The isolated location of Gotska Sandön has resulted in a scarcity of mammals. Alpine hares and bats are the only land-dwelling mammals that live there. Grey seals are the most common water-dwelling mammals that visit Sandön and its surrounding waters, but as far as we know reproduction in the area is low. Seal Point (Säludden, on the island’s north-eastern side, is a sealprotection area where no admittance is allowed at any time of year.
BIRDS
The greatest numbers of birdlife on the island are during spring and early summer, when Gotska Sandön is crowded with sea birds, waders and passerines to name a few. Mostly land birds stop to rest on the island. However conditions are not the best for the resting birds since sweet water is scarce and the late hatching of insects results in a shortage of food for the insectivorous species of birds.
In the early summer a multitude of small bird species can be observed on Gotska Sandön. Parrot crossbills are among the most common. Their young hatch as early as March when the supply of pine cone seeds, the birds’ main source of food, is at its peak.
There are no large numbers of birds of prey, partly because of the lack of rodents. Even the species of nesting birds on the island are relatively few. Among the birds that do nest here are common eiders, mallards, oyster-catchers, goosanders, herring gulls, lesser black-backed gulls, common terns, wagtails, hawfinch, parrot crossbills, hobbies, shrikes and others.
Insect life on Gotska Sandön is special from several aspects. Despite the limited occurrence of biotopes there are numerous insects, of which most are connected with pine forest with a long continuity or to open sand. Some were found for the first time on Sandön, several also hove their sole Nordic occurrence here. This is the case for seven beetle species, for instance, all linked to pine forests. One of the island’s most interesting butterfly species, the grey horisme aemulata, is most often a characteristic mountain species commonly found in the Urals and Alps as well as in one location on Gotland. It is relatively common on Gotska Sandön, especially in the sparse pine forest around Arnagrop. However there are few mosquitoes, horse-flies and gnats thanks to the lack of fresh water pools where their larvae can hatch.
INSECTS
The open sand offers a very special habitat with an extreme micro-climate in many aspects, mainly because the open sand surfaces are exposed to strong sun’s rays and wind creating a dry habitat. Even the fact that the moisture-binding plant and humus cover is very thin or non-existent contributes to the dry milieu. This leaves its mark on the insect life which is unusually rich in heat-craving dry land species, for example the sand hymenopter|an and other aculeate which dig their larvae chambers in the sand and do their hunting in the immediate surrounding area and beetles that spend the day buried in the sand and go out to hunt at night. Countless ant-lions, represented by two species, bury their funnel-shaped trap-pits in the sand where they then lay buried in wait for their prey.
The fact that there are so many beetle species on Gotska Sandön is largely due to the aged pine forest that grows naturally with dying and dead trees in different stages of decomposition. Even the different types of decomposition, i.e. different kinds of fungus, bacteria, insects and other organisms, are important to the coleoptera. Most of the island’s threatened species of beetles on live on or in the dead wood of the pine forests.
Some of the more common species are metallic wood-boring beetles, rose-chafer, hairy longicorn beetles and small rhinoceros beetles. The most common theory of why so many rare, heat-loving species live on Gotska Sandön is that they are relics from the post-glacial tropical period. Another theory is that logging has not depleted the forest in the same way as it has on the mainland thanks to the fact that it has been less intensive and that parts of the forests have been protected since 1910, as well as that the frequent forest fires have kept the forests open and contributed to the occurrence of a great many substrates. Probably it is a case of a combination of several factors.
