Nectar concentration preference of flower visiting bats Glossophaga soricina antillarum was studied in the laboratory. In a series of dual choice tests using sugar concentrations from 10 to 80 %, the bats preferred the higher nectar concentration up to a maximum of 50 %. When presented simultaneously with nectar and additional water, the bats took more water, depending on the nectar concentration offered. The regular distribution of nectar and water intake during the activity period resulted in a roughly constant mean ingested concentration. Its maximal value agreed with that of the preferred nectar concentration, indicating that water needs played a role in determining the upper limit of an acceptable concentration. In preliminary experiments with ad libitum-feeders, sugar intake rate was maximal at 60 % despite the high viscosity at this concentration. Results are discussed in relation to the evolution of nectar concentration in bat-pollinated flowers.
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