6533b833fe1ef96bd129b634

RESEARCH PRODUCT

Energy reserves of the capercaillie Tetrao urogallus in finlan

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Abstract 1. 1. The size of energy reserves, distribution of fat stores and the fatty acid composition of subcutaneous and pericardial adipose tissue of capercaillie (Tetrao urogallus) were studied in 12 adult birds shot in Sept.–Oct. and in 8 birds shot in March. Furthermore 4 captive birds were killed in Sept. 2. 2. A capercaillie male can maintain or even increase its body weight during winter, but as shown in the present work it is not a result of increased fat content. 3. 3. In general, capercaillie seems to contain more stored energy in the form of fat than other tetraonids so far studied, except Svalbard ptarmigan. 4. 4. In males total fat content in percentage of body weight varied only from 5.4 (March) to 5.7% (Sept.–Oct.) but in the female fat content decreased from 7.5 in Sept.–Oct. to 2.1% in March. 5. 5. The total fat content of the capercaillie is best predicted by the subcutaneous fat (r = 0.939, total fat % = 0.77 + 0.15 × skin fat %). 6. 6. The fatty acid spectrum was almost identical in both pericardial and subcutaneous fat tissues. 7. 7. Oleic acid (C-18:l) and linoleic acid (C-18:2) were the most abundant fatty acids. 8. 8. The unsaturated fatty acids composed 72.0% in Sept.–Oct. and 65.7% in March. 9. 9. Changes in the thermal conductance seem to be more dependent on changes of the plumage weight (mg/cm2) than on the subcutaneous fat content. It is suggested that the capercaillie prefer lipid metabolism instead of glycogenolytic pathways in adaptation to winter conditions. 10. 10. Capercaillie clearly surpass other tetraonids in the capacity to withstand starvation. 11. 11. The calculated survival time for the male is 8.8 days in Sept.–Oct. and 9.3 days in March and for the female 9.2 and 5.0 days, respectively.