Demographic structure and long-term population dynamics of Muroidea in the Askania-Nova Biosphere Reserve

Abstract

The article presents the results of long-term monitoring of muroid rodent populations in the protected steppe of the Askania-Nova Biosphere Reserve (Ukraine), which lasted from 1981 to 2020, i.e., for almost 30 years. Detailed descriptions of the population dynamics of representatives of two families are presented: the family Cricetidae (four of seven species present in the region) and the family Muridae (three of four species present in the region). The descriptions include data on Cricetulus migratorius, Lagurus lagurus, Microtus socialis, and Microtus levis from the family Cricetidae, and Sylvaemus witherbyi, Mus musculus, and Mus spicilegus from the family Muridae. Detailed data series on the numbers of each species in their main types of habitats (primarily the typical steppe), on the age-sex structure of their populations, distribution of females in reproductive groups, etc. are presented. For some species, the age structure was also analysed by size parameters (primarily by measurements of mandibles from pellets of the barn owl). It was shown that all these species form stable populations, which is ensured by their short life cycle and several reproductive periods per year. A high level of presence was shown for the steppe-specific Cricetulus migratorius, as Lagurus lagurus was recorded almost exclusively in pellets and was virtually absent in trappings, but since 1998 this species has disappeared in pellets. The species Microtus levis was recorded irregularly at the study site with intervals of 10–11 years. In Microtus socialis, population declines, when animals were not trapped at all, lasted for less than two years, and this species occasionally showed population outbreaks. Muridae species are also highly abundant, with Mus musculus inhabiting all biotopes, Mus spicilegus avoiding urban areas, and Sylvaemus witherbyi, though widespread, being rarely found in populated areas. Their populations are characterised by significant fluctuations, ranging from prolonged declines to sharp peaks. Intensive reproduction of all Muridae species occurred in spring, and then pregnant females were found throughout the summer and until mid-autumn, so populations of all Muridae species were periodically replenished with young individuals, which compensated for the short life cycle of these animals.

Keywords

• muroid rodents
• long-term monitoring
• population dynamics
• steppe fauna