• Vadim Sidorovich

Small rodents (mice and voles) species diversity in Naliboki Forest

Updated: Jun 13

Co-authors: Irina Solovej, Ryhor Januta, Anna Sidorovich, Irina Rotenko, Aliaksiej Polazaw, Jeliena Kulikova, Natallia Tsalko, Dmitry Maslaw and Sviatlana Prakof’ieva


In Naliboki Forest there were registered 19 relatively small species of the taxonomic order Rodentia: the bank vole, yellow-necked mouse, birch mouse, wood mouse, striped field mouse, pygmy field mouse, harvest mouse, house mouse, field vole, common vole, root vole, sibling vole, common pine vole, water vole, Norway rat, black rat, forest dormouse, common dormouse and edible dormouse.

In this post we will present the information in relation to the small rodent species in Naliboki Forest as it has been published in the monograph of "Naliboki Forest: Land, Wildlife and Humans" in 2016. The rodent information in the book was published under the same authorship.


We censused small; rodents by means of three methods: snap-trapping and box-trapping to get the species abundance index as well as their total removal from the enclosed plot to estimate the species population density (see Sidorovich, 2011 for the details).




Birch mouse Sicista betulina

The distribution pattern of the birch mouse in the terrain of Naliboki Forest was spotted and the population density was usually relatively lower than those of the majority of the other rodent species. Also, possibly the birch mouse population tended for manifold increasing once per 10-20 years. Sometimes during such an outbreak birch mice predominated even bank voles in population numbers. However, such a situation was registered only once since 1996. Which factors favored to this rodent species to get much higher number was remained unknown, while competition with the bank vole and (or) yellow-necked mouse was probably the reason why the birch mouse was mostly characterized by comparatively lower population density than those of the majority of the other rodent species.


Yellow-necked mouse Apodemus flavicollis

The yellow-necked mouse populated the whole terrain of Naliboki Forest and was common mammalian species there. This rodent species mainly dwelled in forest habitats, but it may be occurred in openings, too.

While snap-trapping in openings of Naliboki Forest, from 0.5 to 2 yellow-necked mice were captured per 100 snap-trap-nights. The population density of the yellow-necked mouse was markedly lower in areas, where surface sand deposits were present, and mostly pine stands with poor forest floor grew. Such situation was recorded, first of all, in the localities of Liakhavyia Hory, Siatryshcha, Rudnia Nalibotskaya, Lysyia Hory, Bliznieta, Biarozawskiya, Siabryn’. In contrast, in the conditions of broad-leaved oldgrowth in the valley of Biarezina river in the downstream of the Patashnia hamlet as well as in other fragments of Naliboki Forest with deciduous broad-leaved oldgrowth (for instance, in the localities of Shubin, Barki, S’miejnaye and Brodnaye the number of yellow-necked mice was rather high. In October 1997 on average 28.1 individuals were caught per 100 snap-trap-nights in broad-leaved oldgrowth in the Drazdy locality, whereas in November 1998 – 7.8 yellow-necked mice per 100 snap trap-nights. However, in the most of forested area in Naliboki Forest the yellow-necked mouse was not so plenty.

Yellow-necked mouse

In autumns of 2004-2013 snap-trapping of small rodents was conducted in Navusts’, Aziarskoye, Kozie Pienna and Valiavatka localities in the typical forest habitats: dry land pine stand, slightly swamped pine forest, spruce-predominated forest and black alder swamp. The abundance index of the yellow-necked mouse as mean-weighted one, taking into account the portions of the above typical forest habitat types, varied from 0.1 individuals per 100 snap-trap-nights in 2005 to 2.5 individuals per 100 snap-trap-nights in 2004.

Estimation of population density of yellow-necked mice by means of their total removal from the enclosed plots in 2003-2007 in localities of Navusts’, Aziarskoye, Kozie Pienna and Valiavatka resulted in as follows: forest habitats, mid summer – on average about 16 individuals per ha; forest habitats, late autumn – on average about 24 individuals per ha; Vol’ka valley without a flood, mid summer – on average about 8 individuals per ha; Vol’ka valley without a flood, late autumn – on average about 3 individuals per ha.


