SUMMER AND AUTUMN TEMPORAL ACTIVITY OF THE MONTANE VOLE (MICROTUS-MONTANUS) IN THE FIELD

Because little is known of the temporal activity of the montane vole ( Microtus montanus) under natural conditions, this field study was unde rtaken to elucidate the summer and autumn activity patterns. Laborator y studies suggest this species is more nocturnal when subject to long photoperiods that simulate summer conditions. The temporal activity of the montane vole was continuously monitored 3-5 days/week May-Novembe r, over two successive years, in an old-field grassland in southeaster n Washington. Live traps, instrumented with timer mechanisms that docu mented capture times, were checked twice daily. Voles were active at a ll hours of the day and night but both sexes and all age groups were p redominantely diurnal. In June, September, October, and November, 1989 , the diurnal activity was significantly greater than expected (p < 0. 05). A diurnally bimodal activity pattern was apparent during the summ er months. Activity was reduced during the highest daytime temperature s. It it suggested that photoperiod, ambient temperatures, energetic r equirements, predatory pressures, and interspecific competition may in fluence the temporal activity pattern.