Understanding the boundaries between chromosome races of common shrews in terms of restricted movement by individual shrews

Abstract

Data on population density, dispersal and homing in common shrews of the Moscow chromosome race are discussed. A population of common shrews is regarded as a set of “independent populations” with each such independent population characterised by their distinctive dynamics in population density. These distinctive dynamics result from the restricted exchange of individuals between the independent populations. The movement of individuals that belong to an independent population is hypothesised to be driven by a network of signals resulting from common activity (tunnels, nest places, pathways etc.) and direct or indirect social interactions (aggression, acoustic communication, scent marks and so on), i.e. Naumov’s “signals field”. Data on year to year fluctuations of population density in two closely located sampling sites were used to reveal independent populations of this sort. Homing experiments were conducted to establish areas through which shrews are most likely to travel. Surveys of micromycetes on the fur support the idea of discontinuity between independent populations. The boundaries between different chromosome races in continuous forests may be explained in terms of the low probability of dispersal of shrews beyond the area of an independent population.