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Hear my nectar: How dish-shaped leaves attract pollinating bats

Photo montage of a flowering inflorescence of Marcgravia evenia and an approaching Cuban nectar-feeding bat Monophyllus remani.
[Image courtesy of Ralph Mangelsdorff and Ralph Simon]

Bats use high pitched sounds to locate food and navigate. Humans generally can't hear these high pitched sounds. When these sounds bounce off of objects, bats are capable of listening to the returning echoes, which gives bats a sense about the distance, movement and size of all objects in their path—this is called "echolocation".

A new study in the journal Science shows that the dish-shaped leaves above the flowers of the vine Marcgravia evenia beckon bat pollinators by emitting a strong acoustic echo that halves foraging time.

The findings provide some of the first evidence of a flower displaying adaptations to acoustically attract bat pollinators, much the way brightly colored flowers serve to attract pollinating bees and insects.

While large megachiropteran bats, such as flying foxes, may be able to discern visual cues, smaller or microchiropteran bats, known for using sonar to locate their insect prey, likely miss these colorful signals.

Ralph Simon and colleagues show that these unusual echoes of dish-shaped leaves attract bat pollinators by being louder and covering a broader echo detection range than typical leaves; allowing the leaves to stand out amid the chaotic stream of echoes being reflected back from nearby rustling plants.

The researchers trained three nectar-feeding bats to search for a single small feeder — attached to either a typical leaf, a dish shaped leaf, or no leaf. Next, the team measured the amount of time the animals took to find the feeders at different positions, and observed that bats found the feeders with dish-shaped leaves almost twice as fast as those without leaves or with foliage leaves.