Prey availability and foraging activity of grassland bats in relation to urbanization

In general, urbanization negatively impacts wildlife, including bats. However, most urban ecology studies have been conducted in forested biomes and responses of grassland fauna to urbanization are poorly understood. Grasslands are flat, largely treeless, and represent challenging environments to insectivorous bats, which need vertical landscape elements for roosts and often prefer to forage in clutter or along edges. Grasslands may be even less hospitable to bats where agriculture is the dominant land use, as in the Great Plains of North America where intensive pesticide use and livestock grazing are likely detrimental to insects. Compared to agricultural areas that surround them, cities in the Great Plains offer greater structural complexity and an absence of agriculture. We investigated the hypothesis that urbanization benefits bats in the Canadian Prairies by increasing access to insect prey and foraging habitat. In 2007 and 2008, we used sticky traps to sample availability of nocturnal insects, and echolocation detectors to record foraging activity by bats, in and around the city of Calgary, Alberta, Canada. Our data did not support our predictions. Insect biomass and diversity were greatest in rural areas, and foraging activity by bats was influenced more by temperature than by urbanization. Although urbanization does not seem to benefit insects or their bat predators, we found no evidence that it is detrimental to bats in prairie grasslands.