Abstract
Nectar-feeding bats show morphological, physiological, and behavioral adaptations for feeding on nectar. How they find and localize flowers is still poorly understood. While scent cues alone allow no precise localization of a floral target, the spatial properties of flower echoes are very precise and could play a major role, particularly at close range. The aim of this study is to understand the role of echolocation for classification and localization of flowers. We compared the approach behavior of Leptonycteris yerbabuenae to flowers of a columnar cactus, Pachycereus pringlei, to that to an acrylic hollow hemisphere that is acoustically conspicuous to bats, but has different acoustic properties and, contrary to the cactus flower, present no scent. For recording the flight and echolocation behaviour we used two infrared video cameras under stroboscopic illumination synchronized with ultrasound recordings. During search flights all individuals identified both targets as a possible food source and initiated an approach flight; however, they visited only the cactus flower. In experiments with the acrylic hemisphere bats aborted the approach at ca. 40–50 cm. In the last instant before the flower visit the bats emitted a long terminal group of 10–20 calls. This is the first report of this behaviour for a nectar-feeding bat. Our findings suggest that L. yerbabuenae use echolocation for classification and localization of cactus flowers and that the echo-acoustic characteristics of the flower guide the bats directly to the flower opening.
Highlights
The increasing interest in information acquisition in natural systems has resulted in the emergence of sensory ecology, the study of how organisms acquire and respond to information about their environment [1,2]
All bats used in our experiments were wild individuals that had never been exposed to any artificial feeder and were used to forage at cactus flowers in the field
We only found a significant effect of distance on the pulse duration (PD), while target type and their interaction showed no significant effects (GLMM; distance: F9, 62.68 = 15.28, p
Summary
The increasing interest in information acquisition in natural systems has resulted in the emergence of sensory ecology, the study of how organisms acquire and respond to information about their environment [1,2]. 165 species has the highest ecological diversity among bats [4,5], with food resources used ranging from fruits, nectar and leaves, to insects, small vertebrates, and even blood [4,6]. In general most phyllostomid species glean food items such as fruits, insects and small vertebrates from surfaces in highly cluttered environments [7,9,10,11]. Almost all phyllostomids recorded so far share a similar call structure: short (mostly 2 ms) frequency-modulated, multi-harmonic, broadband, and low-intensity signals. They have been described as “whispering bats” [4,11,12,13,14]. Recent studies have shown that at least some phyllostomid species emit echolocation calls at much higher intensities than expected and adjust the amplitude, i.e., the intensity of calls, over a large range when not foraging in gleaning mode [9,16,17]
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