Southeastern Minnesota bat response to aquatic insect emergences

Riparian areas offer a unique environment to study energy transfers between aquatic and terrestrial habitats. Emergent aquatic macroinvertebrates link terrestrial and aquatic habitats and bats have high foraging activity in riparian habitats and consume aquatic insects. Several studies have found correlations between aquatic insect emergences and bat foraging activity, however, conclusions as to the strength of such interactions vary. Limited research exists on these interactions in the United States, particularly in Minnesota. Emergent aquatic macroinvertebrates and ultrasonic bat calls were collected over 20 nights from 8 riffle sites along Gilmore Creek in Winona, Minnesota. Multiple linear regression was used to determine if: aquatic insect abundance influenced bat activity levels, aquatic insect richness and diversity influenced bat activity levels, and the emergence of any specific aquatic insect taxa predicted bat activity levels. It was determined that bat populations were not responsive to emergent aquatic insect abundance, richness, diversity, or particular insect taxa. The lack of such relationships may be due to several factors including: a low abundance of nocturnal and late season insect emergences, bats preferring terrestrial food sources, or minimal foraging over riffles by bats. Due to limited data obtained here, it is recommended that long-term, cross-seasonal studies be conducted.