Body size and reproductive schedules in two parapatric moles, Mogera tokudae and Mogera imaizumii, in the Echigo Plain.

Abstract

Two species of moles, Mogera tokudae and M. imaizumii, are parapatrically distributed in the Echigo Plain in the northern part of Niigata Prefecture, Japan. The two species are morphologically similar, except for the larger body size of M. tokudae. To clarify whether interspecific competition affects body size and reproductive traits of these moles, we compared these characteristics in syntopic populations with those in allopatric populations for both species in the Echigo Plain. Mogera tokudae exhibited little body size difference between allopatric and syntopic populations, while body size of M. imaizumii in syntopic populations was significantly smaller than in allopatric populations. Although litter sizes of both species were almost the same, reproductive schedules were different. Pregnant M. tokudae were captured mostly in late April, whereas M. imaizumii had a longer period of reproduction from March to October; some individuals bred twice a year. The relatively small body size and the longer breeding period observed in M. imaizumii of the Echigo Plain may be tactics for increasing reproductive success under severe interspecific competition from M. tokudae.