Turning previous studies on the health status of the Eurasian otter (Lutra lutra) population in Schleswig-Holstein into a long-term monitoring program

Project description

In the previous four years a concept was developed to perform standardized necropsy and examination on all otters found dead in Schleswig-Holstein (SH), to allow for assessment of the general population health status. Even though most otters were roadkills and seemed comparatively healthy,, zoonotic agentswere cultured from tissue samples and rare otter specialist parasites were recorded for the first time in Northern Germany.  Combined dietaryanalysis includinghard part analysis and genetic metabarcoding were used to depictthe natural prey spectrum of otters. Knowlegde on the otters` diet is of utmost importance in various context, for example in the light of fisheries-otter conflicts. Cementum aging reveiled a rather young average age of the investigated otters from SH. Combined with the ongoing recolonization of the otter in SH, this might be an indication that the population has not finally established itself yet and we face a dynamic process. The findings of various environmental contaminants of concern in the otters from SH were of utmost importance and included potential microplastic particles, pharmaceuticals, rat poison, mercury or per- and polyfluorinated chemicals.

The aim of this project is to combine the expertise from previous years and transform the health assessments into a long-term post-mortem population health monitoring for otters in SH. As top predators, Eurasian otters are indicator species for environmental contaminants or infectious diseases in freshwater ecosystems, like marine mammals in their habitat. By adopting this indicator function, the collection of otter health data shall be continued to allow for the estimation of time trends in future population health assessments. Accordingly, otters found dead in SH will continued to be collected and investigated, including diagnostics such as histology, microbiology and parasitology. The main focus will be on diseased animals and such, where the cause of death is unclear. All other individuals will be screened for relevant indicator pathogens, including distemper virus or high pathogenic avian influenza virus. In addition, parasitological and microbiological investigations will be conducted if assumed necessary. To determine whether hard ticks infecting otters play a role in the transfer of vector-borne disease, all collected hard ticks (Ixodes) from previous years will be determined on a species level. The results will give an overview, which tick species are infecting otters and if the transfer of certain pathogens might play a role here.

In accordance with their role as indicator species of the aquatic environment, systematic mercury analysis will be conducted for the first time on otters from SH. An international collaboration within the EU investigated contaminants in otters and could show that mercury levels in some individuals from SH were very high compared to other top predators. For the planned analysis, samples from the biobank will be carefully selected to ensure a good coverage with regards to age, sex and location of finding. Moreover, first steps to develop biomarkers for environmental contaminants in otters will be made.

Eine systematische Fortführung der Untersuchungen der Fischotter in SH ist von zentraler Bedeutung, um langfristige Populationsentwicklungen einzuschätzen und beurteilen zu können. Als streng geschützte Art und wertvoller Indikator für das Ökosystem Süßwasser bietet ein strategisches Monitoring des Fischotters die Möglichkeit, Arten- und Naturschutz zu verbinden. Auch im Hinblick auf sich abzeichnende Interessenskonflikte, z.B. mit der Fischerei, kann eine solide Datengrundlage zum Fischotter wertvolle Informationsarbeit leisten und sachliche Diskussionen ermöglichen.

In order to estimate and evaluate long-term population trends of otters in SH, a systemic continuation of the post-mortem investigations is needed. As strictly protected species and suitable indicator for the freshwater ecosystem, a strategic monitoring of Eurasian otter represents a valuable tool to combine conservation of both wildlife and nature. Especially when looking at potential conflicts like the otter-fisheries interface, a well developed dataset on otters will help to create information based on scientific facts and ensure objective rather than emotional discussion.