More From our Foreign Correspondent: Alex Hiller
Susanne Horne Max Planke Molecular Ecology
Criminal Intent on beaver fossils:
How can you be sure the injured beaver from the road shoulder is not a stranger in the night but legally belongs to its geographical habitat? – Just show a tissue sample to Susanne Horn at Max-Planck-Institute for Evolutionary Anthropology in Leipzig, Germany and get its DNA analyzed.
In her lecture she mentioned a DNA probe of an injured beaver recognizing it as member of the inherent Eurasian beaver species Castor fiber and not of the North American species Castor canadensis it was suspected to be according to the untypical color of its anal gland secretion. DNA research was done on the data basis taken from dozens of tooth and bone samples of ancient beavers throughout Europe.
Beaver Populations can be distinguished even locally by the genetic DNA sequences. Extensive hunt in the 19th century had led to the extirpation of beaver in most parts of Europe except for a few relict populations thus providing a bottleneck in the genetic diversity.
According to the Symposium`s student award winner of the 2nd price, Susanne Horn, “ancient DNA can provide information on the indigenous beavers of a certain area. These results reflecting the history of this species, can now be taken into account by maintenance projects, when planning the relocation of beavers.
Speaking of anal gland secretion (AGS) the 1st price of the student’s award was won by students from Telemark University College, Bo, Norway, on investigation “whether information about age and territory ownership (social status) is coded in the AGS of male Euroasian beavers” ( c.fiber ). Experimental scent mounts in a field study using a free ranging population in Telemark, Norway, as well as chemical analysis confirmed the preliminary suggestions: The older son of a male intruder appeared to pose a greater threat to resident beavers than the younger son and the intruder itself, suggesting “that dominant beavers carry a `territory owner`badge making them perceived as less a threat than beavers without a territory. ( Helga Veronika Tinnesand, Susan Jojola, Frank Rosell )
Regarding beaver territory the participants of the Symposium were shown the findings at a prehistorical beaver site and its suggestions on the development of the beaver species:
Excavations at an ancient peat bog on utmost northern Canadian Ellesmere Island disclosed in its permafrost ground well preserved bones, sculls, claws and teeth of prehistorical beavers as well as hundreds of sizzled sticks with teeth marks at age of 3 to 5 millions of years ago (in short = mya ) just before Ice Age. Natalia Rybczynski of Canadian Museum of Nature, Ottawa, who led the excavations, did research on the form follows function relationship regarding ( 1 ) swimming, ( 2 ) grooming claw and ( 3 ) woodcutting .
Rybcynski`s findings to ( 1 ) were, that the stream-line body , its modified webbed hind feet and modified tail developed 23 mya with its tail as a “propulsive structure” while swimming for getting thrust. The specific form of a flattened tail developed only 5 to 10 mya whereas the ancient grooming claws ( 2 ) had presumably developed 30 to 35 mya and could be distinguished easily by their specific shape different from regular claws at hands and feet throughout millions of years. Woodcutting behavior ( 3 ) could be proved by investigations in National Zoo of Washington, DC: Video analysis of beaver teeth in action cutting wood gave evidence that beaver make use only of one incisor in adjacent position at one side of their jaws, that means beaver gnaw sidewards providing a mean cut width of 60 % of Incisor width. Exactly the same pattern was analyzed on the sizzled sticks of 3 to 5 mya from Ellesmere Island. As a result wood-cutting behavior in beavers is presumed to have developed 23 mya. What still remains to be unsolved according to Rybczinski is the development of dam-building behavior of beavers.
Sticking to the teeth of beaver fossils, Dr. Clara Stefen, Curator of Mammals at Senckenberg Museum of Natural History , Dresden, Germany, presented her research on length to width ratios of upper and lower molars of beaver sculls to determine the evolutionary progress.
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Alex Hiller
