Friday, 3 April 2020

H is for Halichoerus grypus (Grey Seal) and Harbour Seal

Please remember! We ask that people do not visit the Reserve particularly if you have to travel. All car parks on Holy Island are closed to visitors until government restrictions are lifted. Many residents on Holy island fall into the vulnerable category. Please adhere to these guidelines for the health and safety of yourself and others during this time.
When walking along the coastline of Lindisfarne National Nature Reserve you may catch the sound of ghostly singing floating towards you on the wind. In history, this song was said to be Mermaids luring ships to their watery graves on the reefs they were singing from but this was not the case. The sound they were hearing was in fact haul outs of seals calling to one another. Indeed, seals are closely related to the mermaid myth with Scottish mythology telling the tale of Selkies – seals that shed their skin to walk the land as beautiful women. This is so embedded in the culture of the Northern Isles that Selkies are the name Grey Seals in local dialect.

Lindisfarne National Nature Reserve supports a large population of up to 6,000 Grey Seals hauling out on the sandbars at low tide. They can be readily viewed around the Reserve throughout most of the year and are often very curious leading many people to be unsure about who is watching who!

Grey Seal being curious
 Harbour seals are also present on the Reserve but in much smaller numbers. Harbour Seals are smaller and have a bear like face in comparison to a Grey Seals long dog like snout.
Comparison of Common and Grey Seals
The Grey seals will spend most of their time on the Reserve moulting, feeding and sleeping. From late September most of the seals leave the Reserve heading to the Farne Islands to pup. Whilst being heavily pregnant the female will be also be incredibly fat having fed furiously throughout the summer months. This is because once she hauls herself onto one of the islands and gives birth she will not leave the pup for three weeks – not even to eat. During this time she expresses incredibly fatty milk to the pup, allowing the pup to increase in weight by 2kg per day until it is weaned. In reverse the female will halve in weight, looking like skin and bones. Once the pup is weaned the female will mate with a bull seal and leave the colony.
The Grey seal pregnancy is very different to a humans. Once mated in the colony and the cells begin to divide and develop, a blastocyst is formed and the pregnancy is paused. Then about 3 months later environmental cues tell the body to restart the pregnancy. This means that despite the gestation period being 9 months Grey Seals give birth at the same time every year. It is thought that this is so male and female seals only have to interact once a year and pups are bought into the world under at the optimum time of year.
Group of Grey Seals taken from a safe distance
Once restrictions are lifted and visitors are welcome onto the Reserve again we ask that you do not approach any hauled out seals. These seals are wild animals and can bite. They are also a carrier of many diseases. Disturbance also causes unnecessary stress to the animals. The guidelines are to stay at least 50 metres away from any seal and enjoy the spectacle from a far with binoculars.

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