Characterization of the Temperature Conditions of Inside Narrow Rocky Outcrops that Serve as a Habitat for Semi-Fossorial Mammals

We characterized the temperature conditions inside narrow rocky outcrops that served as habitats for semi-fossorial small mammals in a mountainous locality on the Japanese Islands. Usually, it is considered that the narrow rocky outcrops have poorer resources than the soil ground of forest floors, which have rich vegetation and nutrition. On the basis of this tendency, it is considered that ecologically dominant species occupy the rich soil habitats and subordinate species are chased away to the narrow rocky outcrops by ecological species competitions, resulting in habitat segregation. However, the present temperature data revealed that the temperatures inside rocky terrains were more stable than the shaded ambient temperatures in the forest. The rocky habitats were apparently colder in summer and warmer in winter, in both daily maximum and minimum temperatures, than the ambient temperatures in the forest during the research period. In addition, the daily difference between maximum and minimum temperatures in the rocky habitats was apparently smaller than that of the ambient ones. These temperature conditions in the narrow rocky outcrops are advantageous to the small mammalian metabolic system. Namely, we estimate that the semi-fossorial small mammals are not chased out by the dominant species through ecological competitions and that the semi-fossorial small mammals may occupy the narrow rocky outcrops as a more advantageous habitat than the forest floor.