Discrimination of small sugar concentration differences helps the nectar-feeding bat Leptonycteris yerbabuenae cover energetic demands

Abstract

Every day nectar-feeding animals face an energetic challenge during foraging: they must locate and select flowers that provide nectar with adequate amounts of sugar to cover their very high energy needs. To understand this decision-making process, it is crucial to know how accurately sugar concentration differences can be discriminated. In a controlled laboratory setting, we offered the nectar-specialist bat Leptonycteris yerbabuenae the choice between different sugar solutions covering the entire concentration range of bat-pollinated plants (3–33%). When feeding on solutions below 10% sugar concentration Leptonycteris yerbabuenae was unable to cover its energetic demands due to physiological constraints. Their capability to discriminate sugar concentrations outperformed any other nectar-feeding animal studied to date. At sugar concentrations below 15%, Leptonycteris yerbabuenae can discriminate solutions differing by only 0.5%. The bats may utilize this fine-tuned ability to select nectar from flowers with reward qualities that provide them with the necessary amount of energy.