Wood mouse Apodemus sylvaticus

The wood mouse populated the whole terrain of Naliboki Forest and was more or less common mammalian species there. As the yellow-necked mouse this rodent species mainly dwelled in forest habitats too, but at the same time it may be occurred in openings.

While snap-trapping in openings in Naliboki Forest, 0.1-1 wood mice were captured per 100 snap-trap-nights. The population density of the wood mouse was markedly lower in areas, where surface sand deposits were present, and mostly pine stands with poor forest floor grew. Such situation was recorded the localities of Liakhavyia Hory, Siatryshcha, Rudnia Nalibotskaya, Lysyia Hory, Bliznieta, Biarozawskiya, Siabryn’. In the conditions of broad-leaved oldgrowth in the valley of the Biarezina river in the downstream of the Patashnia hamlet as well as in other forested fragments of the terrain with a lot of old deciduous broad-leaved trees (for instance, in the localities of Shubin, Barki, Budy, S’miejnaye, Brodnaye, Kazlow Barok, Klim and Vialiki Hast) the number of wood mice was higher. In October 1997 on average 3.4 individuals were caught per 100 snap-trap-nights in the deciduous broad-leaved oldgrowth in the Drazdy locality, whereas in November 1998 – 5.5 wood mice per 100 snap trap-nights. However, in the most of forested area in Naliboki Forest the wood mouse was rarer.

In autumn 2004-2013 snap-trapping of small rodents was conducted in Navusts’, Aziarskoye, Kozie Pienna and Valiavatka localities in the typical forest habitats: dry land pine stand, slightly swamped pine forest, spruce-predominated forest and black alder swamp. The abundance index of the wood mouse as mean-weighted one, taking into account the portions of the above typical forest habitat types, varied from 0.1 individuals per 100 snap-trap-nights in 2005 to 0.6 individuals per 100 snap-trap-nights in 2010.

Among the above-mentioned commonly presented forest habitats wood mice were more frequently captured in fairly old spruce-predominated forest with well-developed underbrush and rich forest floor – 0.4-14.7, mean 3.3 individuals were caught per 100 snap-trap-nights.

Estimation of population density of wood mice by means of their total removal from the enclosed plots in 2003-2007 in the localities of Navusts’, Aziarskoye, Kozie Pienna and Valiavatka resulted in as follows: forest habitats, mid summer – on average about 4 individuals per ha; forest habitats, late autumn – on average about 15 individuals per ha; Vol’ka valley without a flood, mid summer – on average about 6 individuals per ha; Vol’ka valley without a flood, late autumn – on average about 6 individuals per ha.


Striped field mouse Apodemus agrarius

In Naliboki Forest the striped field mouse mainly populated openings of both types: dry land meadows that situated on glades and drained marshes; and undisturbed grassy marshes. The species was even able to inhabit inundated reed marshes, where in the core areas only this rodent species was registered, perhaps, with merely exception of few cases, when feeding places of water voles were recorded there.


Striped field mouse

Estimation of population density of the striped field mice by means of their total removal from the enclosed plots in 2003-2007 in the localities of Navusts’, Aziarskoye, Kozie Pienna and Valiavatka resulted in as follows: forest habitats, mid summer – less than one individual per ha; forest habitats, late autumn – less than one individual per ha; the Vol’ka river valley without a flood, mid summer – about 2 individuals per ha; the Vol’ka river valley without a flood, late autumn – about 3 individuals per ha; the Navusts’ glade, mid summer – about 3 individuals per ha; the Navusts’ glade, late autumn – about 4 individuals per ha. Taking into account snap-trapping bag in the localities of Navusts’, Stas’kava and Pawnochnaye Wiunishcha, population density of the striped field mouse was twice higher in dry meadow on the drained lands than that on the Navusts’ and other glades. Concerning the between-year changes in number of the striped field mouse, merely the data on snap-trapping of small rodents on the Navusts’ glade in autumn of 2004-2011 are available, which show 11 fold of maximal difference in the abundance index of the species and presence of one population peak during these eight years.


