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The dynamics of socio-spatial organisation are little investigated in dormice (Gliridae), a specific group among small mammals. During 2007–2017, 668 adult individuals were captured in a hazel dormouse (Muscardinus avellanarius) population in Lithuania, with the home ranges calculated for 134 males and 62 females. Over the study period, the abundance of the population gradually declined, and it was categorised into three groups: (1) high (1.2–1.4 adults/ha), (2) medium (0.9–1.0 adults/ha) and (3) low (0.4–0.7 adults/ha). When population abundance changed from high to low, the average sizes of home ranges increased from 1.4 ± 0.6 to 2.1 ± 1.2 ha in males and from 0.8 ± 0.5 to 1.1 ± 0.4 ha in females, while the total overlap of home ranges decreased from 57 ± 28 to 35 ± 23% in males and from 77 ± 27 to 44 ± 32% in females. Home ranges of marked individuals changed in consecutive years. In males, the average displacement of the centres of the home ranges was 58 ± 21 m, 75 ± 52 m and 73 ± 39 m at high, medium and low densities, respectively. The dynamics of the spatial relations in the investigated hazel dormouse population are consistent with the general tendency of home ranges to increase when population density decreases. However, the spatial organisation of population is more stable and potentially less related to the dynamics of food resources in comparison with other forest-dwelling small mammals.

Lithuania is situated in the north-western corner of the large distributional range of the herb field mouse, Apodemus uralensis. Apodemus uralensisis distributed mainly in the north-western part of Lithuania, where the majority of specimens were captured in the ecotones of mixed forests and open habitats (natural meadows, cornfields and fallow fields) and in open habitats bordering forests or situated close to them. Apodemus uralensisis rare in Lithuania: the average relative abundance was only 2.2 ind. per 100 trap-days and it accounted for up to 8.5% of all small mammals trapped. Avoidance of forest habitats and preference of ecotonic habitats, as well as the comparatively low abundance, are the main peculiarities of A. uralensisin the north-western corner of the range.

Lithuania is situated in the north-western corner of the large distributional range of the herb field mouse, Apodemus uralensis. Apodemus uralensisis distributed mainly in the north-western part of Lithuania, where the majority of specimens were captured in the ecotones of mixed forests and open habitats (natural meadows, cornfields and fallow fields) and in open habitats bordering forests or situated ciose to them. Apodemus uralensisis rare in Lithuania: the average relative abundance was only 2.2 ind. per 100 trap-days and it accounted for up to 8.5% of all small mammals trapped. Avoidance of forest habitats and preference of ecotonic habitats, as well as the comparatively low abundance, are the main peculiarities of A. uralensisin the north-western corner of the range.

We investigated the influence of a colony of great cormorants on the skull morphometry of yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) of three age groups trapped in the territory of the colony in 2011- 2014. In general, most of the skull differences in both species were related to character length (skulls tended to become longer). In A. flavicollis, the skull size differences between zones were most expressed in subadult and adult individuals, while in M. glareolus they were most expressed in juveniles, with only a few characters different in adults and none in subadult voles. For both species, the largest skull characters were found mostly in the zone characterized by both the greatest number of cormorant nests and the longest and strongest influence by the colony. Concluding we confirm that the great cormorant colony has an influence on the skull morphometry of A. flavicollis and M. glareolus and we hypothesize that these differences enhance the ability of survival in specific conditions.

In 2012–2014, seven species of small mammals were trapped indoor in East and Central Lithuania, Mus musculus,and Apodemus flavicollisdominating. Population sex and age structure, reproductive aspects, body condition, and morphometry of these species are analyzed in this paper. In the dominant species, the sex ratio did not differed from 1:1. Indoor breeding was analyzed in M. musculus(average litter size 5.9 ± 0.6, min. 2, max. 13 juveniles) and A. flavicollis(3.7 ± 0.7, 2–6 juveniles). No significant influence of the month on litter size was found in M. musculus, winter breeding was registered. Average body condition index of indoor-trapped A. flavicolliswas C = 3.17 ± 0.11, while that of M. musculuswas C = 3.39 ± 0.05. The body condition index of M. musculusdid not depend on gender, animal age, or month of trapping, that is it was very stable. The role of commensal small mammals in the circulation of human pathogens is discussed.

