The Small Mammals (Insectivora, Lagomorpha, Rodentia) of Bulgaria

Vassil Popov

Summary

Due to its geographical location and varied environment (climate, topography, vegetation), Bulgaria has a relatively rich small mammal fauna. After nearly 100 years of investigations by native and foreign scholars, 42 taxa have been recognized. This information is scattered throughout a vast body of literature. The main sources are of three types: 1) regional faunistic studies and taxonomic investigations of particular species; 2) studies of the regional foci of parasitic diseases; and 3) studies of the prey of raptorial animals (mainly owls).

Despite the relatively high number of publications on small mammal biology (more than 100 are cited in this report), many important knowledge gaps exist. Some geographical areas are insufficiently studied; consequently, the inventories of local species are incomplete. The taxonomy of groups containing closely related species has not been studied in detail; hence, the distribution and ecology of some of these species is poorly known. The actual conservation status of the rarest species in the national Red Data Book is unknown, and data on their ecology do not exist. Nevertheless, the published literature allows us to outline regional species richness and the regions containing rare and/or endemic species, and to designate the important or fragile habitats, ecosystems, and communities.

Two especially important territories are specified: 1) parts of the main mountain chains where the most species of small mammals are represented; and 2) low-land territories where steppe (Dobrudzha, the northern Black Sea coast) and Mediterranean (the southern Black Sea coast, the Strouma and Mesta River valleys) small mammal faunal elements can be found. The sensitivity of, and possible threats to, small mammals and their habitats are analyzed. The lowland habitats, because of their declining area and the destruction of the natural corridors between them, are of particular importance in this respect. Of the most important threats, special attention needs to be given to the isolation of natural habitats, the modification of the physical environment, the development of intensive forms of agriculture, pollution, and urban growth.

Studies of the evolution of the small mammal fauna since the Pliocene indicate that climatic deterioration and fluctuation during the Pleistocene are the main factors behind the present pattern of local distribution. Some species are relicts from the Pliocene (Myomimus roachi) or Early Pleistocene (Apodemus mystacinus) and are restricted to the southern-most parts of the country. By contrast, some rare species that occur mainly in north and especially northeast Bulgaria are remnants of a rich Late Quaternary forest-steppe fauna (Sicista subtilis, Mesocricetus newtoni, Cricetus cricetus, Cricetulus migratorius). During the Holocene the most important factor affecting small mammals has been the human impact on the environment. Increasingly intensive land use in lowland areas has considerably altered the natural habitats and their respective small mammal communities in these areas. Particularly vulnerable are steppe species.

The final section of this report presents several recommendations regarding small mammal conservation. It is important to establish a large network of protected areas. Special research on the distribution and ecology of the rarest species should be undertaken.

Introduction

The territory of Bulgaria is characterized by a high degree of climatic variability, due primarily to its geographical location and varied topography. A complex mosaic of mesoclimates, best understood in terms of local gradients of temperature and humidity, can therefore be found. These features combine to produce a diverse and heterogeneous landscape that, along with geological variation, provides for a wide range of habitats and a high degree of biodiversity. It is also important to emphasize that Bulgaria extends into the central part of the Balkan Peninsula, where the influence of several biogeographical zones can be observed. Consequently, Bulgaria represents the limits of the geographical ranges of many small mammal species. It can therefore be regarded as a territory of exceptional conservation value, enriching Europe with unique habitats and species and supporting a considerable proportion of the continent's mammalian fauna.

A Brief History of Small Mammal Research in Bulgaria

The first data on Bulgarian small mammals appeared in Chritovitch's (1892) work on pest animals. Kozarov (1909) addressed similar problems in a paper on the damage caused by the hamsters in Bulgaria. Of particular interest are Nehring's (1898a, 1898b, 1899, 1901) and Miller's (1903, 1910) investigations on the taxonomy of the golden hamster, mole rat, and forest dormouse. These works are of mainly historical interest, but it should be noted that the designation of the Bulgarian golden hamster as a separate species (Mesocricetus newtoni Nehring, 1898) has only recently become widely accepted.

The field work and materials collected by C. Anderson in Bulgaria provided the basis for the first monographic study of Bulgarian mammals, by B. Kovatchev (1925). Subsequent faunistic data were collected through the investigations of Boetticher (1925, 1933), Heinrich (1936), and Wolf (1940).

