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FLORAL REFLECTIONS
kathryn{at}biologists.com
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Many flowers have made pacts trading their nectar in return for the diner distributing the flower's pollen far and wide. All of the insects and birds that have entered into this arrangement have evolved highly specialised flight patterns and rely on their vision to direct them to the nectar's source. But almost 1000 plant species have opted for a co-dependent relationship with a mammal; tiny Glossophagine bats that can even forage at night. How do these tiny mammals manoeuvre so accurately without the benefit of vision after dark? Dagmar von Helversen, Marc Holderied and Otto von Helversen knew that what bats lack in night vision, they partially make for up with their hearing and sense of smell. Could echolocation direct the bats with the accuracy needed to hover before a flower?
The team began measuring the spectra and distribution of simulated bat sounds reflected from four bell-shaped flowers, and recorded what the bat would hear as it moved around the flower squeaking at high frequencies (p. 1025). Each flower reflected a unique distribution of a subset of the frequencies that the bat emitted, which could help the bat to distinguish a flower from the leafy background. Echoes from the long bell-shaped flowers also lasted longer than reflections from plane objects, and the team suggest that the beam of high intensity sound reflected from the flower's trumpet could help direct the bat to its nectar goal.
References
v. Helversen, D., Holderied, M. W. and v. Helversen, O.
(2003). Echoes of bat-pollinated bell-shaped flowers: conspicuous
for nectar-feeding bats? J. Exp. Biol.
206,1025
-1034.
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