Various population indices are widely used to monitor relative population size of many pest and game species to aid their management. However, information on the level of uncertainty associated with their estimates is rarely available. Here we explore sampling and systematic error associated with the index of re-opened burrow entrances which is used extensively in central Europe for surveying common vole populations. We found that relative sampling errors were enormous for low-density populations, attaining almost 400%. However, in high-density populations and for large sample sizes, the relative error dropped below 10% and the estimate is quite reliable. The dispersion of burrow entrances became more clumped at low population densities enhancing further the sampling variation. We demonstrated that the index is related to population size in a non-linear fashion, overestimating the population change at high densities. Consequently, population dynamics of the common vole described by the untransformed burrow index appear more variable than they are in reality.
Between 1996 and 1998, microhabitat selection by three small mammal species was studied in oak-elm forest using the catch-mark-release (CMR) method. Microhabitat selection by these species was assessed by Discriminant Function Analysis (DFA) and Canonical Correspondence Analysis (CCA). Apodemus flavicollis was shown to prefer dense young forest and shrubs, but the presence of dead woody material was also important. In Microtus arvalis the data confirmed a negative relationship with stands with higher tree and shrub cover and a preference for open meadows. Clethrionomys glareolus was found to prefer non-fragmented tree microhabitats, preferring sites with developed undergrowth and ample hiding places amongst fallen logs and branches. Although C. glareolus did not change its microhabitat requirements during the year (spring to autumn), within forest stands it was connected with undergrowth regardless of species composition; this highlights the importance of undergrowth for C. glareolus. Seasonal changes in microhabitat selection could not be confirmed unambiguously.
The anterior jejunum from common vole naturally infected with Giardia microti (Kofoid et Christiansen, 1915) was examined by ТЕМ and compared with the anterior jejunum from control (metronidazole-treated, Giardia-free) common voles (Pallas, 1778). Giardia microti infection resulted in significant diffuse shortening of microvilli and significant greater microvillous diameters. In addition, deformations of the microvilli were observed at the margin of the ventral disc. The microvilli attached to the lateral crest of the ventral disc were vesiculated with a disorganised filamentous core and contained whorled structures resembling “myelin-like figures”. The findings are discussed in context of the Giardia-epithelial cell interaction.