Craniometrical variability of the Eurasian otter (Lutra lutra: Carnivora: Mustelidae) from the Northern Eurasia

Abstract

The analysis of morphometric variability of the Eurasian otter (Lutra lutra) was carried out based on 350 skulls from geographically distant localities throughout the distribution range of this species, including China, Japan, and India. Our study revealed minor craniometric variability in L. lutra, which increases in tropical regions, and also symmetrical change of size and proportions of the skulls in the eastern and western parts of the Northern Eurasia as well as the change of the latitudinal trend in the skull variation approximately between 50 and 55° N. The correlation between the value of the morphological diversity and climatic variables is demonstrated. The Caucasian otter (L. l. meridionalis) shows significant similarity with otters from Europe (L. l. lutra). On the contrary, otters occurring in Honshu Island (L. l. nippon) are well differentiated morphologically from the continental populations. The results of our analysis suggest that L. simplicidens from the Middle Pleistocene of Europe probably represents a fossil subspecies of the Eurasian otter, L. lutra. The hypotheses are formulated about influence of ecological conditions on the the value of the parameters of morphological diversity as well as on the intensity of sexual dimorphism in the L. lutra. The results of our study siggest the higher level of genetic diversity of the Eurasian otter in the eastern part of the Northern Eurasia in comparison with the western part of its distribution range.