A Biochemical-Genetic Discrimination Method for the two Beaver Species, Castor Fiber and Castor Canadensis, as a Tool for Conservation

Abstract

European beavers, Castor fiber, were recently reintroduced to Austria and Bavaria and the population has been increasing rapidly. In 1996 we began livetrapping animals for reintroduction programs in neighboring countries. There are currently North American beavers, C. canadensis, in Bavaria, and a small number were inadvertently released in Austria 20 years ago. It is critical to be able to discriminate between North American beavers and European beavers that are trapped as part of any reintroduction program in Europe. For our reintroduction work we need to definitatively determine the species of each trapped beaver so no new North American beavers are released. It is also critical to be able to discrimiate between the two species so the distribution of North American beavers in our region may be determined. Discrimination between the two species by morphometric methods is difficult and not definitive using live animals. Preparing chromosomes for karyotypic studies takes time and only works properly with fresh blood. Therefore, we developed a method that uses tissues from either live or dead compare two North American beavers and two European beavers, we only observed variation at the Esterase-D (E.C.3.1.1.1) locus out of the 14 loci examined. To further test our new method of discriminating between the two species we used either animals whose species was already known, or confirmed our results by preparing additional karyotypes. We screened blood and kidney samples from 37 individuals of C. fiber and from 9 individuals of C. canadensis for variation of the Es-D locus by horizontal starch gel electrophoresis. All C. fiber exhibited a fast migrating allele and all C. canadensis a slow migrating allele at this locus. Hence, the Es-D locus can be interpreted as a differential-diagnostic for the two species.