Importance of prairie riparian zones to bats in southeastern Alberta

Abstract

The prairie grasslands of North America have undergone tremendous modification due to agriculture. The impact of continued modification is poorly understood because the critical habitat for many prairie species, including bats, is unknown. We investigated habitat use of bats in the vicinity of the South Saskatchewan and Red Deer Rivers in southeastern Alberta using mist-nets to capture bats and ultrasonic detectors to monitor echolocation calls. The majority of echolocation and foraging activity for all species occurred along the river and over small springs. Along the South Saskatchewan River, bat activity was highest near small patches of riparian cottonwood trees. Bat activity, especially for E. fuscus, was also relatively high along the cliffs and coulees of the river valley. Little bat activity occurred over the open grassland. Insect abundance corresponded to the activity patterns exhibited by bats: total insect biomass was greatest along the river and at springs. Bat activity was also related to the steepness and topography of the river valleys. Steep rugged areas along the rivers had significantly higher activity than areas with more gradual slopes. This is likely related to roost availability, as bats in the area roost in rock crevices in coulees. Our study indicates that riparian zones and springs are important foraging habitats for prairie bats. Conservation measures are needed for riparian forests in particular, because water regulation has modified natural flood patterns and reduced recruitment of trees.