The process of changes in the number and morphology of B chromosomes in the populations of mice (Apodemus peninsulae) in the northern region of the Pritelets taiga of the Altai Mountains over a 36-year period (1978‒2014) was traced. Three time phases were distinguished. From 1978 to 2002 (24 years)—a phase of steady growth of the number of B chromosomes, with a relatively uniform average increase of 1.4 chromosomes per decade (from 3.17 ± 0.2 to 6.5 ± 0.54); the phase of stabilization of the indicator when it consistently ranged between 6.3 and 6.9 (2002–2012), although the indicator was at least doubled compared to early 1980s (differences are significant); and the third period (2012‒2014) of the emerging trend of decrease in the number of supplementary chromosomes (differences are also significant). The change in the conditional mass index of B chromosomes (mB) also had similar dynamics, and it was at its maximum for the species during the period of stabilization. The dynamics of different morphotypes of B chromosomes showed an unequal contribution to the overall dynamics. The main contribution was made by large, medium-sized, and small metacentric B chromosomes. Micro-B chromosomes and acrocentrics were absent in the growth phase and appeared in the stabilization phase at the maximum of other indicators.

AbstractIn this study, we examined the effect of synanthropic house mouse (Mus musculus) urine odor on catching probability of small mammals to live traps. We conducted a series of field experiments in August 2016 and 2017 in a natural forests of the northwestern Moscow Region (Russia). Small mammals were trapped at two 4-ha fields using capture-mark-recapture technique by setting 200 live traps (100 points, 2 traps per point) within each field. One trap in each pair was odorless (control) with bait only, whereas the other one was odor-baited with 20 μL of the urine of a synanthropic house mouse. Further analysis was based on the data collected from 2 rodent species (bank vole Myodes glareolus, herb field mouse Apodemus uralensis) and 3 shrew species (common shrew Sorex araneus, Laxmann’s shrew Sorex caecutiens, and Eurasian pygmy shrew Sorex minutus). As a result, only bank voles significantly avoided odor-baited live traps. Using generalized linear mixed models, we showed that the choice of a trap by bank voles depended on their age, whereas the probability of repeated capture to a certain live trap was related to their prior experience. We discuss the possible role of components of synanthropic house mouse urine in the population management of exoanthropic small mammals.

For 35 years, from 1984 to 2019, in the southern Baikal region, observations of changes in the system of additional chromosomes of Korean field mouse (Apodemus peninsulae) were conducted in five regions. The number and structure of morphotypes of additional chromosomes remained statistically constant. Analysis of B chromosome systems demonstrates stability and low variability of statistical indicators over a 35-year period, as well as the lack of statistical differences between samples of different years.

The data on the changes in the cytogenetic structure of the geographic population of Korean field mouse Apodemus (Alsomys) peninsulae Thomas, 1907 at the southern shore of the Teletskoye Lake (Altai Republic) are presented. In 1980 no dot-like microchromosomes were found in 34 mice captured on the southern and northern coasts of the Teletskoye Lake. In 2011, a 1.6-fold (from 2.7 to 4.3) increase in the mean number of B chromosomes compared to the rate estimated there earlier in 1980 was discovered. In 11 of the 15 mice (73%) captured in 2011, the karyotypes contained 1–2 dot-like micro B chromosomes and 1–5 macro B chromosomes. The pollution of the territory by the remains of the rocket fuel components may be an appropriate explanation for the cause of the karyological changes observed in A. peninsulae in this region.

Chromosome sets of eight Apodemus peninsulae individuals captured in Gansu Province (Lianhuashan Natural Reserve) were studied for the first time in 2012. Chromosome sets of mice contained from 55 to 62 chromosomes and included 48 A chromosomes and 7–14 additional B chromosomes of different morphologies.

A new protocol for the identification of two sibling species of voles Microtus arvalis and M. rossiaemeridionalis was proposed by electrophoresis of blood proteins in polyacrylamide gel (PAGE). Animals captured in ten districts of Moscow, Kaluga, and Samara oblasts and Moscow natural territories (1030 individuals), as well as those taken from vivarium collections (five hybrids of the two species), were studied. A comparison of electrophoresis in PAGE, agarose gel, and cellulose acetate plates was carried out. The use of different organs and tissues for species identification was assessed. The relative electrophoretic mobility and the mass of a species-specific blood protein of the southern vole were determined.

In this paper, we analyzed B chromosome variation in Korean field mouse Apodemus peninsulae Thomas 1907 (Rodentia, Muridae) based on a 40-year study of karyotypes collected from geographically distant populations in East Siberia, North Mongolia, China, the Russian Far East, and Japan (Hokkaido). We developed the database of individual variants of B chromosome systems in A. peninsulae. In Siberian populations all animals had Bs. The karyotypes of the studied animals contain from 1 to 30 Вs differing in size and morphology. Analysis of B chromosome systems in 598 individuals from different localities of the range shows the presence of 286 variants of Вs combinations in these animals. Unique sets of B morphotypes make up most of these variants (64.7 ± 1.3%), probably suggesting that individual Bs systems normally result from stochastic processes in the populations. The proportion of animals with a large number of Bs gradually decreases, probably due to increased complexities in the inheritance of large numbers of Bs. A. peninsulae is thus proposed as a good model for studying the origin and evolution of extra elements in the karyotype.

Our hypothesis that exoanthropic forest rodent species (e.g., bank voles) avoid the urinary odor of the synanthropic house mice was tested in field experiments in August 2016. One count of the small mammals was carried out in each of two 4-ha fields by the capture–mark–recapture technique over 12 days. Two hundred live traps (100 points, 2 traps per point) were exposed and controlled twice a day (early in the morning and in the evening) in each count. One trap in each pair served as the reference, while the second was the experimental one with 20 μL of the urine of synanthropic house mice applied to a foam rubber surface every day. Generally, bank voles chose the odorless trap more often (60.8% vs. 39.2%, χ 2 = 3.7, p = 0.054). Adult individuals had a nonsignificant tendency to avoid the odor-emitting traps. Immature (subadult and juvenile) bank voles reliably avoided the odor-emitting traps (a 2 : 1 ratio, χ 2 = 5.74, p = 0.017). A general linear model showed the influence of the age of voles on the choice of the odorless traps. The potential repellent role of sulfur-containing compounds in mouse urine is discussed.

Summer diet of bank voles was studied in 1986-1995 and 2000-2008 in Moscow region forests. We found out that under recreational load the bank voles' forage base bulk increased, in connection with the settlement of abundant tsenofob (weed) plants preferred by these animals; but harvesting and diet selectivity grew lower.