Vegetation cover and microtine rodents spatial distribution under conditions of Nizhny Novgorod oakwood

This paper deals with the problem of the connection between small mammals spatial distribution and the vegetation cover. The study was carried out during the summer period of 2018 and 2019 in the landscape protected area Oakwood of the NNSU Botanical Garden in the province of Nizhny Novgorod. Three relevs were set up in various plant associations: Ulmetum pulmonarioso-asaroso-aegopodiosum, Acereto-Tilietum pulmonarioso-impatienosum (noli-tangerae), Querceto-Acereto-Tilietum asareto-aegopodiosum. A standard geobotanical description was carried out according to the generally accepted method using a series of Raunkier sites registration. Microtine rodents were trapped by standart traps and live traps. The caught animals turned out to belong to 2 genera and 3 species: the bank vole Myodes glareolus Schreber, the pygmy wood mouse Apodemus uralensis Pallas, and the field mouse Apodemus agrarius Pallas. The low population size of animals, as well as the fact that Apodemus agrarius is a co-dominant, may indirectly indicate the anthropogenic pressure in the investigated oak groves. Ecological plasticity of the species Myodes glareolus has been confirmed. Bank voles inhabit micro-habitats with the average data of illumination as well as shaded ones. In general, the vegetation projective cover and the presence of Norway maple undergrowth are crucial for the microtine rodents spatial distribution. Small mammals choose sites with a minimum number of Acer platanoides undergrowth, and gravitate to places where the projective cover of grass has moderate rates (from 35 to 50%). The Principal Component Analysis (PCA) using a vegetation cover species spectrum showed the presence of a significant factor for microtine rodents, which is associated with nitrophilous species (common nettle and touch-me-not balsam). The presence of those plants may indicate a significant anthropogenic pressure on the vegetation cover. In addition, it is important that plants belong to a particular eco-coenotic group. The species Myodes glareolus and Apodemus agrarius differ on the nemoral factor, and their ecological niches do not overlap.

Food of a Chinese jumping mouse, Eozapus setchuanus (Pousargues, 1896)

This note is the only information on food of this species. Food from the stomach was examined using a binocular dissecting microscope. Results from this analysis indicate that the food of this species is similar to that of other zapodids, consisting of several different food items, rather than to the finely ground green vegetation eaten by microtine rodents.

Modelling the spatial population dynamics of arctic foxes: the effects of red foxes and microtine cycles

The Fennoscandian arctic fox ( Vulpes lagopus (L., 1758)) population is critically endangered, possibly because of increased interference competition from red foxes ( Vulpes vulpes (L., 1758)) and fading cycles in microtine rodents, which cause food shortage. It is not known how these factors drive arctic fox population trends. To test their role in arctic fox decline, we developed a spatially explicit and individual-based model that allowed us to simulate fox interactions and food availability in a real landscape. A sensitivity analysis revealed that simulated arctic fox population size and den occupancy were strongly correlated with fecundity and mortality during the microtine crash phase, but also with red fox status. Model simulations suggested that arctic fox population trends depended on microtine cycles and that arctic fox distributions were restricted by red fox presence. We compared the model predictions with field data collected at Vindelfjällen, Sweden. The model recreated the observed arctic fox trend only with the inclusion of arctic fox avoidance of red fox home ranges. The results indicate that avoidance behaviours can affect population trends and hence that relatively small numbers of red foxes can have a strong negative impact on arctic fox population size and distribution.

Are silica defences in grasses driving vole population cycles?

Understanding the factors that drive species population dynamics is fundamental to biology. Cyclic populations of microtine rodents have been the most intensively studied to date, yet there remains great uncertainty over the mechanisms determining the dynamics of most of these populations. For one such population, we present preliminary evidence for a novel mechanism by which herbivore-induced reductions in plant quality alter herbivore life-history parameters and subsequent population growth. We tested the effect of high silica levels on the population growth and individual performance of voles ( Microtus agrestis ) reared on their winter food plant ( Deschampsia caespitosa ). In sites where the vole population density was high, silica levels in D. caespitosa leaves collected several months later were also high and vole populations subsequently declined; in sites where the vole densities were low, levels of silica were low and population density increased. High silica levels in their food reduced vole body mass by 0.5% a day. We argue that silica-based defences in grasses may play a key role in driving vole population cycles.