Seasonal and age changes in the metabolism and activity of Sorex araneus Linnaeus 1758

Abstract

The oxygen consumption of the Common shrew, Sorex araneus L. wa s measured in 70 daily runs, using a closed-circuit respirometer. The shrews wer e divided into fiv e groups covering the whol e life cycle of thes e animals: young adults (summer, autumn, winter) and old adults (spring, summer). In young adults the average daily metabolic rate is 9.91 cc 0 : / g hr (daily requirement — 8.847 kcal per animal) in summer, 9.67 (8.533) in autumn, 9.66 (7.478) in winte r and in old adults 9.29 (9.953) in spring and 8.28 (11.093) in summer . The seasonal fluctuations in the metabolism of shrews are smaller than in rodents and cannot be investigated in abstraction from the age of animals. Oxygen consumption wa s measured in 8—12 shrews at temperature s of 7, 10, 15, 20, 25, 30, and 35°C in summe r and in winter . The value s for summe r are higher than those for winter. In the winte r the thermoneutral zone lies within limits of 10—15°C, wherea s in the summe r it ranges from 15 to 20°C. The results support the opinion of the authors wh o claim that the metabolism of shrews is higher than it might be inferred from the general interrelations between the animal size and its metabolism. In the author's opinion this fact results both from the relation between the weight and the surface area of the body, which is more unfavourabl e than in bigger animals, and from the specifi c dynami c action of food. Short cycles, connected with the frequency of food intake, change with season and, in S. araneus, last from about one hour and a half in winte r to about 2V2 hours in summer . The pattern of daily activity (traced on the basis of the rhythm of oxygen consumption) is also dependent on the animal age and on season. It is bimodal in autumn, winter, and spring and unimodal in young adults in summer . Old adults are nearly uniformly active in the daytime and at night in the summer.