Soil hardness of burrows related to the usage frequencies of the lesser Japanese mole, Mogera imaizumii (Talpidae)

Abstract

. The soil hardness inside burrows was studied in the lesser Japanese mole, Mogera imaizumii , to evaluate differences in the hardness of the ground surface, sidewalls, and bottoms of regular burrows (high usage frequency, R b) and temporary burrows (low usage frequency, T b). We analyzed usage frequency at 68 burrow points by setting snare-type tube traps, which triggered responses by the moles, at each burrow point to record the usage of moles without capturing them. These burrow points were classified as R b or T b based on the presence or absence of a response, respectively, sixteen hours after being set; 20 burrow points were identified as R b, and 48 were identified as T b. No differences in the frequencies of R b and T b were observed relation to the depth, which is related to the vertical gradient of hardness. In addition, newly detected burrows were more frequently found to be T b than in R b during early spring to summer, which seems to be related to mole dispersal. Moreover, we measured the soil hardness of the ground surface, sidewalls, and bottoms of the burrows at the 68 burrow points. On comparisons of the relationships between the soil hardness and the burrow usage frequency, we found that the bottoms were significantly harder in R b than in T b. Therefore, the hardness of the bottom soil in R b is considered to have been caused by the frequent treading of mole movements. to the usage