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Pathomorphological Changesin the Small Intestine and Liver of the European Beaver (Castor fiber L. 1758): a case study.The aim of thestudy was to examine and describe the morphology and patomorphology of small intestine and liver of European beaver (Castor fiber). In natural environment beavers are in constant contact with various both internal and external parasites. Histological analysis revealed the pathological changes within the digestive track and liver indicating long-term inflammation. It was hypothesized that the observed inflammation was caused by the parasites not related to beavers so far.
The impact of the European beaver Castor fiber on deadwood resources near dams on the rivers of Wigry National Park (northeastern Poland) has been analyzed. The river sampling area was subdivided into the flooded zone, scarp and upland. We found that beaver feeding was limited to the flooded zone and the scarp. Within a distance of 40 m of the river, beavers browsed 75% of all deadwood pieces (wood debris, stumps, dead trees). The wood generated via direct browsing by beavers made up 5% (3.29 m³/ha) of the total wood volume and 35% (641 pieces/ha) of the total number of wood pieces in this region. The beavers mostly left small pieces of wood (with a mean diameter of about 4 cm) at an area after feeding. The deadwood volume and number of pieces were significantly different in front and behind the dam only in the flooded zone. The volume of deadwood in front of the dam in the flooded zone was higher by 65% than behind the dam (102 and 62 m³/ha, respectively), and the number of pieces was higher by 75% (2200 and 1200 pieces/ha, respectively). We prove that beavers generate the majority of dead wood indirectly – by flooding a part of the area. This results leads to conclusion that frequent flooding of a given area may lead to limiting the source of deadwood in the long term. We also confirm that through direct browsing, beavers produce small amounts of thin dead wood with less usefulness for other groups of animals, thus in this way beavers are not able to provide high-quality deadwood resources.
Partial sequence of mitochondrial ND1 gene was obtained from a hepatic cyst found in European beaver in the North-Eastern Poland. The sequence was identical to the previously published sequences of the G7 (pig) strain of Echinococcus granulosus. This is the first finding of the E. granulosus from European beaver.
Subspecific relationships of the European beaver Castor fiber have been obscured by failure to follow the rules of the International Code of Zoological Nomenclature and remain an open issue. Inconsequence in the use of subspecies names caused a nomen- clatural as well as a taxonomic confusion. We discuss these controversial and incorrect nomenclatural decisions, and recognize 9 nominal subspecies of European beaver, bearing 9 available names: C. f. fiber Linnaeus, 1758, C. f. galliae Geoffroy, 1803, C. f. albicus Matschie, 1907, C. f. vistulanus Matschie, 1907, C. f. pohlei Serebrennikov, 1929, C. f. birulai Serebrennikov, 1929, C. f. tuvinicus Lavrov, 1969, C. f. belorussicus Lavrov, 1981, and C. f. orientoeuropaeus Lavrov, 1981.
In this study, generic composition of food and foraging preferences of the European beaver were determined on sites where the beavers were reintroduced after more than 200 years of absence. Research area was located on lowland (Silesian Lowland) and highland habitats (Bystrzyckie Mountains, Wałbrzyskie Mountains) in western Poland. During the study period, 17,418 trees and shrubs growing within the feeding area of the beavers were marked, out of which 4,669 were found to be cut by beavers. The results showed that the foraging preferences of beavers depend on the availability and diversity of the local food sources. In the lowlands beavers preferred the following species of trees and shrubs as their primary food source: Salix cinerea, S. fragilis, S. caprea, Cornus sanguinea and Populus tremula. In the highlands, beavers preferred Corylus avellana, Sorbus aucuparia, and Fagus sylvatica due to the low availability of Salix and Populus species. Moreover, in the highlands, beavers had to cover longer distances to reach the feeding sites and had to cut trees with larger diameter than in the lowlands.
The study on the distribution and abundance of beaver families in the Augustowska Primeval Forest was conducted in the years 2000 -2003. It embraced all seven Forest Inspectorates administering the Forest. The study consisted in the penetration of banks along watercourses, lakes and drainage ditches. Lodges, bank dens, dams and the length of the banks colonized by beaver families were plotted on maps. Habitat types contained within the territories of individual beaver families were established on the basis of the maps obtained from Forest Inspectorates. The percentage of bank utilisation by beavers in various types of water bodies was determined. The number of beaver lodges and bank dens, as well as their number per family were established. Also, habitat preferences of beavers in individual water bodies were verified. The presented study has the form of a report which can be used for further monitoring of beaver populations in the Augustowska Primeval Forest.
Lipids obtained from the muscular and adipose tissues of the European beaver were isolated by the modified Folch method. Fatty acids were converted to methyl esters and separated by high-resolution gas chromatography (HR-GC). The content and composition of beaver fat depended on the sex of a given animal. The adipose subcutaneous tissue of the female contained the most fat (approximately 70.5%). The fat content of muscular tissue was very low in both male and female beavers. Adipose tissue lipids of the beaver contained fatty acids ranging in chain length from 12 to 22 carbon atoms. Polyunsaturated fatty acids have the highest proportion in of total FA content of adipose tissue in the beaver, which distinguishes these lipids from the lipids of adipose tissues in other mammals. The results of the present study also confirmed a unique FA composition in the tail fat of the beaver, including a very high content of alpha-linolenic acid (ALA, 18:3 n-3) (on average 20.0%) and the sum of n-3 fatty acids (on average 20.45%). In addition, a very low content of the sum of saturated fatty acids (on average 14.93%) was observed, and an extremely low content, as for animal fat, of palmitic acid 16:0 (on average 10.53%).
Cephalic arteries of 17 European beavers Castor fiber Linnaeus, 1758 were ex­amined. After the common carotid arteries were injected with resin, the heads were biologically macerated. Differences between individual specimens as well as asym­metrical distribution of certain arteries were noted. It was found that in the European beaver the common carotid artery divided into external and internal carotid arteries. The internal carotid artery is well developed in C. fiber, whereas in some other rodents it may be obliterated. The examined beavers had no stapedial arteries.
Observations on the building activity of European beavers, Castor fi ber Linnaeus, 1758, were carried out in two dissimilar lakelands in Poland to which beavers were being reintroduced from 1974 to 1985. Reintroduced beavers occupied 62 sites, and lodges were built in 76% of the sites. Several sites contained two or more lodges. Most lodges had a circular or oval base (83%) and a conical side view (85%). The size of lodges differed significantly {p = 0.051) between the two lakelands, with larger lodges at sites characterized by water scarcity. Beavers built lodges immediately after their settlement in 50% of sites, while in the other sites lodges appeared 1-8 years later. Lodge construction is frequently related with the first appearance of kits. In the study area beavers built 27 dams in 17 sites, apparently to improve water conditions and to get safe access to new stores of winter food. Dams usually wore built without acoustic stimuli. Behaviour of reintroduced beavers suggest threat as their main motivation for any building activity.
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