Seals in Shetland
The
most numerous marine mammals in Shetland waters are two species of seal - the
Grey Seal and the Common Seal or Harbour Seal. The old
Shetland name for the Grey Seal is 'haaf fish' (deep sea fish), because it prefers
more open sea conditions, while the Common Seal is known as 'tang fish' (seaweed
fish) because of its preference for more sheltered shores and islands. Contrary
to expectations, there are fewer Common Seals than Grey Seals
in Britain as a whole,
with around 28,000 Common and 105,000 Grey. In Shetland the situation is
reversed with 6,000 Common Seals and 3,500 Grey Seals.
It is possible to age seals quite accurately by counting the growth rings
round the roots of the back teeth. Most of the information about how long
seals live comes from seals that have been kept in zoos. The oldest recorded
seal in the world came from Shetland, a grizzled old female who lived to the
ripe age of 46 years!
Seals have been around
Shetland for many years with bones found at the Jarlshof settlement dating
back to the Iron Age. There is also a lot of folklore surrounding 'selkies'
coming ashore having cast off their skins and been transformed into beautiful
people, and many an islander would fall in love with a 'selkie' and go back to
the sea with them, traditionally this only happened at midsummer. In years
gone by Shetlanders have hunted seals for their blubber, used for oil, their
skins which were used to make clothes, and occasionally the flesh would be
eaten. Most recently seals have been hunted for their valuable pelts.
Most valuable is the skin
of a pup, particularly of the Common Seal, or the adult just after moulting,
providing it had not been scared. The Common Seal was hunted the most partly
due to the fact that the pups were found on easily accessible shorelines and
also because until 1970 you did not need a permit to hunt Common Seal whereas
you did for Grey Seals. Seal hunting was particularly common after the Second
World War as times were hard and the demand for sealskins kept the prices
high. Between 1956 and 1967 the recorded number of Common Seals dropped from
428 to 141 at Fitful Head and, although the figures from elsewhere are not so
accurate, the same decline was seen throughout the islands.
It was about this time that a Seal Conservation Act (1970) was introduced
which meant a permit was required to hunt Common Seals and a closed season was
imposed from 1 June to 31 August when it is unlawful to injure, kill or take a
seal, with exceptions to this for seals killed in the vicinity of nets etc.,
to prevent them damaging fishing equipment and those seals killed under license
for scientific or management purposes. The following year, 1971, a
Shetland-wide survey showed that the numbers of Common Seals had fallen to
just 1800, there was also concern about the selective pup hunting which over
several years had resulted in an aging population and few females being
recruited to the breeding population each year. These concerns, resulted in
1973 in a total ban on hunting, which was revoked in 1998, following
scientific advice that seal numbers around Shetland had recovered following
the over-exploitation which had occurred decades earlier.
The diet of seals has been studied by bodies such as the Sea Mammal Research
Unit and Aberdeen University. Grey seals have been shown to predate heavily on
the sandeel, which is important in the diets of many marine animals in the
North Sea. Around the Outer Hebrides grey seal diets have been found to
contain more Gadidae fish (the cod-like fish) than around Orkney or the
Southern North Sea grey seal sites.
A local research project funded by the Shetland Wildlife Fund, Ministry of
Agriculture, Fisheries and Food, Scottish Natural Heritage, the Scottish
Association for Marine Science, the Hunter & Morrison Trust and the Shetland
Fishermen's Association have examined the diets of Common Seals around
Shetland. Analysis of droppings indicates which fish they eat, the size of the
fish consumed and how much of the commercially important species are being
consumed.
Grey Seal Halichoreus
griseus
The most numerous of the
seals in Shetland waters, this species is found around almost the entire
coastline although the largest numbers usually frequent the more sheltered
east coast. The last full survey of pupping sites in Shetland was carried out
in 1983 when a total of 1000 pups were counted which equates to c.3,500
animals in total.
The total U.K. population
was estimated as 108,500 in 1994, and of these 99,300 were found in Scottish
colonies. Good places to see this species are at Sumburgh Head where 500+ may
be hauled out on the rocks at the base of the cliffs during the summer, or
around Lerwick Harbour where they are opportunistic feeders around the fish
processing factories on the shoreline, although they may be found in most
sheltered bays and voes.
