Bats Like Their Plant Nectar Sweet — Though Maybe the Plants Know Better

Jan 8, 2017

By Steph Yin

This is how we’re taught to count as children: 1, 2, 3, 4, 5. Yet our innate grasp of quantities isn’t linear. We’re more likely to experience the world in ratios, like 1, 2, 4, 8, 16. It’s easier for us to see the difference between one and two marbles than 15 and 16 of them.

In this way, we’re a lot like certain types of bats who have shaped the evolution of the plants they pollinate by making proportional judgments about what they’re willing to eat. That’s the finding of a study published in Science on Thursday. The study set out to answer an old evolutionary riddle: How do plants pollinated by bats get away with offering nectar in much lower sugar concentrations than the bats prefer? It turns out the plants are just giving the bats what they appear to want.

Given a choice through experiments, bats choose syrupy nectars, with 60 percent sugar — but the plants they pollinate in the wild produce watery nectars with 20 percent sugar.

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4 comments on “Bats Like Their Plant Nectar Sweet — Though Maybe the Plants Know Better

  • I think the answer is simpler. If bats receive more dilute nectar, they will have to make more visits to get the same amount of sugar. That means more pollination.

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  • Roedy

    Also, do we know how much sugar is actually good for the bat? Can a bat have too much sugar and not live as long as others? Seems the balance between two things in evolution is the simpler answer, yes.

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  • @OP – link – Nectar-feeding bats also consider two things at the same time: the volume of available nectar, and its sugar concentration. They prefer high levels of both, but in the wild, nectar sugar concentrations are generally midrange, while volumes per bat are low, especially when many thirsty bats are competing for limited supplies.

    The article does not mention the climate in which these observations were made, or details of the bat experiments which identified the preference for more concentrated nectar.

    The word “thirst” could be a clue! I would imagine that bats on their Northbound migration feeding on Saguaro flowers in the Sonoran Desert, probably want water as well as nectar.

    The Weber-Fechner law dictates that the bats perceive increases in volume more acutely than they do increases in sugar concentration. In other words, they are more sensitive to changes in quantity than in quality.

    This could well be so, but sources of sugar and water would be relevant.
    Thirsty bats without access to open water, could well prefer watery nectar in quantity.
    I would suspect results from forest environments would be different to desert environments.

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