The response of small mammal populations to flooding

Populations of common voles Microtus arvalis (Pallas, 1779), bank voles Clethrionomys glareolus (Schreber, 1780) and yellow-necked field mice Apodemus flavicollis (Melchior, 1834) were studied by live-trapping for two years before and one year after major floods in a flood plain area in central Germany. After floods, the common voles living in undyked grassland died out whereas the population in grassland behind the dyke (control) persisted. Bank voles and yellow-necked field mice in an undyked flood plain forest remained as well. Floods did not decrease survival rates compared to the years prior to floods for bank voles. Survival rates for yellow-necked field mice were highly variable before and after the floods. After floods, reproduction of bank voles commenced later than in previous years while yellow-necked field mice and the common voles on the control plot bred in spring as usual. Young animals were present in the control population of common voles and in the populations of bank voles and yellow-necked field mice in the summer after the floods but not on the flooded grassland. It is concluded that floods have the potential to greatly effect common voles and can lead to low density for at least one growing season. In contrast, bank voles and yellow- necked field mice can continue to thrive after major flood events. By flooding of relevant habitats for short periods of time, combined with other methods of integrated rodent pest management such as grazing, further pressure on common voles could be added to maintain low densities.