Pygmy field mouse Apodemus uralensis (microps)

There is a little evidence in relation to presence of this rodent species in Naliboki Forest. During long-term trapping of rodents in 1997-2011, whicht was aimed to reveal their species diversity, distribution patterns, activity, population densities and trends in Naliboki Forest, the pygmy field mouse was captured three times and in Aziarskoye locality only. Two individuals were caught in boggy pine forest, while the third individual was found in dry-land pine forest with floor prevailed by berry-shrub. In order to realize trapping efforts done during the fourteen years, it is noteworthy to get know that more than 44 thousands trap-nights were fulfilled and more than 5 thousands rodent individuals were caught. The trapping sessions were mainly conducted in the localities of Navusts’, Aziarskoye, Kozie Pienna, Valiavatka, Zabalats’, Stas’kava, Drazdy, Pawnochnaye Wiunishcha, Budy, Sukhi Barok and Koniki. Thus, the above data evidence that in Naliboki Forest the pygmy field mouse lived locally and with a low population number. Perhaps, this rodent species mostly inhabited ecologically poor pine forests.


Harvest mouse Micromys minutus

Harvest mouse

The harvest mouse was common species of small rodents in open places mostly, where there were dense and tall grass with bushes. Conversely, in the sand dune habitats with pine stands the species lived quite rarely or was absent in the majority of places. Favourable environmental conditions for the harvest mouse took place in open valleys of rivers, along canal banksides, on forest glades, meadows on drained lands (particularly at forest edges), at open marsh edges or in dense bushes inside this habitat type etc. Fairly large habitats having rather high carrying capacity for the species were found in the Vol’ka and Islach river valleys, upper part of the Kamienka river valley, most of open places in the Biarezina and Nioman valleys as well as in all numerous mostly open places on abandoned drained lands, for instance, in the localities of Kupalishcha, Masty, Hala Balota or Symonava. In late summer and early autumn population density of the harvest mouse in such favourable habitats was up to 186, on average 62 individuals per hectar.


House mouse Mus musculus

In Naliboki Forest the house mouse populated human settlements and their nearest surroundings outside of forest habitats. In wild terrain the species was nearly absent.


Bank vole Myodes glareolus

The bank vole was the most common species of rodents and all other mammals in Naliboki Forest. This feature was more pronounced in forest habitats. Only in open grassland (marshes and dry land meadows) the bank vole was lower in numbers than Microtus voles alltogether in the years of population outbreak. In the whole (i.e. in the mean-weighted values) according to the data that were gained in 2004-2010 in the Navusts’ surroundings the portion of bank voles in rodent community constituted from 68.0 to 89.7% and averaged 82.4%.

The population density of the bank vole was markedly lower in areas with surface sand deposits and pine stands with poor forest floor. Such situation was recorded in the localities of Liakhavyia Hory, Siatryshcha, Rudnia Nalibotskaya, Lysyia Hory, Bliznieta, Biarozawskiya, Siabryn’. In contrast, in the conditions of broad-leaved oldgrowth in the valley of Biarezina river in the downstream of the Patashnia hamlet as well as in other fragments of Naliboki Forest with deciduous broad-leaved oldgrowth (for instance, in the localities of Shubin, Barki, S’miejnaye and Brodnaye the number of bank voles was rather high.

Bank vole

Direct assessment of bank vole population density in July-October of 2003-2007 by entire capturing in an enclosure in the localities of Navusts’, Aziarskoye, Kozie Pienna and Valiavatka resulted in as follows: forest habitats, mid summer – on average about 70 individuals per ha; forest habitats, late autumn – on average about 134 individuals per ha; the Vol’ka river valley without a flood, mid summer – on average about 48 individuals per ha; the Vol’ka river valley without a flood, late autumn – on average about 117 individuals per ha. In order to reveal the between-year changes in the population density of the bank vole in Naliboki Forest, in the autumns of 2004-2013 snap-trapping of small rodents was conducted in the Navusts’, Aziarskoye, Kozie Pienna and Valiavatka localities in the typical forest habitats: dry land pine stand, slightly swamped pine forest, spruce-predominated forest and black alder swamp. It was found that the mean-weighted abundance index of the bank vole ranged 9.2 fold during the period of the study.


