Abstract
In the bat-pollinated vine Mucuna holtonii only the first visit to a flower is rewarded with a substantial amount of nectar, which is released when a bat lands on the flower and triggers an explosion mechanism. During later visits the bats receive only small amounts of nectar. Nevertheless, the inflorescences as a whole remain attractive, since further buds successively open during the night. Nectar-feeding bats Glossophaga commissarisi selectively visit unexploded, "virgin" flowers. They can discriminate buds, virgin and exploded flowers using echolocation. In field experiments bats exploited virgin flowers, the vexillum of which had been replaced by a same-sized triple mirror or by an artificial vexillum. Such flowers were frequently inspected, but not as often exploited as natural flowers. In two-alternative-forced-choice experiments the bats learned to discriminate between replicas of the vexillum and triple mirrors. The recognition distance was between 15 and 50 cm. Echoes of the three flowering stages differ in their spectral composition, which changes in dependence of the sound incidence angle in a characteristic way. We conclude that glossophagine bats are able to recognize small motionless structures like flowers and to accurately adjust their landing manoeuvres by using their echolocation system alone.
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Acknowledgements
We gratefully acknowledge efficacious assistance and valuable advice: H. Opel helped to produce the artificial vexilla, Y. Winter gave advice and effective help in all technical problems concerning the training experiments, N. Kondratiev wrote the computer program to control the training experiments, M. Holderied installed hard- and software for the echo measurements, W. Schulze introduced us to the computer aided frame by frame evaluation of the videos and helped with all computational problems. He and M. Bauer prepared the figures. Lee Gass not only improved the English, but he and two anonymous referees gave valuable comments on the manuscript. We are also thankful to Bob Martin and Orlando Vargas at the OTS-station La Selva (Costa Rica), where we conducted the field experiments in 1993–1996. We thank the Costa Rican authorities, especially the Ministerio del Ambiente y Energia and the Area de Conservacion Cordillera Volcanica Central, for research permits. The experiments comply with the current German laws concerning animal care.
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von Helversen, D., von Helversen, O. Object recognition by echolocation: a nectar-feeding bat exploiting the flowers of a rain forest vine. J Comp Physiol A 189, 327–336 (2003). https://doi.org/10.1007/s00359-003-0405-3
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DOI: https://doi.org/10.1007/s00359-003-0405-3