The investigation of small mammals entered a new stage after World War II and accelerated in the early fifties as studies became more regular and intensive. Special attention was given to regional faunistic studies of small mammals (Atanassova, 1978, 1981, 1990; Atanassov et al., 1982; Boev, 1983; Iotova, 1972; Markov, 1955, 1962b, 1964, 1968, 1974a, 1974b; Mateva and Christov, 1970; Mitev, 1973, 1980; Paspalev et al., 1952; Christov, 1961, 1974). Some of these studies were undertaken in connection with biomedical investigations of the natural foci of parasitic diseases (e.g., Kolebinova, 1974, 1978; Kojumdjieva, 1971a, 1971b, 1973, 1974; Mateva and Christov, 1971; Paspalev and Markov, 1962; Surbova, 1961, 1974; Ianchev, 1974).

These efforts led to a revision of the country's species inventory (Markov 1952, 1953; Paspalev et al., 1950; Peshev, 1955; Peshev et al., 1960; Peshev et al., 1960; Straka, 1964; Vohralik, 1985, 1991; Popov and Nijagolov, 1991). The wealth of materials and comprehensive information gathered during these investigations allowed for more detailed consideration of the taxonomy and distribution of particular species or groups of species (Markov, 1957a, 1957b, 1960a, 1960b, 1962a; Martino and Paspalev, 1953, 1956; Mitev, 1968, 1970, 1971, 1979a; Mitev and Peshev, 1977; Peshev and Hussein, 1990; Peshev, D., 1992; Peshev Ts., 1955a, 1969; Peshev and Angelova, 1985; Peshev and Iotova, 1961; Peshev and Mitev, 1975, 1979; Popov, 1981, 1982, 1993). In the last decade, special attention has been given to studies of the taxonomy of several species complexes using biochemical and cytogenetic methods (Beltcheva et al., 1977; Gerasimov et al., 1984; Gerasimov et al., 1990; Kral, 1975; Orsini et al., 1983).

Several recent investigations have centered on aspects of small mammal ecology, especially the population dynamics of pest species, dominant species in natural ecosystems, and other species of particular interest (Markov et al., 1972a; Markov et al., 1972b; Markov and Christov, 1975; Markov et al., 1978; Mitev, 1980; Petrusewicz et al., 1972; Straka 1967, 1965, 1966a, 1966b; Straka and Gerasimov, 1977).

Very important information on regional species composition became available through investigations of the diets of different animals, primarily birds of prey, and especially owls (Baumgart, 1975; Baumgart et al., 1973; Beshkov and Gerasimov, 1980; Michev et al., 1984; Simeonov, 1963a, 1963b, 1966, 1968, 1970, 1978, 1980, 1981, 1983a, 1983b, 1984, 1985; Simeonov and Boev, 1988; Simeonov et al., 1981; Simeonov and Petrov, 1986).

The Quaternary history of the Bulgarian small mammal fauna has recently become a subject of special interest (Kowalski, 1982; Popov, 1984, 1985, 1986, 1988, 1989; Popov and Gerasimov, 1988). Studies in this area have revealed the relationship between climatic fluctuations, environmental changes, and the evolution of particular phylogenetic lineages and small mammal communities (Popov, 1991). The patterns revealed in these studies allow us to understand the current distributions of the species and to predict changes in small mammal communities under increasing human environmental impacts.

Gaps in Knowledge

The distribution of species is of particular interest in the effort to protect biodiversity. The specific set of environmental conditions upon which an organism or group of interdependent organisms depends constitutes its habitat. Most habitats can be closely related to particular types of natural environments, where the association of an ecological community and the dominant vegetation can be identified. It is thus convenient to refer these associations to natural regions that show a high degree of uniformity in their environmental characteristics and their flora and fauna (Gruev, 1988).

The available knowledge on the ecology of small mammals indicates that, although they form a very heterogenous group from an ecological point of view, they have in common one very important feature: their small size. As a consequence of their small size, they are directly dependant on small-scale environmental factors. Hence, the local distribution of small mammals reflects primarily the character of vegetation, which in turn depends primarily upon temperature and humidity. Natural areas endowed with specific environmental conditions (climate, topography, and vegetation) may be expected to support a relatively homogeneous small mammal fauna.

