Manual of beaver management within the ... - DANUBEPARKS

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Manual of beaver management within the Danube river basinmaturity at about 2/3 of the maximum weight of adults, at minimum age of 1.5 years,after the winter in the second year of life (second winter).Beaver population dynamics is mostly autoregulative, without significant impact ofpredators. Beavers live relatively hidden and are active mainly at dusk and at night.Range of beaver parasites is not very different from other rodents linked to water.Diseases: Tularaemia (so-called Hare plague) caused by bacteria Francisellatularensis, pneumonia and tuberculosis.Parasites: flukes (Trematoda): Stichorchis subtriquetrus (Rudolphi, 1814) in the cecumand rectum (penetration of 80 to 90% of the population). Nematodes (Nematoda):Capillaria hepatica Bancroft, 1893 in liver tissue, penetration of the population up to20%. Mites (Acarina): Schizocarpus mingaudi (Trouessart, 1896). Beetles(Coleoptera): Platypsyllus castoris, Ritz; (Staphylinoidea), feeding on beaver fur andskin.Most important of abiotic factors are floods from May to late August, when the youngbeavers are immobile and unable to cope with the enormous water flow.For beavers of all ages, various technical "traps", like uncovered deep water pits,channels and probes, from which they are unable to climb, are dangerous.In the wild, they can live up to 15 years.3.5. Way of lifeBeavers are highly territorial and mark their area with the caudal gland secretions(castoreum). Musk smell very accurately informs potential intruders about thecomposition of families or condition of individuals. Within their territory, beavers usuallylook for food up to 20 m distance from shore. Occasionally, however, they may moveaway to a few hundred meters. Throughout the year, beavers often do visit the vicinityof their territory, at night they are able to swim up to 20 km. The longest are, however,transfers of young beavers seeking a location for settling and mate.Beavers feed exclusively on vegetation. During the growing season (vegetation period)they are searching for succulent herbs growing in lighted locations, affected byincreased water levels. In the winter, they eat live plant tissues. They prefer juicy youngbark.3.6. The annual cycleBeavers are active throughout the year, do not fall into hibernation. In winter, they diveunder the ice or stay in their burrows. They are less active.In the spring their activity launches by scent re-marking of territory. Simultaneously withre-marking of territory, dispersion migration of sub adults to new territories begins.Impetus to the increase of construction activity is the offspring expectation. In May andearly June, there is a litter of pups. Reproductive burrow is fitted to the safest place inthe territory of a beaver family. The presence of pups stimulates parental couple tobuild more burrows/lodges at a distance of 30 to 200 meters as a shelter for theyearlings who are, after a couple of days, involved in rearing.Peak of activity falls on spring time, when they are rearing youngs or on autumn time,when they prepare for winter.Beavers dissipate into the surroundings, during the vegetation season. At the end ofJuly (August), beavers activate near the burrows. At the beginning of autumn they11
Manual of beaver management within the Danube river basinincrease consumption and in the middle of autumn they begin to gnaw big trees andgather supplies for the winter.Family overcomes winter together and thoroughly prepare for it. In late autumn, theyrepair weirs and dams, improve channels and accumulate stocks of food. They fellmore than 90% of the trees in autumn, until the arrival of frost. Branches of deciduousplants contain the largest amount of nutrients until defoliation. Coniferous trees do notalter much the amount of nutrients in the branches throughout year.3.7. Social structureBeavers are substantially monogamous, and live in permanent families. A typicalbeaver family consists of parent breeding pair, this year's pups and pups from theprevious year (yearlings) - it is thus 4 to 6 (10) individuals.At the beginning of the third year of life, in the spring, young beavers usually leave thefamily nest and search both partner and territory to settle down. Composition and sizeof families also depend on quality of environment. In the case of poor food base orunder severe stress, reduction of the number of young occurs or reproduction iscompletely omitted.Between the members of beaver family, strong social ties exist. They are reinforced bymutual games and rearing of their offspring.3.8. Regulation of population sizeBeavers are very capable fighters. In their current area within the Danube basin,beavers do not have large predators that would hunt them. Population size limits its selfby self-regulation. Territoriality is one of the main mechanisms of autoregulation ofbeaver population.Size of beaver territory depends on quality of aquatic habitat and food supply. In caseof strong population growth, beavers are forced to move borders of territory closertogether, thereby narrowing their district area. Population pressure is also reflected inthe reproduction and individual growth. Stress of a dense population affects growth ofjuveniles, increases morbidity and mortality, weight loss and decreases body size ofanimals. In case of high population density, migratory beavers have little hope to find afree territory. They are aggressively banished from the occupied territories andmortality is, also due to infections in wounds, significantly higher.12
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