Invasive alien species in Switzerland - Schweizer ...

An inventory of alien species and their threat to biodiversity and economy in Switzerland FOEN 2006 52
2.3 Reptiles – Reptilia
Three snake species have been relocated within Switzerland, from southern locations to
colder, northern localities. Two of these relocations were very local. The reintroduction
of the European pond terrapin used alien genetic material. The only alien
reptile species in Switzerland as a country are aquatic turtles released from aquariums,
but they seem not to have established populations yet (Table 2.4).
The case of the Italian wall lizard (Podarcis sicula (Rafinesque-Schmaltz)) in Switzerland
is rather mysterious (Hofer et al., 2001). It is not known whether the species is
native or alien nor is it proven that an established population exists at all. Since specimens
were found along the railway tracks in the Ticino, an accidental introduction
from Italy seems likely.
The dice snake (Natrix tessellata (Laurenti)) is one of the most endangered snakes in
Switzerland, because it is at the north-western limit of its range (thus it is naturally
rare). It is native to the Ticino, but was released north of the Alps at several lakes
(Gruschwitz et al., 1999). Although it is rare in Switzerland, it should not be relocated
to the north of the Alps. At the Lac de Genève, where it now occurs together with
another rare snake species, the viperine snake (Natrix maura (L.)), it is probably competing
with the native species for food and habitat, since the two species have a rather
similar biology, one occurring in south-western Europe and the other in south-eastern
Europe (Hofer et al., 2001).
Small populations of the western whip snake (Coluber viridiflavus (Lacépède)) might
have established at the Neuenburgersee and in the Valais, from specimens collected in
the Ticino and released in these areas. The impacts of these populations are probably
negligible and the populations themselves might not persist. Populations of the Aesculapian
snake (Elaphe longissima (Laurenti)) at the Neuenburgersee and Bieler See
may have originated in the same way and again have little impact. The latter species
does seem to be established (Hofer et al., 2001).
The status of the European pond terrapin (Emys orbicularis (L.)) in Switzerland is
not yet resolved (Hofer et al., 2001). Some populations might still be native, but there
were many re-introductions of the species. In most instances the origin of the specimens
released is not known, but releases of non-native material could lead to genetic
introgression into possibly surviving native populations. However, this concern remains
hypothetical because of the lack of knowledge of the status of extant populations.
The North American red-eared slider (Trachemys scripta (Seidel)) (see Fact Sheet) is
representative here of a guild of potential IAS – aquatic turtles from several genera. In
past years, several countries restricted the importation of this species, because of the
potential threat. However, this merely leads to a shift to other species by the aquarium
trade. The red-eared slider is still the species most often found in the wild in high
numbers and many places, although, because of the direct releases in parks etc., the