Top 10 fascinating facts about Northumberland’s grey seals

The first seal pup has been born on the Farne Islands this year.

The first seal pup has been born on the Farne Islands this year.

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The first seal pup of the year has been born on the Farne Islands, off the north Northumberland coast.

Following the new arrival, the Islands’ resident rangers will start their annual seal count. Every year, more than 1,500 pups are born on the islands, which are one of the largest Atlantic grey seal colonies in England with a population estimated at 5,000.

A grey seal.  Picture: The National Trust

A grey seal. Picture: The National Trust

1. The National Trust and seals on the Farnes

Seals have been being tagged on the Farne Islands since the 1950s. The Farnes boast the longest data set of any colony with work started by the Natural History Society of Northumbria in 1952 (counts had been undertaken long before this but were only on certain islands). The Trust took over counting in 1970 and continue to this day. 1,575 pups were born in 2013 – this equates to a colony size of 5,500 based on multiplying the number of pups born by 3.5.

2. Seal data

Male – grows up to 2 metres in length and weigh 230kg. Their lifespan is 20-25 years. Female – 180cm in length, weight 150kg, lifespan 30-35 years. Grey seals feed on wide variety of fish, squid and octopus. They spend 80% of time below water, 20% on the surface breathing. Seals dives last 4-8 minutes, although the maximum time dive was recorded at 30 minutes. Seals can reach depths of 30 metres.

3. Counting the pups

Given the right weather conditions, colonies are visited every four days and new pups marked, on the rump, with a harmless vegetable dye. Using a rotation of three or four colours, we can work out how many pups are born, how many die on the colony, and how many ‘disappear’ before they would be able to survive. This gives us the number born annually and allows us to calculate the mortality rate.

4. Storms

Rough weather can be devastating for seals, particularly those from the north which can scour pups from some of the low-lying islands causing mass deaths. However, as seals move back onto Staple and Brownsman to pup – islands less prone to wave-wash – we are seeing a reduction in storm-related losses.

5. Twins

What would have been a ‘world first’ – Grey seal twins – was reported from Brownsman Island on October 23, 2012. All the photographs looked good; only one cow ever seen in attendance, both weaned successfully by 16 November, Sea Mammals Research unit heavily involved. Although DNA samples were taken and whilst close, they were not 100% conclusive. Everyone on the Islands would have sworn they were twins – but the scientific evidence does not fully back this up. With more DNA samples it might have been possible to prove but unfortunately we can’t!

6. The first few weeks

30% of pups are dead within a month and 50% within their first year. Pups are weaned in 18 days, in which time they will have quadrupled in weight. Abandoned by mother they can spend another 20 days or so on the colony before heading out to sea for an independent life with no parental involvement.

7. Tracking

The first experiment in tracking seals was on December 16, 1951, when ten pups were fitted with metal cattle tags. One was found alive at Jaeren, 20 miles away from Stavanger, Norway, on December 30. The pup travelled 400 miles in a maximum of 14 days. This was the first clue that seals moved across the North Sea. Things have since moved on. The Sea Mammals Research Unit fit pups with their own mobile phones with sim card and number. They text in every two days and some also have GPS tags to give their position hourly. Whenever in range of mobile phone transmitter, they phone home and all data downloaded Farnes seals are regularly recorded on the Dutch, German, and Norwegian coasts.

8. Monks and seals

From the 12th century onwards, the seals were ‘exploited’ by the monks being regularly sent to the parent house at Durham. They were valued because of the oil that could be extracted from their carcasses and also as a luxury food. As creatures of the sea, seals counted as ‘fish’ and so could be eaten on a Friday. In 1378-79, a seal calf could fetch about 22p which works out at about £40 in today’s money. From documents through to the 1500s, there was quite a trade in seals and seal products.

9. The Farnes and other colonies

This is the largest colony on east coast of England, although Donna Nook, Lincolnshire, occasionally overtakes us with Norfolk colonies rapidly growing too. 2.5% of the annual British pup production is from the Farnes, compared to 20% from the Monach Islands in the Outer Hebrides – the largest British colony.

10. Other seal species

Very small numbers of Harbour/Common (same species) seals can be found on Lindisfarne, with small numbers around Teesside, then larger colonies around the Wash. They are very rare on the Farnes, with an average of one recorded per year.

Thanks to Nick Lewis of The National Trust. Visit http://www.nationaltrust.org.uk/farne-islands/wildlife/