We studied the foraging behaviour and energetics of the nectar-feeding bat, Leptonycteris curasoae (= L. sanborni), in the Sonoran Desert near Bahia Kino, Sonora, Mexico, using radio-telemetry, lighttagging, and focal plant observations to answer three questions: (1) How far do these bats¯y in a night and at what energetic cost? (2) How do they harvest nectar and pollen from columnar cacti that offer large but temporally variable nectar rewards? (3) What are the implications of their foraging behaviour for gene¯ow within populations of their food plants? L. curasoae visited¯owers of three species of columnar cacti in 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. Bats¯ew 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. Within feeding areas, bats visited the¯owers of many cactus plants, visited most¯owers < 5 times, and removed about 0.1 mL of nectar per visit. Although bats¯ew nearly continuously early in the evening, they did most of their feeding between 24:00 and 02:00. When visitinḡ owers of Pachycereus pringlei (cardon), bats apparently waited until¯owers had accumulated 0.8 mL of nectar before feeding, which suggests that rates of nectar secretion in¯uence the timing of feeding in these bats. We estimate that the daily energy budget of L. curasoae is at least 40 kJ and that bats make about 80±100 visits to cactus¯owers to acquire this energy. Foraging areas typically contain thousands of cactus owers, and thus food does not appear to be a limited resource for these bats during the spring. The costef®cient¯ight of this bat makes it an excellent pollen vector for self-incompatible, widely spaced desert cacti.

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Eight black bears (Ursus americanus) outfitted with motion-sensitive transmitter collars were radiotracked from May through December 1984 in the Pisgah Bear Sanctuary in the mountains of western North Carolina. Activities and movement patterns within areas of overlap among neighboring bears were analyzed to determine whether neighbors exhibited spatial or temporal avoidance. The distributions of locations within home ranges were clumped but bears did not use specific areas for specific activities. Home ranges overlapped extensively, and even core areas (areas of high-intensity use) overlapped. Neighboring bears often used areas of overlap for the same activities and at the same time. The clumped or patchy use of areas within home ranges requires analyses that emphasize internal structure of home ranges and not merely outlines or total-area measures.Free-ranging animals do not use all parts of their home ranges in the same way (Burt

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