REVISION OF BANK VOLE CLETHRIONOMYS GLAREOLUS ( SCHREBER , 1780 ) ( MAMMALIA , RODENTIA ) DISTRIBUTION IN SERBIA AND MONTENEGRO

Abstract The present article represents a complete review of all published data (with corrections) on bank vole Clethrionomys glareolus distribution in Serbia and Montenegro. On the other hand, data of 63 unpublished records stored in the period from 1956 to 1983 in the Mammal Study Collection of the Natural History Museum, Belgrade had not been processed until now. In the period from 1992 to 2004, 29 new findings were recorded, 12 of them outside the currently known area of distribution. New data reveal a wider distribution of bank vole than was known until now, completing and partly modifying previous knowledge about this rodent's bionomy and ecology in Serbia and Montenegro. The occurrence of bank vole in the Prokletije Mountains, Kosovo and Metohija, represents its highest known altitude in Europe (2500 m). On the basis of these new data and observations, we can conclude that bank vole is continuosly present in small and linear fragments of autochthonous woodlands on plains and hills, and that there are no large discontinuities in its distribution in Serbia and Montenegro, as was assumed earlier. In efforts to preserve overall biological diversity, the example of the bank vole underlines the need to intensify protection and management of woodlands, especially remaining fragments of forests on plains and in hills.


INTRODUCTION
Bank vole Clethrionomys glareolus (Schreber, 1780) is a typical forest-dwelling rodent species whose distribution encompasses woodlands of the Western Palearctic from France and Scandinavia to Lake Baikal, extends south to Northern Spain and Northern Italy, and includes the Balkan Peninsula (with the exception of most of Greece), Western Turkey, Northern Kazakhstan, and the Altai and Sayan Mountains, encompassing as well Great Britain and the southwestern part of Ireland (Musser and Carleton, 1993).It is distributed throughout Europe, with the exception of marginal areas in the northernmost and southernmost parts of the continent and a number of islands.Discontinuity in distribution, above all in its microcomponents, is caused by the species' exclusive preference for forest habitats (Mitchell-Jones et al. 1999).Such discontinuity was believed to exist in Vojvodina, in the northern part of peri-Pannonian Serbia, and in the main part of Kosovo and Metohija (Petrov,1992).
The optimal habitats of bank vole are deciduous forests of various types, on plains and in moderately high mountains with well developed lower vegetation levels.Less frequently, it is found in mixed and coniferous forests, and in higher mountains.It has been recorded exceptionally rarely above the upper forest limit on high mountain pastures, in rocky habitats, and on talus slopes up to 2400 m of altitude (Viroand Niethammer, 1982;Mitchell-Jones et al. 1999).
The most comprehensive data on bank vole Clethrionomys glareolus distribution and bionomy in Serbia and Montenegro, were presented by Petrov(1992), while data summaries and a brief analysis were published by Savić et al. (1996).Since then, a considerable number of data have been collected that may si-gnificantly complete and modify previous knowledge.The present paper aims to contribute to those efforts.

MATERIAL AND METHODS
The data and maps of Petrov(1992) served as the basis for revision of the distribution of bank vole in Serbia and Montenegro.During the present work, we noticed significant discrepancies of presented data, their UTM coordinates, and their graphic projection on the corresponding maps.Re-mapping was performed on the basis of the presented data, i.e., locality position, which was later evaluated precisely on the map, including affiliation to the corresponding UTM square.This resulted in a modified map of recordings.For record mapping, we used the following four sheets of The Universal Transverse Mercator, Grid Zone 34, Series 1404, Ministry of Defence, UK : 252-C, Zagreb;251-D, Beograd;321-B, Sarajevo;and 322-A, Niš.The map presents data in 10x10 km UTM squares.In the event that a certain square encompassed a set of data, they have been marked cumulatively.Each sort of data has been labeled with a corresponding sign in an effort to gain insight into their distribution.
Previously unpublished data retrieved in the present paper, are given for two periods.They pertain mainly to specimens from the Mammal Study Collection of the Natural History Museum, Belgrade (BEO600.599.1).These specimens were collected from 1956 to 1983 by Dr. Đorđe Mirić1 , Curator of Mammals at that time, and were not cited by Petrov(1992).
In the period from 1992 to 2004 during our permanent field research on mammals in Serbia and Montenegro, specimens were obtained using snap-traps, and barn owl (Tyto alba) pellets were collected at the Mala Moštanica site.Osteological material was extracted in one case from undigested stomach contents of Caspian whip snake Coluber caspius (Mali Jastrebac) and once from red fox (Vulpes vulpes) scats (Mravinjci, Gornji Taor).The collected specimens of bank vole are preserved and stored in the Mammal Study Collection of the Natural History Museum, Belgrade, and at the Institute for Nature Conservation of Serbia, Novi Sad Branch Office, in the form of skins and skulls, as well as skull remains from pellets.In the period from 1998 to 2004, intensified analysis was performed on owl pellets, primarily ones belonging to long-eared owl (Asiootus), barn owl (Tyto alba) and tawny owl ( Strixaluco), in the Siniša Stanković Institute for Biological Research in Belgrade, where bank vole skull remains are stored.In addition to this, all relevant references published after 1992, even though scarce, have been searched.(1992)   The first data indicating a wider distribution of Clethrionomys glareolus in Serbia, outside the presumed areas were presented by Paunović et al. (1996).They recorded four new localities in Vojvodina and the Belgrade district, and stressed the significance of lowland forests and their residues, especially forests along larger rivers such as the Danube, Sava, and Tisa, ones beside swamps, and small forest fragments in hills, as these habitats represent the minimum required conditions for bank vole.Due to the relatively small area and disjunctive disposition of those habitats, the population density of this species is minor.The latest articles that mention Clethrionomys glareolus mainly present results of Asio otus pellet analysis (Kataranovski et al. 1996;Jovanović,2002;Jovanović and Kataranovski, 2002;Jovanović et al. 2003).They report six new localities: in Vojvodina and the Belgrade district, but also on Mt. Maljen. Habijan-Mikešand Štetić (2003) presented data indicating the finding of one specimen in an atypical habitat far from the upper forest limit on Velika Đeravica, Prokletije Mts, Kosovo and Metohija, at 2500 m of altitude, which represents the maximum elevation in Europe.The data mentioned, and unpublished authors' data presented in Table 1 were collected in the period from 1992 to 2004.