Common vole Microtus arvalis

Common vole

In Naliboki Forest the common vole was seemingly the commonest species among Microtus voles. So as the species population cycles (as the other Microtus vole species populations), the common voles densely populated dry-land or slightly swamped meadows in the years of the species population outbreak only. The common voles occurred in grassy marshes too, particularly along their edges. In forest habitats the common vole was rare species all the time and it sometimes occurred there nearby ecotones with openings. Direct assessment of common vole population density in July-October of 2003-2007 by entire capturing in an enclosure in the localities of Navusts’, Aziarskoye, Kozie Pienna and Valiavatka resulted in as follows: forest habitats, mid summer – no individuals captured; forest habitats, late autumn – on average about 2 individuals per ha; the Vol’ka river valley without a flood, mid summer – on average about 90 individuals per ha; the Vol’ka river valley without a flood, late autumn – on average about 158 individuals per ha. Actually the above-given values relate to both species the common vole and sibling vole, because the latter could not be morphologically distinguished from the common vole.


Sibling vole Microtus subarvalis

In order to reveal presence of this rodent species, which is morphologically almost the same with the common vole, in autumn 1998 twenty individuals seemed to be common voles from Pawnochnaye Wiunishcha locality and ten such individuals from Hala Balota locality were genetically examined. Only three individuals from Hala Balota locality were identified as the sibling vole. Nothig more is available to get know about the species, nevertheless, undoubtedly that the sibling vole populated grassy openings in Naliboki Forest and it was not rare.


Field vole Microtus agrestis

Field vole

In Naliboki Forest the field vole was common species of rodents in grassy openings (meadows and marshes), but only in the years of the species population outbreak (the species is characterized by a cycling population dynamics). In forest habitats the field vole was rare species all the time, but it sometimes occurred there nearby ecotones with openings.

Direct assessment of field vole population density in July-October of 2003-2007 by entire capturing in an enclosure in the localities of Navusts’, Aziarskoye, Kozie Pienna and Valiavatka resulted in as follows: forest habitats, mid summer – no individuals captured; forest habitats, late autumn – on average about one individual per ha; the Vol’ka river valley without a flood, mid summer – on average about 47 individuals per ha; the Vol’ka river valley without a flood, late autumn – on average about 89 individuals per ha.


Common pine vole Microtus subterraneus

In Naliboki Forest the common pine vole was more or less common mammalian species, but it was not so common as either the common vole or field vole or even the root vole. There the common pine vole mostly lived on grassy opennings, but also it occurred in forest habitats, especially in broad-leaved oldgrowth, for instance, in the Biarezina river valley. There in October 1997 on average 0.9 individuals were caught per 100 snap-trap-nights in broad-leaved oldgrowth in the Drazdy locality, whereas in November 1998 – 2.4 individuals per 100 snap trap-nights. At the same time in November 1998 on the neibouring glade six common pine voles were caught per 75 snap-trap-nights (i.e. 8 individuals per 100 snap trap-nights).

Estimation of the common pine vole population density in July-October of 2003-2007 by entire capturing in an enclosure in the localities of Navusts’, Aziarskoye, Kozie Pienna and Valiavatka resulted in as follows: forest habitats, mid summer – sporadically few individuals; forest habitats, late autumn – sporadically few individuals; the Vol’ka river valley without a flood, mid summer – on average about 14 individuals per ha; the Vol’ka river valley without a flood, late autumn – on average about 33 individuals per ha.


Root vole Microtus oeconomus

The root vole may be occurred in Naliboki Forest in all localities. The species population cycled as well as the populations of the other Microtus vole species. The root vole mostly inhabited meadows and especially grassy marshes, where its population density was markedly higher. Concerning spatial distribution, in meadows root voles lived more evenly, whereas in floodplain marshes they stayed patchy (in one place there were many root voles, while on the distance of one km in the upstream or downstream there was no any root vole found). Root voles occurred in forest habitats too, especially in broad-leaved oldgrowth, for instance, in the valley of Biarezina river. There in October 1997 on average 0.7 individuals were caught per 100 snap-trap-nights in broad-leaved oldgrowth in the Drazdy locality, whereas in November 1998 – 2.3 individuals per 100 snap trap-nights.

Root vole

Estimation of the root vole population density in July-October of 2003-2007 in the localities of Navusts’, Aziarskoye, Kozie Pienna and Valiavatka resulted in as follows: forest habitats, mid summer – sporadically few individuals; forest habitats, late autumn – sporadically few individuals; the Vol’ka river valley without a flood, mid summer – on average about 37 individuals per ha; the Vol’ka river valley without a flood, late autumn – on average about 65 individuals per ha.



