Age structure of the lesser white-toothed shrew (Crocidura suaveolens) population in the Askania-Nova Biosphere Reserve

The aim of this study was to investigate the age structure and reproductive strategy of the lesser white-toothed shrew (Crocidura suaveolens Pallas 1811) population in the Askania-Nova Biosphere Reserve, Ukraine. The age structure of the population of this shrew species was studied in the protected steppe based on specimens collected in 1980–1986. The lesser white-toothed shrew is one of the most abundant species of small mammals in the reserve and a key species of the family Soricidae, which is the main consumer of the local mesofauna. In some periods, its population reaches an abundance of 200–300 individuals per hectare. To determine the age of individuals, we used the degree of tooth wear. The first multicusped tooth of the upper jaw (Pm4) was chosen for age estimation. The ratio of the height of the paracone to its width was used to level out individual variability. An attempt was made to find a correspondence between the relative value of the dental index and the absolute age of the individuals. This was based on the assumption that individuals with the weakest tooth wear (mean index 0.92) correspond to the age of early independent life, i.e. one month. Based on the analysis of the available data, it was found that the rate of decrease in the dental index was 0.026 per 10 days. Pregnant animals were found at the age of 45 days or less, which corresponds to the data of other authors. Based on the data obtained, individuals older than nine months were not captured (dental index mostly 0.26). In the Askania-Nova steppe, the breeding season of the lesser white-toothed shrew mostly begins in April and ends by the first half of October. However, single cases of breeding were recorded beyond this period. In early January, a one-month-old individual was caught. In May, catches of lesser white-toothed shrews aged about five months were recorded. In early July, two individuals aged 6.5 and 7 months were caught. In May, young animals accounted for about half of the captures. By mid-summer, overwintered animals were no longer found. The last cases of catching old animals were noted in the second half of June and early July. The study shows a distinct age structure dynamics of the population of the lesser white-toothed shrew during the year, which is determined by seasonal changes in the reproduction of the population under the conditions of the Askania-Nova protected steppe.