Abstract
Aggression and the use of vertical and horizontal space in the presence of con- or hetero-specific individuals were investigated in laboratory for Sorex unguiculatus, S. caecutiens, and S. gracillimus in Hokkaido, Japan. S. unguiculatus frequently used the below floor strata of experimental cages or subterranean burrows as their main area of activity, whereas S. caecutiens and S. gracillimus mainly used the cage floor or the ground surface. The presence of con- or hetero-specific individuals led to no changes in any of the three species in the use of space, or in behavioral patterns (active/inactive ; underground/resting/ moving on the ground surface). When two individual shrews were introduced into two interconnected cages, they tended to remain in separate cages, with the exception of S. gracillimus with a conspecific. Dominance rank was highest in S. unguiculatus, intermediate in S. caecutiens, and lowest in S. gracillimus. S. caecutiens attacked S. gracillimus most frequently and S. gracillimus received attacks from S. caecutiens most frequently. The implication of this research is that severe interference competition may occur in the field between S. caecutiens and S. gracillimus.