Some summary works on various aspects of small mammal biology appeared after Kovatchev's 1925 monograph (Atanassov and Peshev, 1966; Markov, 1957; Peshev, 1975; Markov and Christov, 1974). However, in order to construct a comprehensive picture of the spatial distribution of species richness, it is necessary to draw information from other specialist sources and from disparate regional data. Some of these sources have been mentioned previously. Others are presented in the reference section without special citation in the text. In general, information about the current latitudinal and longitudinal distribution of small mammals in Bulgaria comes from three main types of sources: (1) regional faunistic studies of small mammals or taxonomic investigations of particular species; (2) studies of the regional foci of parasitic diseases; and (3) studies of the food habits of raptorial birds. The species distribution data extracted from these sources are compiled according to the natural areas listed in Table 1.

The available information suffers from certain gaps. Some of the conclusions, especially these presented in the last two types of sources, are doubtful. In particular, this involves the degree of discrimination within groups of closely related species (such as Crocidura leucodon/ suaveolens, Neomys fodiens/anomalus, and Apodemus sylvaticus/flavicollis). In this report the distribution of these species is presented according to extrapolations based on the present knowledge on their ecology and taxonomy (Popov, 1993; Aufrray et al., 1990; Orsini et al., 1983; Popov and Gerasimov, unpubl. materials).

On some occasions, very important faunistic findings are reported but not fully discussed, causing doubt about the veracity of these data. For example, Kolebinova (1978) in studying small mammals as hosts of trombiculid larvae in Ropotamo National Park reported a specimen of Clethrionomys glareolus. This species is usually restricted to the mountains. It occurs rarely in extensive forests at lower altitudes (below 800 m a.s.l.) in northern Bulgaria, but as a rule only in landscapes near the mountains. Such doubtful data are included in this review of the regional distribution of the small mammals, but they are given special designation (see Table 1).

The small mammal remains found in owl pellets pose similar problems. In these cases unusual occur-rences of particular species are probably due to long-distance transport from neighboring areas. These data are also specially designated in Table 1.

Analysis of the available information indicates that past studies have been unevenly distributed geographically. However, there is no correlation between the number of information sources for a given area and the established species number. It can thus be assumed that, in general, the regional species assemblages are relatively well known. Nevertheless, some of the species absences noted in Table 1 reflect omissions in the regional investigations rather than real biological causes.

In this regard, the distributions of the rarest species in the Bulgarian Red Data Book (Christov, 1985; Peshev, 1985; Peshev and Spassov, 1985) are of particular interest. A review of the available sources shows that they have been reported only once or twice in the past and no current information on their actual distribution and conservation status exists. There is an almost complete lack of information on the ecology of these species and the threats they face. Even in the last few years, several mammalian species not previously reported in Bulgaria have been identified (Vohralik, 1985, 1991; Popov and Njagolov, 1990). It can thus be assumed that the species list of the small mammal fauna is not definitively complete. There have been practically no investigations of small mammal communities or of the patterns in their composition along environmental gradients.

Current Assessment

Poorly Known Geographic Areas

Assessment of the information in Table 1 indicates that seven regions are insufficiently investigated: the eastern Rhodopes, the southern parts of the Maritsa and Tundzha River valleys, the eastern Stara Planina Mountains, the upper part of the Strouma River valley, Dobrudzha, the northern part of the Black Sea coast, and the mountains along the western border. These areas have been identified based on the low number of relevant information sources. Taking into account that, for many regions, the principal source of data has been owl pellets, the following areas merit special faunistic studies: the Danubian plain, the Predbalkan region, and the Kraishte-Konyavo region.

Species Richness

The list of Bulgarian small mammals contains 42 species. The number of species, including species associated with human settlements, per region (as defined above) varies from 16 to 27. Three areas contain more than 25 species: the eastern part of the Stara Planina Mountains, the Danubian Plain, and the southern Black Sea coast.

Rare Species

Some species, such as Neomys anomalus, Dryomys nitedula, Apodemus microps, Microtus epiroticus, show low abundance and discontinuous distribution. This, however, is likely due to their specific life histories or insufficient investigations (A. microps, M. epiroticus) rather than threat factors. These species probably inhabit many parts of the country.

Some species are confined to clearly delimited regions, but in these areas are relatively numerous. This group includes such species as Apodemus mystacinus, Microtus guentheri, Mesocricetus newtoni, Oryctolagus cuniculus, Chionomys nivalis, Mus spicilegus, Mus spretoides. The restricted ranges of these species reflect their specific ecological tolerances. Some are steppe species whose ranges are restricted mainly to northeast Bulgaria; others are Mediterranean elements in the Bulgarian fauna and are found in parts of southern Bulgaria where the Mediterranean climatic influence is greatest. Chionomys nivalis is a specialized high mountain dweller characteristic of the mountains in southern Europe and the Near East. In Bulgaria it is associated with the highest mountains.