DISCUSSION
Through pooling of all available data, the pattern of distribution of Clethrionomys glareolus in Serbia and Montenegro has been completed.A considerable number of new records have been uncovered especially in the Belgrade microregion, Mačva, and several localities in Vojvodina (Southern Srem, Western Banat and Southern Bačka) (Map 1).Although most previously presumed limits and gaps in the range of bank vole seem almost unchanged, new data analysis and the fact that recent investigations were neither aimed at the distribution of bank vole, nor systematically performed indicate that wider presence of this species in Serbia is very probable.
As in the rest of its European range, the presence of Clethrionomys glareolus in Serbia and Montenegro is limited exclusively to forest habitats.According to the authors of previous works (Petrov, 1992), that is the sole reason why the bank vole was not recorded in most of Vojvodina and peri-Pannonian Serbia, where forest habitats are either missing or reduced to spatially and floristically very depleted fragments.The forest associations in which we found bank voles are of various configuration and represent residues of once large autochthonous forests.As for lowland woodlands, we found bank voles in both rarely flooded forests with domination of Quercus robur and Quercus frainetto and periodically flooded forests with domination of Salix alba, Populus nigra, and Alnus glutinosa.It may be assumed that in similar forest habitats (along rivers and channels, on reserves, in forest fragments, etc.) in Vojvodina and peri-Panonnian Serbia, Clethrionomys glareolus has optimal conditions, with disjunction and isolation of the habitat as the basic factors threatening the species and preventing population increase.
In hills bank vole is recorded in small mutually isolated forest reserves with domination of Quercus cerris, Quercus frainetto, and Quercus petraea.The size and PDF created with FinePrint pdfFactory Pro trial version www.pdffactory.comoccurrence of those reserves have a negative trend.The results of our investigation, particularly in such forest patches and residues of lowland forests along rivers and channels (Table 1), confirm records of Mikešand Habijan- Mikeš(1985) indicating that bank vole notwithstanding finds minimum requirements for survival in such habitats.The generally low numbers of bank vole in such forest habitats are frequently registered as "complete absence", and multiple and systematic sampling is therefore essential for its detection.Higher activity of sympatric species such as Apodemus flavicollis and Apodemus sylvaticus (Savić et al. 1976), whose representatives were most often dominant in our samples too, significantly contributes to the rather low number of bank vole recordings.
According to an interesting presumption that we think rather unlikely, bank vole detection in the cited habitats throughout most of the second half of the 20th century was impossible because in the early stages of development or recovery of devastated forest habitats, the minimum required conditions, ensuring its presence did not exist.
New data confirmed earlier records of Petrov (1992) indicating the presence of Clethrionomys glareolus presence in forest habitats of Serbia and Montenegro.Petrov(1992) stated that 67% of the findings were recorded in the immediate vicinity of water bodies of various size and characteristics.This statement is consistent with records in the rest of the European range of the species (Mitchell-Jones et al. 1999).At higher altitudes Clethrionomys glareolus has sometimes been found on talus slopes and in rocky habitats, among stone blocks in forests, or in their close vicinity.Worthy of our attention is the finding of bank vole at Velika Đeravica in the Prokletije Mountains of Kosovo and Metohija, at an exceptionally high altitude (2500 m) far from the upper forest limit in a rocky habitat with large stone blocks (Habijan-Mikešand Štetić,2003).
Analysis of the feeding habits of predators, among them Asio otus, provides a far larger sample.The portion of Clethrionomys glareolus in pellets of A. otus rarely exceeded 1%.This is a result of many factors, principally including the presence of optimal forest habitats, current size of the bank vole population, and the predator's preference for open hunting habitats.In pellets of tawny owl (Strix aluco), which, however, are less numerous than the long-eared owl samples, the percentage of Clethrionomys glareolus prey items exceeded 4%.
According to our data and observations, the bank vole has a continuous distribution in each of the investigated small and linear fragments of autochthonous woodlands of lowlands and hills.We now realise that it has a wider distribution than was previously known.This statement applies to Vojvodina and peri-Panonnian Serbia, especially the main part of Kosovo and Metohija, which were outside the presumed area of distribution.Even though in some parts of this range certain disjunctions are present, they seem to separate microcomponents, i.e., reflect fragmentation of adequate habitats.It is not therefore probable that Clethrionomys glareolus is absent from certain major parts of the territory of Serbia and Montenegro, i.e., the presence of a clear disjunction in distribution area, such as suggested by Petrov(1992), is highly unlikely.Our opinion rather is that more intensive and systematic new field research would prove the existence of a wider and more continuous distribution of bank vole Clethrionomys glareolus in Serbia and Montenegro.
Comparing the abundance of bank vole in Serbia and Montenegro with that of sympatric species at studied new localities during the period 1992-2004, we found that only once did the former exceed the latter.
The once considerable residues of forests have a significant role in survival of Clethrionomys glareolus populations.Protection and conservation of such small and /or linear forest fragments is an important requirement for protection and preservation of bank vole and other forest fauna elements, which would make a notable contribution to maintaining overall biological diversity in Serbia and Montenegro.