THE REPTILES OF FINLANDAbstract of the article:
Marika Rökman: Suomen luonnonvaraiset matelijat, Herpetomania vol.5.no.3-4/1996 pp.5-13.
Please refer to the original article published in Herpetomania.
After the Ice Age, when the ground revealed again the animals started to spread to Finland. The spreading of the reptiles was regulated by the climatic conditions and the land connections over the sea. First the Baltic ice lake developed near the edge of the ice. Then it turned into an arctic sea gulf called Yoldia sea, connecting with the Atlantic ocean about in the middle of Sweden. After the connection broke, the Yoldia sea turned into the Ancylus lake. The Ancylus lake period was quite short. There was now a land connection from the Central Europe to the Southern Sweden. But to Finland there were land connections from eastern and southeastern directions, through which the first reptiles came to Finland.
The Slow Worms (Anguis fragilis) and Viviparous Lizards (Lacerta vivipara) spread to Finland from southeastern direction and from south through Sweden. The two populations met in Northern Sweden between the parallel latitudes 62o and 64o. Because the different populations had been isolated during the ice age, their genetics were different. Even today the Slow Worms can be diveded into two populations by inspecting their spots, the structure of their ear openings and the scales of their heads. The snakes probably came through the same route, but they - especially the Grass Snake (Natrix natrix) could also have swum or floated over the Gulf of Finland or through Ahvenanmaa, the big island between Finland and Sweden near the Finnish coast in the south. The Smooth Snake (Coronella austriaca) could have came to Ahvenanmaa this way or either with the ships.
After the Ice Age 5000 BC the climate began to warm up. The average temperatures rose and the falls became longer. The reptiles lived much norther than they do today. There could have also been species that no longer live in Finland. For example in Sweden and in Denmark the European Pond Terrapin ( Emys orbicularis ) was quite common, and even in the 19th century there lived the Aesculapian Snake ( Elaphe longissima) in Denmark.
The Zoological Museum ( part of the Finnish Museum of Natural History) has done studies on the changes of distribution and population densities in the herpetofauna of Finland since 1960. According to the information gathered 1974-79 all the reptile species in the Southern Finland seems to became rearer. Comparing the study to the information gathered in 1980-92, the population density of the Viviparous Lizard seemed to be similar than it used to, but the population densities of the Common Viper ( Vipera berus), Grass Snake ( Natrix natrix) and the Slow Worm ( Anguis fragilis) seem to diminish. There are several reasons.
There is more traffic, and reptiles are also killed on the roads. The increased inhabitation also brings changes to the environment, that are effecting the reptiles. Especially this is seen when summer cottages are build on untouched forest and lakesides. The migration from the countryside to cities and towns is however leaving for example lots of fields uncultivated, which makes wonderful environment for the reptiles.
There are five reptile species in Finland, of which four ( all except the Viper) are protected by law since 13th May 1983, so wild caught animals should not be held in captivity either.
All reptiles in Finland hibernate because of the rough winter. At the autumn they find themselves a special place for hibernating. It must be deep enough to prevent the animals from freezing, but it must not be so deep that the temperature gets so high the animals don´t get their bodies to hibernate but rather starve to death. And if the place is too deep in the ground, there is a possibility it might be filled with ground water in the spring and so the animals would drown. The prefect place for hibernating is in southern Finland about 0,5 m under ground and in northern Finland about 1,5 m. The hibernation lasts in average from September to April.
Viviparous lizard (Lacerta vivipara) is the most northern lizard species in the world. It is the only species in Lacertidae, that is viviparous. In warm summers the lizards are born in beginning of July, but in cold summers they might be born late in July or even in August. Those ones born in August are rather small and they might not make it through the winter. Viviparous lizard is the most common reptile in Finland.
Slow Worm (Anguis fragilis) is the other of the two lizard species in Finland. It lives under the 63o30´ parallel of latitude. It is also viviparous.
Smooth snake (Coronella austriaca) is one of the three snakes found in Finland. It can be found in Finland only in Ahvenanmaa. The females mate every two or three years in Sweden, and that is how it probably is with the finnish snakes too.
Grass Snake (Natrix natrix) is the only reptile in Finland that lays eggs. It lays eggs in moist places like piles of manure or leaves. The Grass Snake can be found in the southwestern part of Finland, in the south coast and in the lakes areas up to the 62nd parallel latitude.
Adder or Common Viper (Vipera berus) is the only poisonous snake found in Finland. It is very dangerous only to small children, old and weak people and those who are allergic to viper poison, but every one who has been bitten must see a doctor immediatelly. Last time a Common Viper caused a death in Finland was in 1984. The female vipers mate only every two years, which is common for snakes near the northern limits of their living areas.
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