We investigated the influence of a colony of great cormorants on the skull morphometry of yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) of three age groups trapped in the territory of the colony in 2011–2014. In general, most of the skull differences in both species were related to character length (skulls tended to become longer). In A. flavicollis, the skull size differences between zones were most expressed in subadult and adult individuals, while in M. glareolusthey were most expressed in juveniles, with only a few characters different in adults and none in subadult voles. For both species, the largest skull characters were found mostly in the zone characterized by both the greatest number of cormorant nests and the longest and strongest influence by the colony. Concluding we confirm that the great cormorant colony has an influence on the skull morphometry of A. flavicollisand M. glareolusand we hypothesize that these differences enhance the ability of survival in specific conditions.

In the summer of 1989, a single adult male root vole (Microtus oeconomus) was trapped in the meadow at Kovališki, Latvia. It was registered in the site, characterised by low small mammal diversity (nine species, Shannon’s H = 0.97). Among three sampled habitats in the Kovališki site, meadow had most diverse small mammal composition, while forest and swamp were characterised by three species each in the period of 1984–1990. This is the first record of M. oeconomusfor Latvia, thereby also expanding the known distribution range. This finding is very much in line with the north and eastward spread of the species in Lithuania, an expansion that started in the Nemunas Delta and, at least partly, tied to land abandonment in the years since the 1990s creating suitable habitat for M. oeconomus. Its distribution in Baltic countries is still however limited to Lithuania and, possibly, closely adjacent areas in Latvia. Old records of M. oeconomusfrom Estonia were not confirmed in the last decades.

Owl pellets have high potential as a source of DNA. However, this noninvasive method of collecting DNA is rarely used, and its methodological aspects are poorly understood. We investigated the methodology for DNA extraction and amplification from owl pellets containing the smallest European rodent—the Harvest mouse Micromys minutus—as an example. We used mandibles identified in owl pellets for mitochondrial and nuclear DNA amplification. For DNA extraction, we tested two commercial protocols and utilized a protocol being a combination of two commercial kits which ensured high efficiency of DNA extraction. Additionally, we recorded that the amount of DNA was five times higher in extracts from teeth as compared to DNA extracts from jawbones derived from the same mandible. The quantity of DNA was significantly positively correlated with biological sample weight; however, the age of the pellet remains had an impact on the level of inhibition. We recorded inhibition in 40 % of mtDNA extracts derived from pellets older than 150 months, whereas in DNA extracts from pellets younger than 80 months, we did not observe a negative impact of inhibition on PCR efficiency. The amplification success rate was 89.9 % for the mitochondrial fragment and 39.4 % in the case of the nuclear fragment. We observed partial degradation of DNA evidenced by the fact that the longest fragments that we were able to amplify in the case of mtDNA were 450 and 200 bp for nuDNA. The study shows that pellets can be considered as a source of DNA and have high potential for molecular research in the case of threatened species and species that are difficult to study using standard field techniques.

