Bank voles Clethrionomys glareolus were exposed to odours of seven species of predators (weasel Mustela nivalis, stoat M. erminea, polecat M. putorius, stone ma...

Prey selection, food niche overlap and resource partitioning were investigated in semi‐aquatic Neomys fodiens and Neomys anomalus and terrestrial Sorex araneus and Sorex minutus coexisting in marshland in Białowieża Forest, eastern Poland. Evidence of prey selectivity was found but high levels of overlap, particularly in prey size, reflected the abundance of invertebrates in field samples. Despite similarities in diets between all four species, evidence of niche differentiation was found in terms of foraging mode and prey composition. Neomys ate predominantly terrestrial prey but 20% of prey of N. fodiens was aquatic (compared with 11% in N. anomalus), with Asellus being the dominant aquatic prey. Sorex shrews were exclusively terrestrial in foraging mode. All species ate predominantly small prey (≤5 mm) and these were most abundant in field samples, but small prey were most important for S. minutus. Pairwise comparisons suggested that the most important promoter of resource partitioning was body size, indicating different foraging modes. Food niche overlap was least between species most dissimilar in size. The tiny S. minutus was predominantly an epigeal forager on small Araneae, Opiliones and Coleoptera; the medium‐sized S. araneus fed extensively on Lumbricidae and Coleoptera; and the large, semi‐aquatic Neomys fed on different amounts of freshwater prey in addition to terrestrial prey. Our results support the prediction that microhabitat selection among these species indicates differentiation in foraging mode.

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 0.3 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) 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.