Freshwater mammals as indicators of habitat condition

Abstract

Among the mammals within the current extent of the European Union, there are no truly aquatic freshwater species. There are, however, several species that are semi-aquatic and that in one way or the other are associated with or depend on freshwater habitats. There is also one seal species that inhabits brackish waters in the Baltic Sea as well as the freshwater lake Saimaa in Finland. Sixteen species are defined as being freshwater mammals. All of them are dependent on freshwater habitats, but to different extent. Many of the species have been surveyed in a variety of areas throughout Europe. Commonly, these surveys were aiming at establishing the status of the species itself, not the condition of the habitat the species lives in. The fact that freshwater mammals are not widely used as indicators for condition today does not mean that they cannot be used at all. However, mammals are more demanding than many other organisms. Good population estimates alone may not be very helpful. You have to know well the biology and ecology of your species to understand what in fact it may indicate. As most of the species have a wide geographic distribution, their value as indicator may be different in different parts of their range and should be evaluated at a local or regional scale. It is also important to look at populations of the species rather than single individuals. When looking at populations, we should use long-term population dynamics to assess habitat or site condition and not put too much emphasis on single-season or 1-year observations. © Springer Science+Business Media B.V. 2010.