As the ice receded
following the last ice-age, some 10,000 to 12,000 years ago, Shetland was
left isolated without any link to the Scottish mainland. As a consequence
man has been responsible for introducing all Shetland’s terrestrial
mammals to the islands, either deliberately or accidentally -
even the Otter is likely to have been
introduced, perhaps by the Vikings who may have
realised the value of the pelts for clothing.
Some of these introduced
mammals may be having a serious impact on Shetland’s breeding birds. Feral
cats, polecat-ferrets and hedgehogs are all known to eat ground-nesting
birds or their chicks and eggs.
At present we do not have an
accurate picture of the distribution or population of any of Shetland’s
mammals. The Shetland Biological Records Centre needs your help to try and
resolve this situation. Please help by filling in the survey form on the
back of this leaflet with your sightings and returning it.
stoat is believed to have been introduced into the islands in the 17th
century. Although rarely seen, it is thought to be widely distributed
throughout Mainland. Rabbits, young blue hares and ground-nesting birds, are
likely to form the major part of its diet in Shetland. Be careful not to
confuse stoats with their larger cousin, the polecat-ferret, a recent
introduction into the islands, but one that presents a far greater threat to
our native fauna. Stoats are much-smaller, less than one foot (30 cm) long.
They have a longish tail, which always has a dark tip. In summer, the coat
is two-tone, chestnut brown above, contrasting with yellowish-white from the
chin to the belly. In winter many turn white, but they still retain the
blackish tip to the tail.
The blue hare, also known as
the mountain hare, was first introduced to the Kergord estate in 1907.
Subsequent introductions have taken place on Ronas Hill and on the island of
Vaila. Shetland, with its abundance of heather moorland, and comparative
lack of predators, is well suited to this species. It has now spread to
several areas on Mainland, although its precise distribution is poorly known
and there is little information on numbers. The only similar species is the
rabbit. Blue hares are best identified by their larger size, longer,
black-tipped ears, longer legs and bounding gait. Some turn partially or
totally white in winter.
otter is perhaps Shetland’s most popular mammal, especially with visiting
tourists. Globally, otters have suffered a dramatic decline throughout much
of their range, although there have been recent signs of recovery in some
areas. In Shetland the population is thought to number around 1,000
individuals, making it important in an international context. Shetland’s
otters need a combination of soft peat (for excavating their holts),
freshwater (for cleaning salt from their coat), and offshore kelp beds (for
feeding). Although we know they are distributed right around the coast of
Shetland, many areas have never been surveyed properly. Shetland’s otters
have a shorter life expectancy (just 3 years) than their Mainland
counterparts, which means that the population could fluctuate markedly over
a relatively short period of time.
were introduced to the Tingwall Valley in the middle of the 19th century.
They thrive in Shetland in the absence of any predators, of Mainland and
been and have spread through much introduced to many of the inhabited
islands. While much of their food comprises earthworms, beetles, spiders and
slugs they also have an appetite for bird’s eggs, so they present a threat
to ground-nesting birds. Hedgehogs have often been observed systematically
working their way through all the nests in a tirrick colony. By
recording hedgehogs throughout the year we may also build up a better
picture of their hibernation habits in the islands.
Other land mammals found in
Shetland include rabbits, polecat-ferrets, house mice, field mice and brown
rats. Occasionally vagrant bats from the British mainland or the continent
find their way here too. SBRC also welcomes any
records of these other mammals which will help build a clearer picture of
their status and distribution. With a common species, like the rabbit, there
is little to be gained from recording individual sightings. It would,
however, be very useful if you could tell us which one kilometre squares you
have seen rabbits in. These can be identified from OS Maps by a four figure
grid reference (e.g. HU 1750 would represent the
one kilometre square that includes the Loch of Watsness).
At present polecat-ferrets
are only known to occur on Mainland. If you see
any on other islands we would ask you to contact us urgently. It may be
possible to eradicate them there before they become a persistent problem as
they have done on Mainland.
ALL your records help, even those of
animals found dead on the road.
your records to :
SBRC, Shetland Amenity Trust, Garthspool,
Lerwick, Shetland. Tel. (01595) 694688.