Vegetation parameters determining nest site selection by the hazel dormouse Muscardinus avellanariuswere studied in a typical habitat where dormice are relatively common in Lithuania, the northern periphery of its distributional range. Dormice preferred nest sites with a better-developed understory, particularly with a good cover of hazel shrubs taller than 4 m and plentiful bird cherry trees, a high diversity of woody plant species in the understory and overstory, and better connectivity of the nest tree with its surroundings. They avoided sites with a high number of mature Norway spruce trees in the canopy and a high density of young trees. In a stepwise multiple regression analysis, three vegetation parameters of the number of shrub species, the cover of hazel shrubs, and the number of Norway spruce trees in the canopy determined over 85% of the index of nestbox use by M. avellanarius. The number of shrub species in the surroundings of the nest site had the highest impact of all. Nest sites used by dormice for breeding were distinguished by a better-developed understory, particularly by a significantly higher number of bird cherry trees and a lower number of Norway spruce trees in the canopy, as well as a higher diversity of plants in the understory and overstory. Selection of nest sites by M. avellanariusis a combination of safety from predators and the presence of food. A well-developed inter-connected understory ensures the safety of nest sites from predators, and the diversity of understory and overstory species guarantees continuity of the food supply in the vicinity of nest sites.

The influence of the annual spring floods on small mammal communities was studied in the Nemunas River Delta, SW Lithuania. The aim of the investigation was to compare the diversity of small mammals inhabiting spring-flooded meadows, meadows not subjected to flooding and spring-flooded forest in years characterized by differing heights and durations of spring flood. In the years of the high flood, the number of species and diversity index were higher, while index of dominance was less than in the years of low flood. Significantly, the highest proportions of Apodemus agrarius were recorded in spring-flooded meadows in years of high flood (41.7%), while Microtus oeconomus occurred in the highest proportions in spring-flooded meadows in years of low flood (66.8%) and in meadows not subjected to flooding (47.1%). In non-flooded areas, M. Oeconomus is not expelled by the floods and outcompetes other species. After high levels of flooding, during the process of re-population, the voles may be outcompeted by A. agrarius. In the absence of dominant species, greater opportunities existed for the establishment of more species (13 species in flooded meadows). Micromys minutus accounted for up to 19.5–30.1% in the years of high flood. We concluded that the annual spring floods in the Nemunas Delta had no long-term negative effects, the number of small mammal species and their abundance had been restored in just a few months. The worst consequences of the high flood were recorded in forest habitat. Spring floods, and especially the higher floods, are natural environmental agents, maintaining the high diversity of small mammals in meadows and reed-beds.

The trapping of small mammals in eight natural or semi-natural habitats in 2008–2010 yielded 13 species, three of which (root vole, pygmy field mouse and northern birch mouse) were registered in the territory of the Žagarė Regional Park for the first time. Striped field mouse dominated in natural meadows (32.9% of all trapped individuals), yellow-necked mouse in re-growing clearcuts, shrubby meadows and abandoned farmsteads (18.2%, 32% and 67.5%, respectively), and bank vole in forest meadows, forest wetlands, planted young forests and mixed forests (30.7%, 43.9%, 51.1% and 60.5%, respectively). The diversity of small mammals was significantly lower in forest habitats (compared by diversity ordering using Rényi index family) than in open areas. Compared to investigation done in 1975, species numbers and diversity in 2008–2010 were significantly higher (10 vs. 13 species, and Shannon’s H = 1.67 vs. 2.59, respectively), while relative abundance was lower (25.4 ± 2.12 vs. 56.1 ± 8.03 individuals per 100 trap/nights).

In the article, data about concentrations of heavy metals (Cu, Cr, Ni, Pb, and Cd) in bodies and stomach contents of bank voles (Clethrionomys glareolus) from seven protected and agricultural territories are presented. In both the bodies and stomach contents of the voles the highest accumulated heavy metal levels were those of Cu, with an exception of three cases: in the spring of 1998, when in the stomach contents from agricultural territories of Eastern and Western Lithuania the concentration of Ni was the highest, and in the autumn of 1999, when in the bodies from the deltaic plain of Western Lithuania the concentration of Pb was the highest. Concentrations of individual heavy metals in the bodies and stomach contents differed within a wide range. The levels of Cd usually were the lowest. In spring and autumn, in the voles from protected territories total concentrations of heavy metals fluctuated between 25.2 and 6.0 and in their stomach contents – 3.7 and 4.1 times, respectively. In the animals from agricultural territories they varied from 11.1 to 20.7 in bodies and – from 2.0 to 4.4 times, in their stomach contents. In the bodies of both adult and young voles, in comparison with the stomach contents, concentrations of all the heavy metals usually were lower. As a rule, higher total heavy metal concentrations in the stomach contents were related to higher total heavy metal concentrations in the bodies (r = 0.767).

