Five-decade expansion of striped field mouse (Apodemus agrarius) and the process of its establishment in colonized territories

Abstract Range expansion, as an extension of the normal colonization process, is followed by establishment and an increase in abundance. Combining conventional methods with citizen science, a new area of striped field mouse occurrence in Slovakia and progress of their establishment has been investigated. In 2024, fifty years after the first notes of striped field mice spread in eastern Slovakia, the species spread to next ca. 18,600 km 2, representing a 135% increase in species occurrence compared to its initial occurrence in 1973. We observed a dynamic increase of striped field mouse dominance with a peak between 2.7 and 6.8 years after site colonization, followed by a decrease in dominance with a nonsignificant seasonal effect. Results suggested that this rise of dominance is a sign of establishment and “expansion front” overcoming, and represents a mechanism of the spread to other areas.