External Anatomy, Reproduction, Distribution 
pecially surrounding Halle, Saale, Jena, Weimar 
and Erfurt. It can also be found in smaller num- 
bers in Western Europe (particularly in parts of 
France, Belgium and The Netherlands). This spe- 
cies is also scattered in the Ukraine, Rumania and 
southern Czechoslovakia. The most northern limit 
of its occurrence, which appears to be at a latitude, 
of about 60 degrees, is in the U.S.S.R. (Serebrenni- 
kov, 1930; Saint Girons, et ai, 1968; Hannoun, 
1974; Vohralik, 1974). In its western ranges, it is 
limited strictly to rural districts with loess soil. In 
addition to the typically colored European hamster, 
albino, black and transitionally colored animals can 
also be found, though only rarely (Petzsch and 
Petzsch, 1970). Petzsch and Petzsch (1956) report- 
ed that black hamsters are dominant over non- 
black animals; this fact explains the increase in 
number of these hamsters in some areas around 
Thuringen (Zimmermann, 1969). C. cncetus lives 
only in small well-defined areas (Fig. 1-18) within 
these regions; however, the incidence of the species 
is high. 
Annually, variations in the number of these ham- 
sters are observed and presumed to be seasonally 
dependent; sometimes the animals become so nu- 
merous that they are a scourge to the land. Geo- 
graphically, they are abundant in rural areas 
bordering highly industrialized regions, especially 
those where predominately summer and winter 
grains as well as root crops are planted. The Euro- 
pean hamster prefers ground that is heavy, clayish, 
and not too damp — ground appropriate for build- 
ing burrows with depths varying from 30-60 cm in 
summer to more than 2 m in winter. Each burrow 
has several exits with tunnel diameters approxi- 
mately 8-9 cm. This species lives primarily on 
plains not more than 400 m above sea level (Petzsch, 
1936,1937). 
Due to the proximity of heavily industrialized, 
thickly populated districts with relatively high en- 
vironmental pollution, wild European hamsters 
from these areas have special interest for research 
on "spontaneous" cancer and respiratory diseases. 
3 