A third group consists of species represented by small scattered populations at a limited number of sites: Suncus etruscus (the southern Black Sea coast), Sicista subtilis (Dobrudzha), Myomimus roachi (southeast Bulgaria), Cricetulus migratorius (scattered localities in northern and southern Bulgaria).

In general, the Bulgarian small mammal fauna contains few rare species, but some of the rarest are of particular interest within the European context. In this respect, steps should be taken to protect the fauna in Dobrudzha, the southern part of the Black Sea coast, and southeast Bulgaria.

Endemism

Generally speaking, the Bulgarian small mammal fauna is dominated by widely distributed species (European, Euro-Siberian, Mediterranean, Irano- Turanien, etc.) (Markov and Christov, 1974). However, two species, though not strictly Bulgarian or Balkan endemics, deserve special attention.

The main portion of the Bulgarian golden hamster's range is within the territory of northern Bulgaria. This species, Mesocricetus newtoni, may be considered an endemic for the Lower Danubian plain.

The other species, Myomimus roachi, is a relict of the relatively diversified Pliocene glirid fauna. This group of dormice is now reduced to only two vicarious species: Myomimus roachi and M. personatus. The current distribution of the first species is primarily in southeast Bulgaria.

Unique Ecosystems, Biotopes, and Communities

Because of its different climatic and topographic regions and the important influence of its mountain ecosystems, Bulgaria contains virtually all of the main classes of European habitats.

According to the CORINE (Coordination of Information on the Environment) classification, five selection criteria must be applied in identifying the most important natural and semi-natural habitat types: (1) habitat types characteristic of a particular large-scale biogeographical zone; (2) habitats characterized by natural ecological processes; (3) habitats that support a high level of biodiversity; (4) habitats with endemic or threatened critical species present; and (5) habitats of particular significance for migratory species. Within the scope of these criteria, the small mammals in Bulgaria of special interest are found in steppe habitats. As a rule these habitats are in part artificial and occur in some parts of northern Bulgaria, especially in Dobrudzha. Despite their semi-natural origin, they support some characteristic elements of the steppe biota, including several rare small mammal species (e.g., Sicista subtilis, Mesocricetus newtoni, Cricetus cricetus, Cricetulus migratorius).

Interestingly enough, some of the rarest and most threatened small mammal species tend to be confined to agricultural landscapes or territories highly influenced by human activity (the localities, for example, of Myomimus roachi, Suncus etruscus, and Cricetulus migratorius in southern Bulgaria). However, the intensification of land use may destroy these habitats. Thus, although these habitats are not of particular importance for other elements of the biota, they must be given special attention.

Prior to the introduction of agriculture, forests were the dominant form of climax vegetation in Bulgaria. In the lowlands, only small fragmented areas of natural forest remain after centuries of exploitation and clearing. In some parts of the country, however, especially in the region of Loudogorie and Strandzha Mountain, it is still possible to find relatively large forested areas with well preserved animal communities, including small mammals.

Although the river banks and valley bottoms have been subject to intensive human activity, some aquatic habitats remain relatively unchanged. Some of these riparian habitats extend over long distances and pass through many landscapes. These habitats are of exceptionally high value as natural corridors for many small mammal species. Of particular interest in this respect are the valleys of the Strouma, Mesta, Maritsa, Tundzha, and Veleka Rivers, as well as some parts of the Danube River bank. The lowland swamp forests along the rivers running into Black Sea sustain very rich small mammal communities. Species that are adapted to humid conditions and characteristic mainly of the mountains in Bulgaria can be found in these lower altitude forests.

The dry, rocky habitats with elements of Mediterranean vegetation that occur in the Strouma River valley in the southwest "corner" of Bulgaria have specific communities of small mammals, including some rare species.

Many habitats of great importance as samples of the most diversified small mammal communities can be found in the mountains. These extensive areas often embrace a wide range of environmental conditions. It is therefore appropriate to regard them as habitat complexes. The most important habitats in these complexes are the high mountain meadows of the Rila, Pirin, Rhodope, Vitosha, and Stara Planina Mountains. Some old and mature coniferous and beech forests in these mountains contain representative samples of the Bulgarian small mammal fauna (Parangalitsa, Boatin, Steneto, etc.).

