Agonistic interactions between resident and immigrant sympatric water shrews: Neomys fodiens and N. anomalus

Behavioral mechanisms which control resident-immigrant relations in wild populations of Neomys fodiens (Pennant, 1771) and N. anomalus Cabrera, 1907 were studied by quantitative analysis of agonistic interactions between animals inhabiting the enclosure for at least 1 week ('residents') and animals newly introduced ('immigrants'). Tested animals (46 N. fodiens and 24 N. anomalus) were observed in one- and two-species groups or pairs in enclosures of 275 x 135 x 135 cm built in a laboratory room. During 214 hours of direct observation, social behaviour and patterns of hiding place usage were registered.