| Abstract [eng] |
There are lots of investigations of small mammal communities not only in Lithuania, but in other countries as well. But that is to say, majority of these researches are made in vegetative season of the year and winter data on small mammal communities are lacking. The aim of this investigation was to investigate seasonal changes in small mammal community in non – vegetative season in Zarasai district. Objectives of the research were to analyze published data of similar research from Lithuania and other countries as well, snap-trap and examine small mammals from study area in non-vegetative season, evaluate the abundance of small mammal populations, frequency of detection, the composition of age and sex, to estimate changes in small mammal community structure using Shannon-Wiener diversity index (H) and Simpson’s dominance index (c), to analyse the influence of snow cover depth and air temperature on small mammals abundance and to investigate, whether mandibular and maxillary measurements in shrews, mise and voles differ between winter and non-winter periods. In current investigation small mammals were snap-trapped all winter season (from October to the end of April) of 2004–2005 and 2005 – 2006 in the East Lithuania, Zarasai district, near lake Ilgelis, in the former farmstead territories. Total number of the trap-days in 13 (2004/05) and 19 (2005/06) trapping sessions was 3295 and 427 individuals of nine small mammal species were trapped: common shrew (Sorex araneus), pygmy shrew (Sorex minutus), house mouse (Mus musculus), yellow – necked mouse (Apodemus flavicollis), pygmy field mouse (A. uralensis), striped field mouse (A. agrarius), bank vole (Clethrionomys glareolus), common vole (Microtus arvalis) and root vole (M. oeconomus). Results showed, that the dominant species was bank vole, comprising 54,5% of 2004/05 and 49,4% of 2005/06 of the total catch. Decrease of abundance in most species was observed in March and especially April, except the common vole, which became dominant in spring in both years of research. Shannon-Wiener index showed the highest species diversity in March (H=2.12) and November (H=1,672), in most sessions one to three species (maximum five) were trapped. According to Simpson’s index, small mammal community became monodominant in spring of 2005 and in research time of 2005/06 the index saltatory fluctuated. The beginning of breeding of small mammals – of common vole, to be more specific – was registered on the first decade of April of 2005 (the average size of litter was 4.3 embryos per one female) and on the second decade of March of 2006. That is to say, reproduction of bank vole started later – the second decade of April of 2005. It was observed, that there was a tenuous positive correlation between air temperature abundance of small mammals and a significant negative correlation between depth of snow cover and small mammal abundance. Cranial mensuration showed, that despite the fact, that average body weight of bank voles in winter decreased in all age groups, growth of the skull was continuing: three characters were bigger in adult group, seven – in subadults and ten characters – in the group of young voles. In subadults of common voles cranial measurements in winter do not differ from those in autumn. In adult common voles most of cranial measurements in winter were significantly shorter, thus, growth in this species is inhibited. Data for 10 winter-caught yellow-necked mice show uninterrupted growth, especially of subadults, in which most of cranial measurements were longer than in autumn. Our results contribute to insufficient data on small mammal winter data and on craniometry of small mammals in Lithuania, as current publications involve a few cranial measurements of adult shrews, mice and voles without paying attention to their correlation with body weight and seasonal peculiarities of growth. |