The valuable habitats mentioned above can be grouped into two regionally and ecologically defined territories of particular importance: (1) territories in the main mountain chains and massifs where most of the Bulgarian small mammal species are represented, and (2) lowland territories where the steppe (Dobrudzha and the northern Black Sea coast) and Mediterranean (the southern Black Sea coast and Strouma and Mesta River valleys near the southern border of the country) small mammal faunal elements can be found.

Sensitivity to Certain Human Activities

The habitats most sensitive to human impact are in the lowlands. These habitats are gradually declining in area and the natural corridors between them are being ruptured. This has become clearly evident during the last twenty years and could become even more severe with the prospect of further economic development. Wetland habitats are among the most fragile. Drainage, land improvement, and agricultural intensification affect dramatically these fragile habitats. The remnants of steppe or forest-steppe grassland in northeast Bulgaria have diminished considerably. Some have been appropriated for urban and agricultural use, others plowed in order to grow grains. Moreover, some steppe areas unsuitable for agriculture have been afforested, which generally reduces their value to steppe wildlife.

The severe conditions of the high mountains make their ecosystems very fragile. Recreation and tourism development of all kinds have caused considerable damage to the habitats in some parts of the Rila, Rhodope, Vitosha, and other mountains.

Taking into account these general considerations, the following species and/or populations are considered very sensitive to the human impact: the populations of all the species included in the Red Data Book; lowland populations of the water shrews (Neomys anomalus and N. fodiens); and species associated with peculiar habitats of pseudo-mediterranean type (Apodemus mystacinus, Suncus etruscus, and Talpa caeca).

Current and Potential Threats

The most important threats to small mammals in Bulgaria include the fragmentation and isolation of their natural habitats as a result of road building, the expansion of tourist and residential development, the modification of the physical environment, and the development of certain more intensive forms of agriculture. The increasing use of pesticides is probably the principal cause of the drastic reductions in the populations of the rare and vulnerable species. However, relatively little information about trends in the populations of rare small mammals or changes in the status of their habitats is available at the regional or national scale.

Sites Containing the Most Representative Samples of Bulgarian Small Mammal Diversity

Species of Economic Importance

Lepus europeus
Orictolagus cuniculus
Microtus arvalis
Nannospalax leucodon

Historic, Contemporary, and Potential Threats to the Survival of the Biota

The climate during the Pleistocene deteriorated gradually. This forced changes in the Pliocene small mammal fauna. Some warm-loving species disappeared, including many insectivores, murids, and glirids. Other species evolved rapidly and adapted to the changing environment. During the Middle Pleistocene, most of the present-day species of small mammals appeared. Parts of southern Europe, where the climatic changes were not very great, served as refugia for some Pliocene taxa. In the region of Thrace, between the Black and Aegean Seas, the climate remained relatively warm and humid. Here Myomimus roachi, a relict of the Pliocene fauna, was able to survive.

The end of the Pleistocene was marked by a considerable "continentalization" of the climate. As a result, the small mammal fauna in Bulgaria came to be dominated by species adapted to open habitats - steppe and forest steppes. Some species that are now rare, or whose current distribution is restricted, were widely distributed over the country during the final phase of the last glaciation (Sicista subtilis, Mesocricetus newtoni, Cricetulus migratorius, Chionomys nivalis). Moreover, the characteristic elements of the Late Pleistocene fauna were steppe inhabitants - Allactaga major, Ochotona pusilla, Lagurus lagurus, Eolagurus luteus - that no longer occur in this part of Europe.

The beginning of the Holocene is characterized by an increasingly humid climate. Consequently, forest vegetation increases. The steppe communities gradually decline in area. Many steppe species decline in numbers and disappear. These changes in environmental conditions, adverse for species adapted to open habitats, caused long-term declines in the populations of Sicista subtilis, Cricetulus migratorius, and Mesocricetus newtoni during the Holocene, and have resulted in their currently restricted distributions.

Increasing human activity caused further deterioration of the environment, leading to continuous losses in most of the main categories of natural habitats. Many habitats have been reduced to a fraction of their former size. It is not only the above mentioned rare species that have been affected; many relatively common species also are experiencing declines in their numbers. In recent decades, additional habitats have been subject to severe pressure from agricultural intensification, tourist development, pollution, urban growth, waste disposal, and other factors. Frequently, the inappropriate planting of new forests damages valuable habitats.

