Invasive alien species in Switzerland - Schweizer ...

2 > Vertebrates – Vertebrata 39
urban areas, the normal habitat in Central Europe, the environmental impact is probably
less pronounced, although it is an additional omnivorous predator. However, its
impact on structures and foodstuffs and its role as a disease vector in human settlements
are unambiguous and the brown rat is controlled in many cities.
The raccoon (Procyon lotor (L.)) (see Fact Sheet) is the only member of the family
Procyonidae introduced to Europe. It was introduced from North America and released
in Germany in 1934. From that and other subsequent releases, it spread through Germany
and reached Switzerland in 1976. The spread continues and it will eventually
inhabit the lowland parts of Switzerland to Genève in the south and the Valais. The
impact of the species is disputed. A definitive conclusion cannot be reached without
studies being carried out in Switzerland to assess its impact on the native wildlife and
as a vector of diseases (Hohmann et al., 2002). This addition to the native fauna may
have to be accepted, since control measures are not very effective and its impacts have
not (yet) been demontrated. If incidences of diseases carried by the raccoon increase,
hunters will have to focus more on this species.
The only introduced dog (Canidae) in Central Europe is the east Asian raccoon dog
(Nyctereutes procyonoides (Gray)) (see Fact Sheet), which was for decades and at
many places in the former USSR extensively released as a fur animal. The acclimatization
of the species and the value of the fur are questionable. However, it spread westwards
and recently reached France. Incorrect identification based on field observations
by laypeople may be frequent, because they are not familiar with this species and it can
be confused with other predators, such as the raccoon. Thus, identification of dead
animals is the most reliable way of evaluating its spread through Europe. Opinions
about its impact vary between it being a benign species and a species causing severe
impact on native wildlife. One argument is that, as a generalist on abundant food
resources, it does no harm to rare organisms. Others argue that predation on bird
species and amphibians might have a negative impact (Kauhala, 1996). The status of
many amphibians as endangered in Central Europe and the fact that amphibians were
found in proportions of up to 45 % in the diet of the raccoon dog (Barbu, 1972) indicates
the potential harm. It also plays a role as a vector of diseases to humans and other
predators (Weidema, 2000). It is recommended that the spread of the raccoon dog
should be monitored and its impact in Switzerland evaluated. However, a control
programme seems unlikely to achieve success, because of the raccoon dog’s secretive
behaviour and its continuing invasion from the East. The raccoon dog and the raccoon
are two additional predators with which native animals have to cope. Thus, although
the impacts of the introduced predatory species are not so different from those of native
origin, if they add to the total predator load, they are likely increase the predatory
pressure, and destabilize existing populations and population cycles.
The only established alien deer (Cervidae) in Switzerland is the sika deer (Cervus
nippon Temminck). It is a fairly small deer species, intermediate in size between the
native roe deer (Capreolus capreolus (L.)) and red deer (Cervus elaphus L.). The
summer coat is chestnut brown to buff brown with white spots, while it is uniform
grey-brown during winter. The rump patch is white with a black upper border and the
white tail has a black stripe. The typical antlers have four points each. The sika deer is