The study of bathymetry, macrozoobenthos abundance and the Russian desman population has been performed in the water bodies located in the Prisurskiy State Nature Reserve buffer zone (River Sura lower reaches floodplain). Twenty-one water bodies were examined in total. In six lakes, Desmana moschata (Russian desman) was absent. In nine lakes, the settlement density was less than 5 burrows per 1 km coastline. And in six lakes, the settlement density was high (i.e. more than 5 burrows per 1 km). The studied parameters of the lake basin included the depth of the lake, the water acidity (pH), dissolved oxygen concentration, the type of the plant cover of the shoreline (forest, shrub, steppe), and anthropogenic load. The taxonomical analysis and individual weighing of the animals in the macrozoobenthos samples were performed. All the parameters were then included to an analysis of the Russian desman density. The factors affecting the density of the Russian desman burrows were revealed. The water bodies having more than five burrows per 1 km along the shoreline are characterised by a higher abundance of macrozoobenthos and especially by the highest mollusk biomass. In turn, the abundance of mollusks, the main food, depends on the dissolved oxygen concentration in the water, trophic state of the lake, and the bottom slope. The highest density of the Russian desman was registered in the lakes characterised by a high biomass of the gastropods Lymnaea stagnalis and Viviparus (Contectiana) contecta. It was noticed that the Russian desman preferred to inhabit wide-course water bodies characterised by a high density of trees or bush along the shoreline. Therefore, the factors mentioned above may appear as the indirect characteristics of the water body with optimal habitat conditions for the Russian desman. Other water body characteristics, such as depth, may define the temporary optimum conditions for the Russian desman inhabiting. The combination of different conditions in a certain area allows the Russian desman to choose suitable water bodies, depending on the annual climatic conditions. There is a combination of a steppe (meadow) and forest areas in the River Sura lower reaches floodplain. Thus, this floodplain may be named as the most suitable for the Russian desman inhabitance.

Since blood cells count is the most important indicator of animals’ physiological status, we investigated the effects of age, litter size, and multiple paternity on the total number of white blood cells, the number of their individual types (lymphocytes, neutrophils, eosinophils, monocytes), and the ratio of neutrophils to lymphocytes in domestic cat during early postnatal ontogenesis. The study was conducted on kittens living in outdoor conditions, aged from birth to 6 months. The number of white blood cells was evaluated using a hemoanalyzer, the leukocyte formula and the proportion of cell types were determined manually from blood smears. Age significantly affected the number of leukocytes in the first 3 months of kittens’ age. The number and proportion of neutrophils were the highest after birth and gradually decreased during the first month. Lymphocytes number, on the contrary, increased during this period. Monocytes and eosinophils increased in number in the first 2 months. The litter size affected the number of leukocytes and neutrophils in the first 2 months of life, their number being significantly higher in kittens from the small litters than from the large ones. In kittens from the litters with multiple paternity, the number of leukocytes and the proportion of neutrophils was higher than in litters from a single male. Thus, age, litter size and type of paternity may affect the hematological indices in domestic cats, which must be taken into account during the estimation of the health status of kittens in domestic and wild cats.