Grey seals

The population of grey seals at Lundy

The size of the grey seal population at Lundy varies during the course of a year, with the highest number of individuals occurring around pupping time (August to October). The table below sets out some of the recorded number of grey seals at Lundy over the years. Up until recently, these counts have been undertaken on an ad hoc basis with varying methodologies and at different times of year. Standardised monitoring of grey seal numbers was initiated in 2011 and is now undertaken on an annual basis. This is a requirement of the island’s SAC designation, the grey seal being listed as an Annex II species, meaning that it is recognised as a qualifying feature of the SAC.

In 2016, a modified count methodology was followed for the first time (as set out in the Marine Monitoring Handbook, written by Warden Beccy MacDonald in 2015), so the data produced could be compared to the results of counts of other grey seal colonies elsewhere in Britain, as coordinated by the Sea Mammal Research Unit at St Andrews University, Fife. In order to count the number of grey seals present around Lundy, the island’s coast has been is now divided up into 46 segments (Ellis, 2022). Repeat counts can take place on several occasions during the autumn, when seal numbers are likely to be at their highest. Members of the island’s Conservation Team (and willing volunteers) are tasked with undertaking the counts within allocated costal segments, all starting at a predetermined synchronised time. Recorders are asked to distinguish males, females, juveniles and pups. Most recently, count-trials using a drone have been undertaken which appear to reduce disturbance to the seals.

Table. Grey seal numbers from random years, indicating the gradual increase in numbers at Lundy since 1954.

The continued increase in numbers of the grey seal population at Lundy is likely to be restrained by one or more of the following:

• The availability of suitable haul-out sites around the island, which are progressively becoming ‘busier’;
• The limited number of secluded beaches and suitable caves where pups may be born;
• Autumn storms and gales (particularly easterlies) which will sweep pups from beaches before they can swim, leading to them being drowned;
• A limit to the amount of food (primarily fishes, crustaceans and octopus) available close to the island;
• ‘Overcrowding’ at Lundy is likely to result in individuals departing the colony and seeking to integrate into other colonies scattered around the coasts of southern and eastern Ireland, the Irish Sea, south Wales, the SW peninsula of England, the Isles of Scilly and the NW coast of France (Brittany).

Where to see seals at Lundy?

Grey seals may be encountered all around the island during most of the year, but there are always more to be seen close to the coast along on the east side of the island than elsewhere. Whilst spending a lot of their time swimming (either playfully or in hunting mode), all seals like to relax and snooze too, particularly either side of low water. It is at these times when rocks on the lower shore are exposed and it is here that most snoozing takes place.

Once out of the water, seals find it hard to move around and thus become more wary of threats and they remain alert, ready to move back into the sea at the slightest hint of danger. It is very easy to disturb hauled-out seals, so please keep your distance from them. The MPA’s Code of Conduct has a special section about how you should behave in the presence of seals, so please read it carefully and abide by its requests.

The most popular haul-out sites for grey seals at Lundy (after Jones, 2017). The size of the circle indicates the average number of seals counted at the site during survey visits.

Photo-identification of individuals

The patterning on a grey seal’s coat (its ‘pelage’) is unique to that individual, remaining the same throughout its life. Consequently, the patterning can be used to identify individuals, particularly from the areas around the head, neck and upper body. A database of ‘mugshots’ of Lundy’s seals is maintained by the Warden and shared with the Cornwall Seal Group Research Trust. The Trust has its own database of seal photographs taken all around the SW peninsula, with new photographs being compared to others to see if matches can be made.

Photo identification match. All of these photos, taken between January 2007 and September 2018, are of the same seal. Note for positive identification, it is important to obtain photographs of both sides of the head and nape. Photos reproduced from Jones, 2018 

Counting pups

‘Pupping’, the period when pregnant cows give birth to their offspring, takes place during the autumn months. Over the years, grey seal pups have been discovered on Lundy’s remote and secluded areas of foreshore from June right through to February, although the peak pupping times are between September and November (Jones, 2017).

Cows usually give birth to a single pup, although very rarely twins may be born. The mother will feed her pup on a very rich milk, allowing the pup to fatten up quickly, thereby providing important buoyancy and insulation. The pups are weaned after 2-3 weeks, after which they shed their white pelt and take on their grey pelage.

The bulls are not involved in parental care. Once weaning is completed, cows will mate with a dominant bull. Dominant bulls will act as ‘beach masters’ overseeing a harem of cows and chasing off any other bulls. They will mate with several cows within their harem, the gestation period being about 10-11 months.

Up until the early 1960s, Lundy’s grey seal cows were only thought to give birth to their pups at the end of a single cave, Seals Hole, located on the south coast. This cave extends at least 65 m into the granite cliff and has a dog-leg layout (see Mills (1968) for full description). Since the 1970s, with seal numbers increasing, many more pups have been born each year, some at established and visible pupping sites and others finding small, secluded beaches. The island’s main pupping sites are shown on the figure below.

The distribution of sites where grey seal pups were discovered during surveys carried out in 2017 (after Jones, 2017)

Interaction with other colonies

In the early 1960s, Hook (1963) suggested that Lundy’s adult seals may depart the island in order to visit other known breeding colonies after early August. Possible colonies were given as Ramsey and Skomer islands (60 mls & 45 mls to the NW); Cardigan Bay (100 mls to the N); the north coast of Cornwall (45-60 mls to the S); Isles of Scilly (100 mls to the SW); Saltee islands (100 mls to the W). However, he saw no reason why they should depart Lundy’s shores and head off to these other colonies.

In recent years, many of these routes have been confirmed through the recognition of individual seals using either tags or photographs of their patterning. Individual identifiable seals have been found to travel throughout the south-west, as well as northwards to the Isle of Man, across to southern Ireland and even as far as Brittany during their lifetimes. Several have been shown to return to Lundy at pupping time.

Learning more about grey seals

In August 2019, the St Helen’s Centre was delighted to host a visit of a skeleton of a bull grey seal, brought over to the island by the Cornwall Seal Group Research Trust. The skeleton is of a bull seal named Septimus who, when alive, was a well-known individual to the Trust and to volunteer seal-spotters from Cornwall’s south coast.

Following several years of being regularly sighted Septimus, in April 2015 Septimus was found washed up on a Cornish beach dead. As he had a history that was known to Trust volunteers, and to Rob Wells in particular who had made most of the sightings of him, it was decided to try to make some educational use of his skeleton. This required his corpse to be buried in soil and miraculously, after a couple of years, almost all of the flesh had disappeared from his bones.

The bones then needed careful cleaning followed by an expert in seal anatomy arranging them all in the correct place. By carefully wiring the bones together, the complete skeleton was re-assembled. Custom-built boxes allow for the skeleton to travel for exhibition purposes, with volunteers on hand to tell Septimus’ story.

We are pleased to support the work of the Cornwall Seal Group Research Trust, with whom the Conservation Team on Lundy have worked closely over the years. The Trust has recently published a small booklet about Septimus and we would recommend buying it (it sells for just £3). More details can be found here.

Search ‘grey seal’, ‘Halichoerus grypus’, ‘grey seal pupping’, ‘grey seal pups’ in the Bibliography for more reports on grey seals at Lundy since the mid-1950s.