A pulsed-removal experiment on the vole Microtus townsendii

Abstract

A grassland population of M. townsendii was subjected to an alternating sequence of 1 mo. total removal and 2 mo. mark and release for 2 yr. The demographic performance and aggressive behavior of voles from this pulsed-removal area were compared with those of voles from an adjacent control population. The population on the pulsed-removal area increased rapidly from immigration at all times of the year, regardless of whether the control population was increasing or declining. Voles that colonized the pulsed-removal area bred and survived as well as, or better than, voles from the control population. Males and females from the pulsed-removal area showed more submissive behavior when fought in a neutral arena against resident control animals. The subordinate behavior pattern of pulsed-removal colonists was detectable in voles tested 6-8 wk after colonization. Two necessary conditions to show that spacing behavior limits the breeding population of this vole were discussed. Surplus, nonbreeding voles exist in large numbers at all times and can reproduce successfully when the dominant animals were removed.