The oxygen consumption of the Common shrew, Sorex araneus L. was measured in 70 daily runs, using a closed-circuit respirometer. The shrews were divided into five groups covering the whole life cycle of these 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 winter 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 was measured in 8-12 shrews at temperatures of 7, 10, 15, 20, 25, 30, and 35°C in summer and in winter. The values for summer are higher than those for winter. In the winter the thermoneutral zone lies within limits of 10-15°C, whereas in the summer it ranges from 15 to 20°C. The results support the opinion of the authors who 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 unfavourable than in bigger animals, and from the specific dynamic 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 winter 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.
Food habits of voles Clethrionomys glareolus (Schreber, 1780) and mice Apodemus flavicollis (Melchior, 1834) were studied in the beech forest in Ojców National Park near Cracow. The food preference was studied using choice test; stomach contents were microscopically analysed. In the laboratory the animals were prefering similar food to that consumed in the forest. The voles can consume variable kinds of bulky and concentrated food, while mice are eating mainly concentrated food. In the natural food of voles greens and seeds are prevailing (the average of 44 and 40% of stomach contents, respectively) the remainder being composed of invertebrates and fungi (9 and 7%). Mice in the natural habitat are consuming mostly seeds (74% of volume) and invertebrates (15°/o); much less greens and fungi (10 and 1%, respectively). In the beech forest potential food of voles is composed of herb vegetation, tree seeds and, to much smaller extent, fungi, insects, leaves, buds and tree twigs. Seeds and insects are the main food of mice. In addition some fungi and herbs are eaten. For these rodent species the food supply in beech forest was estimated to be 1,949,000 kcal/ha/year for the vole and 1,085,000 kcal/ha/year for the mouse. The food available to these rodents amounts only to 4.4% and 2.4% of the yearly primary net production of the studied forest. I. INTRODUCTIONIn the studies of energy flow through the populations of small rodents, the food consumed by these animals is usually compared with the total primary net production of ecosystem. However, the majority of ecologists studying this problem takes into consideration that food available to rodent is only a part of plant production. The energy available for rodents was defined by Grodziński (in litt.) as "the food which is easy to find and is being chosen and eaten by these animals". Consequently, it is difficult to estimate plant production "from the point of view" of a mouse or a vole; food habits of these small mammals have to be known in some detail.Such estimation is troublesome and was usually quite arbitrary. In the old--fields community all live parts of plants above the ground were considered as a food available to Microtus pennsylvanicus
The daily energy requirement of the yellow-necked field mouse is 0.467 Kcal/g/day in summer, 0.551 in autumn, 0.413 in winter and 0.505 in spring. This was calculated from the mean daily oxygen consumption with the corrections for the influence of temperature on heat production (thermoregulation) and the increased requirement during the gestation and lactation. The daily energy budget of field mice from the Białowieża population in summer is 12.347 Kcal/animal/day (mean body weight -26.44 g), in autumn -15.747 (28.53 g), in winter -11.176 (27.06 g) and in spring -12.130 (24.02).
Measurements were made of the length and weight of the alimentary tract (without the esophagus) in 282 individuals of Microtus oeconomus, at different seasons. These were both young, sexually immature individuals and adult, sexually mature animals, including pregnant and nursing females. The length and weight of the alimentary tract increase with age, but this increase proceeds more slowly than growth of the whole body. In young voles the alimentary tract is relatively larger than in older individuals. In nursing females the length and weight of the alimentary tract are greater than in pregnant females. Hypertrophic changes during gestation and lactation are greatest in those species of rodents feeding on concentrated diets, and the size of their alimentary tracts is relatively small (rat, Apodemus flavicollis). These changes are smaller in rodents feeding on both concentrated and bulky foods and which possess relatively larger alimentary tracts (Clethrionomys glareolus). They are most weakly expressed in M.oeconomus, a typical graminivore with a large alimentary tract.
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