The Eurasian otter (Lutra lutra) as an environmental bioindicator in relation to exotic invasive speciesGiant reed (Arundo donax), Red swamp crayfish (Procambarus clarkii) and American mink (Neovison vison)

Abstract

The Eurasian otter (Lutra lutra, Lineaeus 1758), went through a critical period in the Segura river basin (SE Spain) from the 1960s to the early 1980s, followed by a period of a time of stability during the 1990s, after which it has experienced a slight increase during the 21st century. Thus, depending on the good condition and conservation of the aquatic ecosystems, this semi-aquatic mammal is one of the main apical predators of the River Segura and its tributaries, and it is a potential bioindicator of the environmental situation by the hydrographic network. In this work, the presence with its distribution, the habitat use, and diet of the Eurasian otter have been related to the environmental conditions of the river Segura and its tributaries in the Region of Murcia, based on data obtained mainly within the project LIFE13BIO/ES/001407 RIPISILVANATURA, in order to apply an effective conservation policy for the populations of this threatened carnivore. In the habitat surroundings of their areas of presence an attempt has been made to provide guidelines for a management that considers human activity, with the aim of improving the available information base on the distribution, use of the habitat, response to urbanization, presence of invasive alien species (IAS) and environmental restoration, through the implementation of adequate research and monitoring programs. In the first part of the work, collected qualitative and quantitative data on the distribution of the Eurasian otter in the Region of Murcia, in order to better understand its occupation of the river basin and its relations with environmental management and restoration. To this end, as part of the project RIPISILVANATURA (2014-2019), it is valuing the distribution and use of the habitat in the central section of the river Segura and its tributaries. Between April 2016 and June 2018, 42 sections were sampled for the species' droppings, covering 109.8 km linear of river using the standard method (Macdonald et al., 1987) that foresees the creation of transects of between 600 and 1000m and that it has been visited periodically from 1 to 10 times, to collect and detect remains (feces and gels) of the species. The second step was the study of the diet of the Eurasian otter (Lutra lutra) in the basin of Segura, proceeding with the prey identification to determine the currently nutrition of the animal, distributed by areas with different anthropogenic pressure, and the results were compared with data from 20 years ago. The use of non-invasive genetic methods made it possible to cross-reference data on DNA level (molecular genetics) obtaining information which, together with the typing of the samples, helped to accurately identify both the species and their haplotypes. Last step was the study of the sympatria between the Eurasian otter (Lutra lutra) and the American mink (Neovison vison, Schreber, 1777) a potential invader, and a protocol based on non-invasive genetic methods PCR-RFLP that allowed study the distribution in the water bodies where the two species coexist: Community of Madrid, Province of Guadalajara and Province of Teruel. In conclusion, recommendations were established for the conservation and management of the otter in the basin of Segura, in the framework of ecological restoration actions and in the management policies of IAS in this area.