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2 Acta Theriologica

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Diet of otters Lutra lutra in central Finland

100%

Sulkava R.

Acta Theriologica

1996

tom 41

nr 4

The diet of otters Lutra lutra (Linnaeus, 1758) in central Finland was studied in 1988-1993 by analysing 1506 spraints. The main components of the diet of otters are fish and amphibians. The most important fishes for otters are small (body length mostly less than 15 cm) cyprinids, perches and pikes. The composition of food varies seasonally. In winter amphibians are the most important prey (33.2% of all food). Perches, pikes and cyprinids are important during all seasons, but in winter small sculpins (9.8% of the food) and burbots (8.9%) are also important. In spring the most important prey are cyprinids (38.7% of the food). Amphibians are important, especially in the smallest streamlets (in winter, 68.4% of the food). Otters also eat toads Bufo bufo. In some areas crayfish and mammals are quite important; but for most otters in the study area salmonids, birds, reptiles, insects, moliusks and plants are only occasional food. Most of the otters in the study area live in small forest rivers. In central Finland in winter amphibians and sculpins are of great importance for otters living in small rivers.

Population fluctuations of the wood lemming Myopus schisticolor in Eastern and Western Finland

51%

Eskelinen O. , Sulkava P. , Sulkava R.

Acta Theriologica

2004

tom 49

nr 2

From 1982 to 2003 we studied fluctuations in populations of the wood lemming Myopus schisticolor (Liljeborg, 1844) in the Heinävesi (eastern Finland) and Keuruu regions (western Finland) by counting field signs and dead animals in standardized field surveys. We compared the population fluctuations of lemmings to those of other voles, owls and small mustelids in these regions. The lemming population in Heinävesi fluctuated regularly in 3-year cycles and in synchrony with the field vole popu- lation. i Populations of owls also fluctuated in synchrony with wood lemming and field vole populations. In the Keuruu region, oscillations in the wood lemming population were irregular, and neither lemming and vole populations nor lemming and owl populations were correlated. Although direct mechanistic evidence is lacking, specialist predators such as weasels and owls probably cause the cyclicity in the field vole and wood lemming populations in the Heinävesi area. On the other hand, scarcity of high-quality habitats, unfavourable winter weather conditions and generalist predators may prevent the development of cyclicity in the wood lemming population of Keuruu.