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

The metabolic rates of Snsex cinereus, Sovex arcticas, M<~osorex koyi, and Blurirza bresimttda were calculated from oxyEen consumption, carbon dioxide production, and urinary nitro~erl excretion and found to be 6.1, 6.9, 6.7, and 9.7 Calories per animal per day respectively. Thc resting rate of o.xygen mnsumption was Iower for 3. cinererts than values reported by previous ai~thors and was probably clove to the basal level. Respiratory quotients were higher than expectd lor carnivorous animaIs, aversqing 0.83 lor all spies. Protein catabolism accounted for about half the daily caloric output. Metabolic rate incrcaxrl with increasinq population densities. The minimum numbers of larch sawfly eonymphs sequinxi to support the daily metabolic req~~iremcnts, including lecal wastage, for S. cinereus, 5, ardic*rs, M. kyi, and B. brmkallda were 87, 123, 9.8, and 150 respectively. Because of digestive inefficiency and wasteful fewling habits the approximate nr~mhcrs of mnymphs desrroyed daily co~~ld be as high as 663,570,711, and 150, and il hoarding is considcrd, 833, 7'10, 891, and 410 respectivelv cotrld be taken. Excepting B. hrmkuzcda, the larch s~dy is a preferred food of the group and, when available in abundance, comprivcv over fOCi, of the diet. It was estimated that shrews have the capacity to consulme numbers of cocwns in excess of naturally occurring populations, but the Iikelihood 01 complete destruction of popuIations is remote. Of the species studied, S. ciinarms appeared to be the most likely to provide effective control oI larch sawfly populations.