months being delayed implantation. This delay gives cows time to feed up and moult after pupping.
The first British pups are born off the Isle of Scilly and Cornwall in August and then follow a clockwise pattern north to Scotland and down to England with the Norfolk colonies being the last to start pupping at the end of October, early November.
Cows give birth to a single pup, weighing around 13.5kg (twins are very rare, the only proven case being at Horsey in 2015). Pups are born with a yellow coat, which turns white after a couple of days.
For the first three weeks, pups will feed up to six times a day, for up to ten minutes at a time. The milk contains around 60% fat, helping pups grow very quickly, gaining about 2kg in weight each day. Pups are then weaned at around three weeks of age, weighing between 45 to 50 kilograms. It's at this point they shed their white coat.
One of the sadder aspects of the job
Every year, sadly several grey seal pups don't survive the first three weeks of life. Those three weeks are an important time in a seal pup's life, as it's the nursing period when they remain on land, as they're unable to swim until their white coat has been replaced with waterproof fur. This rate of mortality is typical of grey seal colonies. After the rest of the colony has returned to sea, the team have the tough task of reviewing the site and deciding whether to carefully remove any carcasses which might put other species at risk due to attracting scavengers, such as the fragile tern colony. Others are left to degrade as part of the natural process to benefit other species in the food chain.
Grey seals will mainly eat fish but have been known to also eat crabs. They locate food by sight and sound, but they also have incredibly sensitive whiskers which can help detect vibrations given off by fish swimming. Because of this, even blind seals can survive.
Relationship with man
Commercial hunting for their skins began in the eighteenth-century, however, by 1914 there numbers were dwindling. Grey seals were the first British mammal to gain protection and the Conservation of Seals Act (1970) gave them further protection, to allow numbers to recover.
Grey seals are found on both sides of the Atlantic Ocean with the eastern side holding two thirds of the world's population. As well as being found in the United Kingdom, they are also present in Canada, Norway, Iceland and Russia, often on islands and in caves.
Largest rookery in World: Sable Island, Nova Scotia, off Canada (100,000)
Second largest: Monach Isles, Outer Hebrides, West coast Scotland (10,000)
Blakeney Point was the 11th largest in the World in 2015 (2,343).
Globally there are approximately 400,000 grey seals.
The number of pups born on Blakeney Point has increased significantly since the first pup was born on the reserve in 1988. It was first ackowledged as an established colony in 2001 with the birth of 25 pups. Since then nearly 20,000 pups have been born on Blakeney Point.
So, what numbers are we talking about?
Year Pups Increase
2007 297 39%
2008 433 46%
2009 603 39%
2010/11 789 31%
2011/12 973 23%
2012/13 1248 28%
2013/14 1614 29%
2014/15 2453 52%
2015/16 2372 -3%
2016/17 2403 1%
2017/18 2700 12%
2018/19 3012 12%
2019/20 3399 13%
Why has the population increased so dramatically at Blakeney Point?
The population increase at Blakeney Point is likely due to the following reasons:
- They have no natural predators - for example killer whales.
- Blakeney Point is a remote location with little disturbance from visitors.
- There is a lot of space for them to breed and also sufficient room for them to spread as the colony increases in size.
- Grey seals are often found on rocky shores which pose a threat to pups who can get washed away or bashed against the rocks in stormy weather. In these locations the mortality can be as high as 50% (sometimes even higher if there are significant storms). However, at Blakeney where it is a shallow sloping beach with sand dunes, the seals aren't faced with these risks and during stormy weather and high tides they can move into the dunes to prevent getting washed away. For this reason the mortality rate at Blakeney is less than 2% which means over 98% reach weaning age.
- Around half of all grey seals born will reach their first birthday so that is a significant number of seals surviving into adulthood at Blakeney Point.
- Seals born at Blakeney Point in previous years are likely to be returning to breed when they reach sexual maturity.
- There is sufficient food for them to feed in the North Sea.
Other east coast breeding colonies
There are three other significant breeding grey seal colonies on the east coast of England:
- The Farne Islands, Northumberland (National Trust) - 2,737 pups (2018)
- Donna Nook, Lincolnshire (Lincolnshire Wildlife Trust) - 2,186 (2019)
- Horsey/Winterton-on-Sea, Norfolk (Friends of Horsey Seals) - 2,316 (2019)