Water vole Arvicola terrestris

According to the words of locals and several workers, who drained swamps in Naliboki Forest, there in 1950s-1970s the water vole was common species in this initially heavily swamped terrain. Its population seemed to be quite stable and there was no any temporal disappearance of this noticeable species before. At present in Naliboki Forest in one place there is no the species, in others the water vole is not so common as it used to be despite of rather favourable habitats for the species are still fairly wide-spread there even after the draining of the terrain.

It is worthwhile to notice that the habitats in Naliboki Forest were much improved by the terrain-wide unundations by beavers created the dense population there to the late 2000s. At that time beavers inhabited Naliboki Forest with the population density of 1 to 8 or 3-4 settlements per one square km on the average. On the whole, in the 2000s and early 2010s there were about 5-7 thousand beaver settlements and about 4 thousands beaver ponds, which were full of water. Additionally, there were 2-3 thousand pond remains in the abandoned settlements of beavers. In effect, in all the localities much favourable habitats of the water vole appeared Nevertheless, there was not registered any marked increase in water voles afterwards.

Water vole

In 1997-2000 and 2004-2005 in Naliboki Forest the local population of the water vole was quite extensively examined and the studies showed spotty spatial structure. Such population patches were distributed irregularly at distance 2-5 km apart; and habitats with high density of water voles occupied areas of not more than one (mean about 0.2) square km. In such population fragment in pre-reproductive period the number of individuals was approximately from 10 to 120, whereas in autumn after reproduction their numbers were 4-10 fold higher. While take into account pregnant females and young individuals captured, breeding in water voles in Naliboki Forest took place two or three times per year in the period from late April till mid September.

The terrain-wide registrations of water vole latrines on itineraries that were fulfilled in 1997-2000 gave the following results. The high number of water voles was registered in the Zabalats’ locality in the summer 1998; Kupalishcha – summer 1999; S’miejna – summers 1998, 1999; 2000; low or very low number of water voles – Zabalats’, summer 2000; Shubin – summer 1998; medium numbers of this prey – Hala Balota, summers 1999 and 2000. At the same time in the large valleys of Biarezina and Nioman with numerous floodplain lakes the water voles were nearly not found. Also, it should be noticed that during the studies in 1997-2000 many localities, which undoubtedly favoured the water voles, were not inspected.


Young water vole.


In the period of 2001-2014 doing either a special study on water voles (2004-2005) or studies on other species in Naliboki Forest, we faced with much quite irregular changes in water voles. In other words, there was not registered a plausible continuous trend of recovering in the water vole population that connected with the secondary swamping due to damming by beavers. Nevertheless, there were short-term increases in water vole number and respective enlargering of the species distributions in 2004-2005, 2009-2010 and in 2014-2015. In other years the water vole number and distribution decreased to the fairly low level similar to that in 1999.

By summarizing all the information gained in 2001-2015, the following may be concluded. In 2001-2011, the local population of the water vole persisted almost the terrain-wide still (with exception of a part of north-eastern localities), but having patchy distribution with higher or lower number of such population fragments that, in turn, have higher or lower number of individuals in the between-year changes. In 2004-2005 and 2009-2010 i.e. after the population crashes in American minks happened in autumns of 2003 and 2008, respectively, the water vole population grew in distribution and density. In 2012-2013, perhaps, the decline in water voles was exacerbated somehow, and the species got even considerably less commom in Naliboki Forest. Plausibly, the species survived only in 10-20 local places within the swamped areas stretched along the Nioman and Biarezina river valleys, but at the same it was rare inside the valleys themselves. In 2012-2013 in the north-eastern half of the terrain the water vole seemingly disappeared entirely. However, in the autumn of 2014 and the spring of 2015, quite on contrary, the water vole appeared in numbers in the several localities, where it was nearly absent for long-term, e.g. the Navusts’ and Stas’kava, or the species number suddenly increased in the localities of its permanent presence, but mostly with a low population density e.g. Barsucha, Yunitsa and Sukhi Barok.