Recommendations

It has recently come to be a widely accepted axiom that species can survive only in appropriate and healthy habitats. Thus, conservation policy that focuses only on individual species is clearly unable to ensure the long-term survival even of the species themselves. Habitat protection must therefore be given far greater priority. For this reason it is important that a broad program of habitat inventory be developed in Bulgaria. On the basis of this information it will no doubt be necessary to enlarge the network of protected areas.

Special attention should be given to the regions along the southern border of the country and Dodrudzha, including the respective parts of the Black Sea coast.

Special studies of the distribution and population ecology of the most threatened small mammal species should be conducted.

It is particularly important that the small mammal communities in the protected areas be studied in terms of fundamental ecological theories. This will contribute to our understanding of the relationships between global and regional environmental gradients on the one hand and the patterns in species assemblages on the other.

Table 1. Legend

Region I: Southern Bulgaria

1. Subregion of Strouma and Mesta Rivers
2. Subregion of eastern Rhodope Mountains
3. Subregion of lower parts of the Maritsa and Tundzha River valleys
4. Subregion of Strandzha Mountain

Region II: Middle Part of Bulgaria

1. Subregion of upper Thracian lowland
2. Subregion of Tundja River lowland
3. Subregion of eastern Balkan Mountain chain
4. Subregion of upper Strouma River valley

Region III: Northern Bulgaria

1. Subregion of Danubian Plain
2. Subregion of Loudogorie
3. Subregion of Dobrudzha
4. Subregion of Predbalkan
5. Subregion of Sofia and Radomir basins

Region IV: Region of the Black Sea Coast

1. Subregion of southern coast
2. Subregion of northern coast

Region V: Region of uplands (above 1000 m)

1. Subregion of Stara Planina (Balkan) Mountain chain
2. Subregion of Rila, Pirin and Rhodope Mountains
3. Subregion of Vitosha-Ichtimanska Sredna Gora Mountains
4. Subregion of Kraischte-Konyavska Mountain
5. Subregion of the western border mountains

Notes:

* = natural areas according to Gruev, 1988
1 = sure occurrence
+ = data that requires further argumentation

Table 1. Occurrence of small mammal species (Insectivora, Lagomorpha, Rodentia) in particular natural areas* of Bulgaria

Species I II III IV V
1 2 3 4 1 2 3 4 1 2 3 4 5 1 2 1 2 3 4
Erinaceus concolor 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1   1 1 1
Talpa europaea 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Talpa caeca                           1          
Sorex araneus +   + + + + 1 1 1 1 + 1 1 + 1 1 1 1 1
S. minutus                 +       +     1 1 1 1
Neomys fodiens 1     1 1 1 1     1   1 1 1   1 1 1  
N. anomalus 1   1 1 1 1 1   1     1 1   1 1 1 1 1
Crocidura leucodon 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
C. suaveolens 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Suncus etruscus                           1          
Oryctolagus cuniculus                           1          
Lepus europaeus 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Sciurus vulgaris 1     1   1 1 1 1 1 1 1 1 1 1 1 1 1 1
Spermophilus citellus 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Dryomis nitedula 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Myomimus roachi   1 1 1                   1          
Glis glis 1 1   1 1 1 1   1 1 1 1 1 1 1 1 1 1 1
Muscardinus avellanarius +     1 1 1 1 1 1 1 1 1 1 1   1 1 1 1
Micromys minutus 1   1 1 1 1 1   1       1 1       1  
Apodemus mystacinus 1               1                   1
A. flavicollis 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
A. sylvaticus 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
A. microps                         1            
A. agrarius 1     1 1 1 1 1 1 1 1 1   1   +      
Rattus rattus 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
R. norvegius 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Mus musculus musculus             1 1 1 1 1 1 1   1 1      
M. m. domesticus 1 1 1 1 1 1               1     1 1 1
M. spicilegus                 1 1 1 1     1        
M. "spretoides" 1 1 1 1 1 1 1 1           1          
Cricetus cricetus                 1 1 1 1              
Mesocricetus newtoni                 1 1 1                
Cricetulus migratorius       1 1 1     1 1                  
Clethrinomys glareolus +         + 1 + +     1 1 +   1 1 1 1
Arvicola terrestris 1     1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Microtus arvalis 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
M. epiroticus 1       1 1 1 1   1     1 1          
M. guentheri     1 1                   1          
M. subterraneus +       + + 1   1       1 1 1 1 1 1 1
Chionomys nivalis   +                         1 1 1    
Sicista subtilis                     1       +        
Nannospalax leucodon 1       1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

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