Dispersal of Common Shrews (Sorex Araneus L.): The Dream and “An Accident”

Understanding the processes that affect the dispersal distance is essential from perspective of ecology and evolution. It is essential to understand processes that affect dispersal distances. Dispersal distances can may depend on environmental and demographic factors and on the motivation of an individual. Effective dispersal results in the distribution of related genotypes in space. The distribution of pairwise distances between related common shrews (sibs and half-sibs) is characterized by a nonrandom increase in the number of relatives at distances up to 200 m. Aggregations of relatives are formed in a part of individuals dispersed in a random direction to the nearest available home rang (“stright-line search”). The distribution of all distances between relatives (up to 1200 m) is satisfactorily approximated by the straight-line search model and is not consistent with the “spiral search” model as it is; however, the best match can be achieved by combining these two search types. The latter model variant (“mixed search”) assumes that the population includes animals with different personal traits: “superficial” and “thorough” explorers. Thorough explorers search for a vacant territory employing the spiral search strategy and correspond to “dreamers” in the model describing the movement and habitat selection strategy (MHSS). If vacant territories are in deficit and the environment is favorable, dreamers move over long distances and become randomly distributed in space: a random dispersion of related genotypes was recorded at distances from 200 to 1200 m. Therefore, searches for a dream territory in combination with a shortage of vacant territories (an accident) result in a random dispersal of related genotypes within a radius of at least 1200 m. The combination of temporal aggregations of relatives and the dispersal of related genotypes over a vast area explain well the previously discovered combination of an excess of homozygous alleles and a high allelic diversity.