In 2001-2015 the main findings (not all of them) of the species presence in Naliboki Forest were as follows: abandoned peatery and drainage canals in the localities of Sviaty Kalodziezh, Khmielishcha and Dzieraminishcha – 2004, 2005, 2007 and 2010; the Islach river valley at its confluence with the Valozhynka river – 2005, 2010 and 2011; the Vol’ka valley in the river downstream from the Valiavatka locality – 2005; the locality of Yunitsa – 2005 and 2011; the Masty and Kupalishcha former peatories – 2005, 2009 and 2010; the Hala Balota former peatery and drainage canals – 2002, 2004, 2005 and 2008-2011; abandoned drained lands in the Symonava locality – 2008-2011; the former valley of the Vusa river in the localities of S’miejnaye and Brodnaye – 2005, 2010 and 2011; abandoned drained land in Valasien’ locality – 2005, 2011-2014; the Biarezina river valley at Al’shanka mouth – 2005, 2010, the Niarovy locality – 2005, 2014; Stas’kava, Navusts’, Barsucha, Yunitsa and Sukhi Barok – 2014, 2015. Futhermore, even among these findings there was not anyone, when thousands of water voles populated a particular area. At its best there were approximately 600-800 individuals in early autumn, whereas until mid-spring about one hundred or even fewer individuals survived. This evidenced about vulnerability of such population fragments to possible strong predation impact by many rodent eaters.

Also, it is worthwhile to mention one outstanding finding of the water vole presence. In 2012-2015 in the Navusts’ hamlet we found a fairly isolated local group of water voles. They inhabited yards of five houses and as far as we learn they mostly fed on the yard grass that was cut regularly. In winter under snow cover the cut grass was green for the majority of shoots. Perhaps, all the time presence of young grass shoots attracted the water voles. Interestingly, that in the neighbouring valley of the Vol’ka river the species was almost not found until the autumn 2014.


Norway rat Rattus norvegicus

In Naliboki Forest the Norway rat densely populated human settlements and their surroundings and particularly banks of streams running there. The Norway rats rarely stayed in wild terrain of Naliboki Forest, but always it was not too faraway from human settlements (usually not further than one km). Sometimes the Norway rat was found quite faraway what is likely to explain by the species ranging along watercourses. In summer the Norway rats may replace from village to drainage canals in its surroundings and even quite faraway (up to 4 km). Such situation was regularly registered in Kliatsishcha village that is situated in the middle of Naliboki Forest close to numerous canals. The Norway rats walked fairly often by forest roads from one human settlement to another.


Black rat Rattus rattus

There a little data about the black rat presence in the terrain of Naliboki Forest as well as in the whole Belarus. One of the true information, perhaps, about the black rat it was the black-coloured rat carcass (it was killed by the red fox and refused afterwards) in late autumn of 1989 at the forest edge close to Pialiuzhyna hamlet.

There were several recent findings of black rat in Naliboki Forest: in November 2019 in the budy locality and in March 2020 in the Brodnaje locality.


Forest dormouse Dryomys nitedula

There are not much reliable information about presence and distribution of the forest dormouse in Naliboki Forest. The species was either snap-trapped or its skull was found in an owl pellet in the following localities: Drazdy, Chuhurka, Patashnia, Karaliova, Piatukhova, S’miejnaye, Budy, Barki, Lipovitsa, Shubin, Halajbova Grada and Krasnaya Horka. The locations suggest that in Naliboki Forest the species prefers broad-leaved oldgrowth with oaks and lindens as well as mature spruce-dominated forests with fairly rich underwood.


Common dormouse Muscardinus avellanarius

There are not much reliable information about presence and distribution of the common dormouse in Naliboki Forest. The species was either snap-trapped or its skull was found in an owl pellet ot it was found in an aftificial bird nest-box etc. in the few following localities only: Chuhurka, Karaliova, Krupli, Valasien’, Brodnaye and Halajbova Hrada.


Fat dormouse Glis glis

In Naliboki Forest the fat dormouse was only once registered in the surroundings of the Paniamon’ hamlet by zoologist Lieanid Shkliarow in 1985. Also, in June 2017 we observed fat dormouse in broadleaved deciduous oldgrowth in the Votchyn locality nearby the Brodnaje hamlet.

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