Cyclic voles and shrews and non-cyclic mice in a marginal grassland within European temperate forest.

Cyclic population dynamics of small mammals are not restricted to the boreal and arctic zones of Eurasia and North America, but long-term data series from lower latitudes are still less common. We demonstrated here the presence of periodic oscillations in small mammal populations in eastern Poland using 22-year (1986-2007) trapping data from marginal meadow and river valley grasslands located in the extensive temperate woodland of Bialowieza Primeval Forest. The two most common species inhabiting meadows and river valleys, root vole Microtus oeconomus and common shrew Sorex araneus, exhibited synchronous periodic changes, characterised by a 3-year time lag as indicated by an autocorrelation function. Moreover, the cycles of these two species were synchronous within both habitats. Population dynamics of the striped field mouse Apodemus agrarius was not cyclic. However, this species regularly reached maximum density 1 year before the synchronized peak of root voles and common shrews, which may suggest the existence of interspecific competition. Dynamics of all three species was dominated by direct density-dependent process, whereas delayed density dependent feedback was significant only in the root vole and common shrew. Climatic factors acting in winter and spring (affecting mainly survival and initial reproduction rates) were more important than those acting in summer and autumn and affected significantly only the common shrew. High temperatures in winter and spring had positive effects on autumn-to-autumn changes in abundance of this species, whereas deep snow in combination with high rainfall in spring negatively affected population increase rates in common shrew.

Trade-offs between activity and thermoregulation in a small carnivore, the least weasel Mustela nivalis.

We studied factors influencing daily energy expenditures (DEE) of male least weasels (Mustela nivalis) using the doubly labelled water technique. The relationship between ambient temperature and DEE formed a triangular pattern, characterized by invariance of the maximum DEE and an inverse relationship between minimum DEE and temperature. A simple energetic model relating the DEE of male weasels to activity time (AT) and ambient temperature predicted that, across seasons, less than 10 per cent of measurements approach the upper bound of observed DEE. Male weasels were able to maintain a relatively constant maximum energy output across varying temperatures by adjusting their AT to changes in temperature. They achieved maximum energy expenditures in winter due to high thermoregulatory costs, and in spring and summer due to high levels of physical activity. This pattern exemplifies a 'metabolic niche' of a small mammal having extremely high energy expenditures primarily driven by ambient temperature.

Habitat requirements of weasels Mustela nivalis constrain their impact on prey populations in complex ecosystems of the temperate zone.

Differences in habitat use by prey and predator may lead to a shift of occupied niches and affect dynamics of their populations. The weasel Mustela nivalis specializes in hunting rodents, therefore habitat preferences of this predator may have important consequences for the population dynamics of its prey. We investigated habitat selection by weasels in the Bialowieza Forest in different seasons at the landscape and local scales, and evaluated possible consequences for the population dynamics of their prey. At the landscape scale, weasels preferred open habitats (both dry and wet) and avoided forest. In open areas they selected habitats with higher prey abundance, except during the low-density phase of the vole cycle, when the distribution of these predators was more uniform. Also in winter, the distribution of weasels at the landscape scale was proportional to available resources. In summer, within open dry and wet habitats, weasels preferred areas characterised by dense vegetation, but avoided poor plant cover. In winter, weasels used wet open areas proportionally to availability of habitats when hunting, but in contrast to summer, they rested only in habitats characterized by a lower water level, which offered better thermal conditions. At the local scale, the abundance of voles was a less important factor affecting the distribution of these predators. Although we were not able to provide direct evidence for the existence of refuges for voles, our results show that they may be located within habitat patches, where availability of dense plant cover and physiological constraints limit the activity of weasels. Our results indicate that in complex ecosystems of the temperate zone, characterized by a mosaic pattern of vegetation types and habitat specific dynamics of rodents, impact of weasels on prey populations might be limited.

Therapy of iatrogenic subglottic stenosis: a steroid/antibiotic regimen.

The authors have evaluated the efficacy of a medical regimen, consisting of systemic antibiotics and steroids, in the management of acute iatrogenic subglottic stenosis. The study consisted of the infliction of a standardized subglottic injury to three groups of five dogs: Group I animals were placed on prednisone 1 mg/kg/24 hours and potassium phenoxymethyl penicillin 50 mg/kg/24 hours from the day of the trauma. Group II were placed on a similar regimen from the eighth day after subglottic trauma. Group III received no medical therapy at all. Therapy was continued in treated Groups I and II for five weeks. At the end of the study the dogs were sacrificed and the final degree of subglottic stenosis evaluated, at which time the laryngotracheal complexes were submitted for pathological evaluation. A significant difference was found between the degree of stenosis attained in the three groups. The study suggests that the introduction of a steroid/antibiotic regimen has a beneficial effect in developing subglottic stenosis and that the timing of such therapy is of importance.