Diet and diet-associated heavy metal accumulation in an insectivorous bat (Hipposideros speoris) adapted to dwell in two discrete habitats

Abstract

Insectivorous bats provide valuable services to agriculture by suppressing crop pests. However, the possibility of toxic metal accumulation in bats with reference to their diet is understudied. We studied the difference in diet and diet-associated heavy metal accumulation in Schneider's leaf-nosed bat (Hipposideros speoris), a species that lives in two discrete habitats (farm and mine) in southern India. Guano samples were collected from respective roost sites during the dry and wet seasons of three consecutive years (2015−2017). Microscopic diet analysis indicated the presence of insects belonging to six orders (Lepidoptera, Coleoptera, Diptera, Hymenoptera, Hemiptera, and Homoptera). Irrespective of habitat, the probability of finding each insect order in the bat diet was high during the wet season. Guano samples were screened for six heavy metal residues (Al, Co, Ni, Cr, Pb, and Hg); these residues varied across the sites and seasons. Aluminum was detected at significantly higher (∼2.5 ×) concentrations in mine bats (dry season: 7.03 ± 0.60 mg/g and wet season: 7.10 ± 1.44 mg/g) compared to farm bats (dry season: 2.52 ± 0.40 mg/g and wet season: 3.28 ± 0.92 mg/g). Guano contained heavy metals in the following order of concentration: Al, Co, Ni, Cr, Pb, and Hg. Irrespective of seasons, all were found at significantly higher concentrations in guano from mine bats than farm bats. This study, therefore, shows a plausible “habitat effect” on heavy metal accumulation in bats. Further, this study sheds light on the potential use of bat guano as a proxy to measure heavy metals that pass through the food web in different environments.

Keywords

• Bat guano
• Diet
• Heavy metals
• Farm
• Mine
• Seasons