Considerations on the vulnerability of the Eurasian water shrew Neomys fodiens to the presence of introduced brown trout Salmo trutta

Introduced fish represent a major threat for aquatic ecosystems and species and their impact on semiaquatic vertebrates, such as amphibians, has been extensively studied. On the other hand, little is known about their impact on semiaquatic mammals, such as water shrews (Neomys spp., Soricidae), although small mammals have been reported in their diet. The present note reports on a case of predation on an adult Eurasian water shrew Neomys fodiens by a large sized brown trout Salmo trutta belonging to a population introduced in a small pastureland pond in an Italian mountain area. The authors considered that shrews, including relatively large species such as Neomys spp., can be susceptible to predation by introduced fish and they use this finding to discuss about direct and indirect impacts of introduced fish on the populations of shrews inhabiting originally fishless habitats such as headwaters.