. 1995. Influence of food availability and reproductive status on the diet and body condition of the European lynx in Finland. Acta Theriologica 40: 181-196.The carcasses of the 497 European lynx Lynx lynx (Linnaeus, 1758) killed in two areas in Finland in the 1980s were sexed, the nutritional status and diet of the lynx determined and the breeding stage of the females checked. There was no significant deviation in the sex ratio from 50:50 in any of ten hunting seasons. Fifty-three percent of the females over 1 year of age had given birth the previous spring, the mean litter size from the last pregnancy being 2.33 ± 0.73 (x ± SD, n = 82). In E Finland 86.2% of the winter diet consisted of hares, whereas in SW Finland the lynx consumed hares and white-tailed deer equally. There was no difference in diet between the sexes or age categories in E Finland, but in the white-tailed deer area of SW Finland the male lynx consumed more deer and hares less frequently than the females (p < 0.05). The lynx in SW Finland were on average, in a much better nutritional condition than those of E Finland. The male lynx in both areas had gained more depot fat than the females, on average a difference arising primarily from the smaller amount of fat in the female lynx which had given birth the previous spring. There were positive correlations in E Finland in all the age and sex categories between hare density and mesentery-omentum fat whereas snow depth produced negative correlation coefficients with the mesentery-omentum fat showing a significance of 90% in the adult females.

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Composition of the winter diet, habitat selection and population fluctuations in the mountain hare Lepus timidus were studied in the Värriötunturi fell area, Eastern Finnish Forest Lapland, during the winters 1968/69–1984/85. The three population lows recorded during this 17‐year period followed each other at intervals of 4 and 8 years. During the lows the hares occurred only in the most favoured (forest‐covered) habitats and in two of them they behaved according to the concept of the refuge theory. The mountain birch Betula pubescens ssp. tortuosa appeared to be the most important, but not the most favoured winter food item. When the population crashed, the proportion of birch in the diet decreased, and was replaced especially by juniper which is one of the secondary food items (and is for this reason often discarded although cut). It is suggested that the quality and/or quantity of the winter food (i.e. winter pastures) are one of the driving forces in the population fluctuation of the mountain hare in this area.

Food matter eaten in the first snowless spots early in the spring by capercaillie Tetrao urogallus and willow grouse Lagopus lagopus was studied in Finnish Forest Lapland. When the snow disappears, both species change to feeding mainly on the plants available in the snowless spots, although male capercaillie does not exploit this nutritious diet to the same extent as female capercaillie and willow grouse. Selection in favour of nitrogen and phosphorus‐rich food items, i.e. Betula pubescens, male catkins Eriophorum vaginatum, flower buds, and Equisetum spp., stems and tips, seems to be characteristic especially of the female capercaillie, whose winter diet is poor in these elements. Female capercaillie also feeds on more plant species or different parts of plants at one time than willow grouse, while no differences were recorded between male and female willow grouse in the composition of their spring food. The crowberry Empetrum hermaphroditum, almost regularly produces a bountiful berry crop in northern Finland, and since it overwinters well, it represents an easy source of energy and water available almost every spring. The quality and/or the quantity of the green food matter available early in the spring may fluctuate considerably and be of importance for short‐term fluctuations in the populations of these tetraonid species.