RELATEDNESS AMONG FEMALES IN A PEAK PHASE POPULATION OF JAPANESE FIELD VOLES

Spatial and genetic relationships among females in a peak population o f Microtus montebelli were studied by live-trapping and DNA fingerprin ting. In the early period of the spring breeding season, a close gener ic relationship was nor observed between neighboring overwintered fema les, while in the late period, a proximity among highly related female s and a dispersed distribution among intermediately related females wa s observed. These associations among relatives did nor last very long, however, as female pairs who remained in the neighborhood for more th an 150 daps, covering two breeding seasons were not relatives. The pos sibility of cooperation among relatives in this species may thus be lo w, except among philopatric females in the late period of a single bre eding season.