Bat Maps

Dr. Nachum Ulanovsky of the Weizmann Institute and Prof. Ran Nathan and Asaf Tsoar of the Hebrew University of Jerusalem have captured live fruit bats and glued tiny GPS transmitters to their backs, then driven the bats overnight to a site some 80 kilometers away and rappelled into the bats’ caves to retrieve the transmitters after they fall off – all in the name of scientific research. In the process, the team has revealed how these bats form mental maps that they use to return to their favorite fruit trees night after night, often flying large distances and bypassing other, similar trees on the way.

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Bats are famous users of hearing to navigate – finding their way around by echolocation. Echolocation is extremely useful for flitting around one’s immediate surroundings in the dark, but Ulanovsky and his collaborators suspected that the bats were making beelines for their trees using a different sense. Flying hundreds of meters up in the air at speeds of up to 60 km an hour, the bats appeared to rely on an internal, mental map of the territory below.

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To test the limits of that map, the researchers first took the bats outside their normal range and released them. Then, to hide any visual landmarks the bats may have been using to steer by, they drove them some 84 km away and released some of them from the bottom of a wide erosion crater and others from the top. The bats released from the crater’s rim made their way straight back home from the distant, unfamiliar departure point. Only those that found themselves inside the crater seemed to lose their bearings (and these regained them, once they reached the rim).

It turns out that the saying “blind as a bat” doesn’t really apply to these furry flying mammals. “Birds’-eye view” might be more like it: The bats apparently watch for prominent visual landmarks – light clusters, for instance, or hills – judge their distance and mentally triangulate their positions. Ulanovsky thinks that these masters of navigation may even have further means of plotting their positions, as a back-up for times when visibility is poor. These could include the ability to sense directional sea breezes or magnetic fields.

Ulanovsky is a neurobiologist; he carried out this research together with the team of ecologists from the Hebrew University, and with scientists in Italy and Switzerland. Their findings could shed light on both bat ecology and the ways that mammals – including humans – form mental maps of large areas.

See a bat’s eye view of its flight path

Comments

  1. #1 KevinH
    August 16, 2011

    pretty cool.

    It wasn’t quite clear form your summary and the article is gated. Did the bats go in all directions equally in the crater or were they biased towards home. That should give them an idea if its a visual or magnetic que.

    Also, do would the ‘survivor bias’ be present because they only got GPS tags from the bats that made it back? I guess you could also spin it as an internal control because they only got data from the bats that were successful in making it back.

  2. #2 Weizmann Science Writer
    August 16, 2011

    The bats at the bottom of the crater took flew in circles for quite a while before finding their way out, while those at the top flew back in a straight line. But when the ones in the crater did manage to exit, it was mainly from the north side, implying that they do use either directional breezes or magnetic cues, as a backup to sight. Since the team managed to recover something like 90% of the GPS devices, it is unlikely that these had any effect on the bat’s chances of returning.

  3. #3 James Liljenwall
    August 17, 2011

    Where do you get your GPS devices? (I need one equally small for a young tortoise.)

    How do you manage to get them to fall off only after the bats get back to the cave, as the article implies? In fact, why do they fall off at all?

  4. #4 haber
    August 18, 2011

    sadece sevdim

  5. #5 Weizmann Science Writer
    August 18, 2011

    The devices were specially designed for bat experiments. Not commercially available. They fall off because they are attached with surgical glue that degrades after a day or two.

  6. #6 haber
    August 21, 2011

    mükemmel resimler saol.

  7. #7 knightly
    August 22, 2011

    Na na na na na na na na na na na na na na na na BAT MAP!

  8. #8 Katy W
    October 2, 2011

    The phrase “blind as a bat” has been around for as long as I can remember. It’s interesting that according to this experiment, bats can navigate better than most humans I know. I wonder if their limited visual capability is offset or even made irrelevant by their ability to make these “mental maps” and their other senses (which might be stronger). I also wonder if we can learn anything from these bats that we can apply to our own navigational techniques.

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