Effects of reintroduction of European beaver in the lowlands of the Vistula Basin

Published source details Zurowski W. & Kasperczyk B. (1988) Effects of reintroduction of European beaver in the lowlands of the Vistula Basin. Acta Theriologica, 33, 325-338.
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This study is summarised as evidence for the following.

	Action	Category
	Release translocated/captive-bred mammals in family/social groups Action Link

Release translocated/captive-bred mammals in family/social groups

A replicated study in 1975–1985 in a river basin in north-eastern Poland (Żurowski & Kasperczyk 1988) found that most translocated and captive-bred European beavers Castor fiber released in pairs or family groups survived over one year after release and reproduced in the wild. Ten years after the release of 168 Europeans beavers (74 pairs or families), 108 were found to be established in 64 families. Reproduction was detected in nine of 16 areas where releases occurred and by the end of 1985, forty-four new colonies had established in the reintroduction areas. The average reproduction rate of captive-bred beavers was higher (2.1 kits/litter) than wild-born beavers (1.8 kits/litter; results were not statistically compared). Twenty-two translocated beavers (14%) died during the first year in the wild. In total, 51 beavers died or were lost following translocation. In 1975–1985, a total of 168 European beavers (74 pairs) were released into 16 regions within the Vistula river basin. Release sites had abundant willow Salix spp. and alder Alnus spp. thicket. Beavers were released in small populations of two to 11 pairs (usually 4 pairs), 2–20 km apart. Eleven individuals were captive-born and the remainder were caught in the wild and translocated. Beavers were monitored annually.

(Summarised by: Ricardo Rocha)