METABOLISM, FOOD CAPACITY, AND FEEDING BEHAVIOR IN FOUR SPECIES OF SHREWS

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Abstract
The metabolic rates of Sorex cinereus, Sorex arcticus, Microsorex hoyi, and Blarina brevicauda were calculated from oxygen consumption, carbon dioxide production, and urinary nitrogen excretion and found to be 6.1, 6.9, 67, and 9.7 Calories per animal per day respectively. The resting rate of oxygen consumption was lower for S. cinereus than values reported by previous authors and was probably close to the basal level. Respiratory quotients were higher than expected for carnivorous animals, averaging 0.83 for all species. Protein catabolism accounted for about half the daily caloric output. Metabolic rate increased with increasing population densities.The minimum numbers of larch sawfly eonymphs required to support the daily metabolic requirements, including fecal wastage, for S. cinereus, S. arcticus, M. hoyi, and B. brevicauda were 87, 123, 98, and 150 respectively. Because of digestive inefficiency and wasteful feeding habits the approximate numbers of eonymphs destroyed daily could be as high as 663, 570, 711, and 150, and if hoarding is considered, 833, 790, 891, and 410 respectively could be taken. Excepting B. brevicauda, the larch sawfly is a preferred food of the group and, when available in abundance, comprises over 70% of the diet. It was estimated that shrews have the capacity to consume numbers of cocoons in excess of naturally occurring populations, but the likelihood of complete destruction of populations is remote. Of the species studied, S. cinereus appeared to be the most likely to provide effective control of larch sawfly populations.