Mediterranean water shrew (Neomys anomalus): Range expansion northward

Abstract

We identified three individuals of the Mediterranean water shrew (Neomys anomalus) in Estonia, expanding the known distribution range of the species to the north by 500 km from the most northern location in Lithuania and over 700 km from Poland. The identification of the species in Estonia, the most northern known locality, was based on the position of mental foramen, height of coronoid process (<4.3 mm), and Libois index (<16.5). Individuals in the northern populations of N. anomalus were smaller than those from southern populations. The most reduced features (by about 10%) are the length of the maxillary and mandibular tooth rows, skull breadth, and height of mandibula. The range expansions require reconsidering known diagnostic characters of the species in comparison with the sympatric N. fodiens as well as the cut-offs for their measurements and, possibly, highlight the need to search for new diagnostic criteria.