Grey Seals give birth to
their pups fairly late in the year, around October, usually on beaches at the
foot of cliffs. When the Grey Seal pup is born it has a white furry coat which
it sheds after about 3 weeks. At this time it is not a particularly proficient
swimmer. The pup will feed from her for about 16-21 days and during this
period and immediately after breeding, both the males and females do not eat
and can lose quite a lot of weight. Immediately after this they have a period
of feeding between late November and mid-January when they regain condition
and it is only then that they undergo their annual moult. Females tend to
moult in early February with the males later in mid-March and it is at this
time they spend long periods hauled out, though not at their breeding sites.
Common Seal Phoca
vitulina
The Shetland population
of the Common Seal was last counted in 1997 using the 'hi-tech' method of an
aerial thermal image survey of the coastline. A total of 6,000 were counted.
This is a minimum figure as only those animals hauled out on rocks are
recorded in this way, although this is thought to represent between 60-80% of
the total population.
The current UK
population estimate of the species is 28,000 animals. As with Grey seals the
species is found around the majority of the Shetland coastline although some
of the largest concentrations are around Fitful Head (south Mainland), the
isle of Mousa (where they are very easy to see), and the north Mainland
coastline.
Common Seals usually give
birth to their pups in June, hauled out on the shore between tide marks. The
pups have already shed their white furry coats before birth and are able to
swim well from birth. Common Seal mothers tend to be more attentive to their
offspring and will if necessary dive while holding onto the pup if threatened.
The pup will continue to feed from it's mother for about 4-6 weeks. The pup
will continue to feed from it's mother for about 4-6 weeks, at which point the female will become sexually receptive and mate with
a male, around this time or before, the mother will abandon the pup to fend
for itself. The peak of mating in common seals is visible at haul-out sites
such as on Mousa, there is a sharp rise in the incidence of mature males with
fresh bloody scaring on their necks and hind-flippers.
Common Seals begin moulting
during July and finish during September, females and young animals moult
first, followed by males and finally sexually mature males are the last to
undergo the moult during September.
Distinguishing between
Grey and Common Seals
Grey and Common Seals can
be quite difficult to tell apart, although with practice it can be reasonably
straightforward. Size is one factor distinguishing the two - Grey Seals are
usually much bigger with a fully grown adult male or bull reaching 2.2m in
length and weighing 220kgs, the females reaching 1.8m and weighing 150kg; the
fully grown male Common Seal only reaches 1.5-1.8m and weighs 113kg with the
female reaching 1.2-1.5m and weighing 113kg. There are also differences in the
colour and patterns of the fur, although this feature is extremely variable
and can vary with the sex, age, whether or not the fur is wet or dry and
whether the animal is moulting (shedding and replacing) it's coat.
Probably the easiest way
to tell them apart is the shape of the head. The Grey Seal has a much larger
head with a high muzzle often referred to as a Roman nose; whereas the Common
Seal has a low dog-like muzzle with a relatively rounded head and distinct
forehead producing a much more appealing and expressive appearance. The
nostrils of the Common Seal form a 'V' shape while the Grey's are much more
parallel. The difference between the two species is not limited to their
appearance, they also tend to have different habits.
Grey Seal
(left) and Common Seal (right) facial characteristics
What to do if you find
a stranded or injured seal in Shetland
Occasionally, seals may
become entangled in fishing gear and may suffer shock, which can kill them.
You can help by taking appropriate action: When seals become entangled in
fishing gear offshore, it will take patience and time to release them. It is
best done at the surface of the water so that the effective weight is less. If
the seal is caught in a trawl or drift net do not lift it out of the water on
to the deck if it appears to be active and alert, as it may suffer respiratory
collapse or cardiac arrest. Never tow a seal to harbour if this can be
avoided. Always ensure that all net and line has been removed from the seal
before releasing it.
Seals found stranded on beaches
are sometimes already dead, but may be injured. Look for wounds such as those
made by boat propellers or sharks. Young seals in particular may be exhausted,
disorientated or shocked. If you find a seal in this condition contact the
Hillswick Wildlife Sanctuary,
The Booth, Hillswick, Shetland. (01806) 503348, who will be able to advise or
arrange suitable rehabilitation.
Nature in Shetland