Six house mice (Mus musculus), seven yellow-necked mice (Apodemus flavicollis), 10 striped field mice (A. agrarius), five muskrats (Ondatra zibethicus), one water vole (Arvicola terrestris), 126 bank voles (Clethrionomys glareolus), 12 short-tailed voles (Microtus agrestis), and two European beavers (Castor fiber) were examined for helminths. Data are presented about infection of the rodents with trematodes, nematodes, and larvae of cestodes. Twenty three helminth species were found. In Lithuania, Echinococcus multiloculariswas found in rodents for the first time. Three helminths were found in new hosts in Lithuania: Plagiorchis elegans– in the bank vole, Mastophorus muris– in the house mouse, and Tetratirotaenia polyacantha– in the muskrat. In the European beaver, only Stichorchis subtriquetrusand Travassosius rufus, helminths specific to this species, were detected. The helminth fauna in the muskrat and the water vole was formed of helminths hosted by a wide range of waterfowl and mammals.

All 560 individuals of small rodents belonging to six species of the families Cricetidae and Muridae were trapped in different habitats of various districts in Lithuania in 1995–2001. To determine Frenkeliainfection, brain samples were examined. Cysts of Frenkeliawere detected in the brain of three vole species only. The average rate of infection in bank voles (Clethrionomys glareolus) was 21.1%. With different localities the prevalence of Frenkeliainfection varied significantly (from 0.0% to 60.6%). Only one out of 35 root vole (Microtus oeconomus) and one out of 24 short-tailed vole (M. agrestis) individuals contained cysts. There were two Frenkeliaspecies established in voles: F. glareoliin C. glareolusand F. microtiin M. oeconomusand M. agrestis. All the 23 examined common vole (M. arvalis), 31 striped field mouse (Apodemus agrarius) and 106 yellow-necked mouse (A. flavicollis) individuals were uninfected. These results turn to be the first contribution to the investigation of the Frenkeliafauna, its prevalence and distribution among certain mouselike rodent species in the Baltic States.

AbstractShort summary of the results of investigations in Radviliškis, Telšiai and Šalčininkai districts is given in this paper, covering territorial aspects, species composition and communities, measures needed for further protection.

AbstractThe DBMS software, currently being used for the Biodiversity database management, developed by the project group “Ecological diversity of Lithuania” and currently maintained at the Institute of Ecology (Vilnius, Lithuania), is Borland® Paradox®, mainly Paradox® for DOS ver. 4.5. The relational structure of the database contains minimum of coding and allows to perform data management and all basic outputs, using forms and reports of the standard interface, it does not require special programs or applications in DBMS environment. The database contains a taxonomic and literature citation blocks, species distribution data files (Budrys, 1998, in press). Particular data block of the database contains lists of geographic names, and habitat information. These files are linked to a master file with records related to 1×1 km grid of territory, designed as a raster database. For particular purposes of inexperienced user, a minimized regional version of the database (RBIDB) with a user-friendly interface was created, compatible with the Biodiversity database. It allows to manage data on the local faunistic lists of species, distribution of species in the region, phenological data, abundance of species in particular localities and territories, digitized boundaries of protected and other important territories, and additional textual information on species, localities and territories.

AbstractSummary of small mammal trapping data in Lithuania is given in the first article of a series. Results are reviewed from the point of view of trapping effort, character of investigation and the interdependencies of community indexes. Consideration about the threshold of trapping effort is presented along with practical implications on the correct use of community indexes.