How Eurasian otters (Lutra lutra) use suboptimal habitats? Space use dynamics in forest streams of Central Russian Upland

Abstract

Territoriality is the regulating social system for many carnivore species. It is usually determined by resource abundance and competition. Lutra lutra (hereinafter also – Eurasian otter), a top freshwater predator, has a wide range of various types of resources, which can influence its spatial organisation and space use. It is well known for optimal habitats (mainly wide rivers and lakes). Less is known about the usage of suboptimal habitat. Thus, we focused on forest streams in the Central-Russian Upland and studied the type and dynamics of the Eurasian otter space use with field and genetic methods. During the study period (2002–2018), we showed wave-like changes in the occurrence of the Eurasian otter with a period of nine years. The access to open water is a key factor that affects the Eurasian otter distribution during the snow period, and in the snowless period the water level effects their distribution. We found constant breeding locations, two breeding periods were observed in some years. Analysis of mtDNA control region showed that Eurasian otters with various haplotypes inhabit different river systems of the study area, which could show that the home range of Eurasian otters is determined by one river system. These results show that Eurasian otters use suboptimal habitats as an additional buffer area to survive difficult environmental conditions.