Prey size, prey nutrition, and food handling by shrews of different body sizes

We tested some predictions relating metabolic constraints of foraging behavior and prey selection by comparing food handling and utilization in four sympatric shrew species: Sorex minutus (mean body mass = 3.0 g), S. araneus (8.0 g), Neomys anomalus (10.0 g), and N. fodiens (14.4 g). Live fly larvae, mealworm larvae, and aquatic arthropods were offered to shrews as small prey (body mass <0.1 g). Live earthworms, snails, and small fish were offered as large prey (>0.3 g). The larvae were the high-nutrition food (>8 kJ/g), and the other prey were the low-nutrition food (<4 kJ/g). The smallest shrew, S. minutus, utilized (ate + hoarded) <30% of offered food, and the other species utilized >48% of food. The larger the shrew, the more prey it ate per capita. However, highly energetic insect larvae composed 75% of food utilized by S. minutus and only >40% of the food utilized by the other species. Thus, inverse relationships appeared between shrew body mass and mass-specific food mass utilization and between shrew body mass and mass-specific food energy utilization: the largest shrew, N. fodiens, utilized the least food mass and the least energy quantity per 1 g of its body mass. Also, the proportion of food hoarded by shrews decreased with increase in size of shrew. With the exception of S. araneus, the size of prey hoarded by the shrews was significantly larger than the size of prey eaten. Tiny S. minutus hoarded and ate smaller prey items than the other shrews, and large N. fodiens hoarded larger prey than the other shrews. Copyright 2002.