FORAGING BEHAVIOR AND ENERGETICS OF A NECTAR-FEEDING BAT, LEPTONYCTERIS-CURASOAE (CHIROPTERA, PHYLLOSTOMIDAE)

We studied the foraging behaviour and energetics of the nectar-feeding bat, Leptonycteris curasoae (= L. sanborni), in the Sonoran Desert ne ar Bahia Kino, Sonora, Mexico, using radio-telemetry, light-tagging, a nd focal plant observations to answer three questions: (1) How far do these bats fly in a night and at what energetic cost? (2) How do they harvest nectar and pollen from columnar cacti that offer large but tem porally variable nectar rewards? (3) What are the implications of thei r foraging behaviour for gene flow within populations of their food pl ants? L. curasoae visited flowers of three species of columnar cacti i n April through June. Many bats roosted on Isla Tiburon 20 km from the Mexican mainland and commuted about 30 km to the mainland to feed. Ba ts flew for about 5 h each night for a total distance of about 100 km. Individuals foraged alone or in small groups in overlapping areas of 1-3 km(2) and visited the same feeding areas on successive nights. Wit hin feeding areas, bats visited the flowers of many cactus plants, vis ited most flowers < 5 times, and removed about 0.1 mL of nectar per vi sit. Although bats flew nearly continuously early in the evening, they did most of their feeding between 24:00 and 02:00. When visiting flow ers of Pachycereus pringlei (cardon), bats apparently waited until flo wers had accumulated 0.8 mL of nectar before feeding, which suggests t hat rates of nectar secretion influence the timing of feeding in these bats. We estimate that the daily energy budget of L. curasoae is at l east 40 kJ and that bats make about 80-100 visits to cactus flowers to acquire this energy. Foraging areas typically contain thousands of ca ctus flowers, and thus food does not appear to be a limited resource f or these bats during the spring. The cost-efficient flight of this bat makes it an excellent pollen Vector for self-incompatible, widely spa ced desert cacti.