Friday, March 31, 2017

How do Bats find Water?

A large part of an animal’s capacity to survive is its ability find resources. Each species of animal develops unique strategies for finding resources that permit them to survive and reproduce. For bats, the identification of water bodies is crucial to their survival and navigation. Ponds, lakes, and rivers provide an ideal habitat for bats as mating, breeding, and drinking grounds. Two researchers: Stefan Greif & Björn M. Siemers hypothesized the main strategy that echolocating bats used to find bodies of water is their echolocation. Because bodies of water generally have large smooth horizontal surfaces the researchers predicted that water acts as acoustic mirror; reflecting most of the energy in the echolocating calls back to the bats.

The bats collected for the experiment were presented two plates, smooth or textured made of the same material. The three types of material used were, metal, wood, and plastic. After each trial the bats were also presented water to determine their motivation for drinking. 15 different species of bats were tested in total. 

To determine how much dominance water like echoacoustic cues took dominance over behavior, a sooth metal was put under a table. The bats still tried to drink from the metal plate under the table. Based on the rationale bats use to find water this meant they were drinking water under another body of water. It seems the water like echoacoustic cues of the metal plate took dominance even with conflicting information. 
Echo signatures of natural and experimental surfaces.

A few variations of the experiment were conducted to confirm to different things about echolocating bats. The initial experiment was conducted on Juvenile bats who had never experienced a pond or rivers before. The juvenile bats showed identical drinking behavior for smooth plates as they did with water. To test conflicting sensory stimuli the experiment was also conducted in the dark. In the dark the bats had more drinking attempts for the metal plate than with the lights on. 

At the end of the experiment the hypothesis initially proposed by the researchers were confirmed. The echoacoustic cues of smooth plats were mistaken by bats as bodies of water. This was displayed through the bats’ attempts to drink the metal, wooden, and plastic plates. In each variation of the experiment the bats were consistent in their choice of the smooth plats over the textured plates. The smooth plates did in fact give of echoacoustic signals identical to water because they had smooth uniform surfaces which returned echoes identical to water. The results suggest information received through echolocation takes dominance over other sensory information. Even when the bats could see the plates weren’t water they still tried to drink them. The juvenile bats tested with no experience locating water still demonstrated preferential drinking behavior for smooth plates opposed to textured plats. This finding suggested the strategy for detecting bodies of water by echolocating bats is an innate ability. The juvenile bats never had the opportunity to learn this water locating strategy but they still used it.  

The foresight and efficiency Greif & Siemers conducted their experiment with is astonishing. They were able to validate two hypotheses with high certainty. These findings contextualize some bizarre behaviors of bats; like their affinity for car hoods and attics. The smooth surfaces of car hoods and rooftops could be attracting bats who perceive these inanimate objects as bodies of water. Based on the findings presented by the experimenters, efforts can be made to divert bats away from residential areas by incorporating more textured suffices into urban/residential design. 

Source: http://www.nature.com/articles/ncomms1110

Posted by: Michael Aflakpui group A

11 comments:

  1. Interesting read! I am currently taking mammalogy and we just learnt about bats and their echolocation adaptations and one that stuck out to me was the fishing bat (Noctilionidae Mystacinidae) and our professor was extensively discussing how efficient these bats' echolocation abilities are! She had said they could echolocate (while flying) and detect fish under the water that were swimming to the surface to snatch bugs, but then these bats swoop in and grab the fish.

    Posted by: Hargun Khanna

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    2. It is very interesting how bat Noctilionidae Mystacinidae can adapt their echolocation for fishing. I wonder if this ability is possible because these species are able to amplify their echolocation in some saw. I wonder if amplification would be achieved by dedicating more neurons to processing of sensory information or by increase the frequency of calls bombarding the water

      Posted by Michael Aflakpui

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  2. You did a great job of fully explaining this article. Bats are such interesting creatures and it's so crazy to me that they use echolocation so efficiently but still make mistakes like the ones explained here. This is a very important discovery that can help people make changes in order to conserve bats.
    Posted by Hannah Jordan group B

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    1. I agree, understanding bats more will help conservation efforts. Just like bees, we need bats to maintain balance in our ecosystem.

      Posted by Michael Aflakpui

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  3. For humans, finding water is easy. So, naturally, I never thought much about how other animals, like bats, may find water. You explained the information very thoroughly and in an efficient way which made it very easy to interpret. The use of echocaustic cues to find water is a very interesting method. It makes sense that the smooth metal was favored over the textured surfaces because water tends to be flat.

    Anna Potorski

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    1. True, we often put little thought into the lower levels of stimulus processing. I wonder how bats experience the world. We use special technology to make sense of what they do naturally but that doesn't bring us much closer to what it is like to be a bat. Most people aren't aware of the way our brains process boundaries, gradients, textures, shadows, and colors to inform our perception but these are the lower levels which build up to what we know in our environment. It would be cool to know what this picture looks like in the mind of a bat.

      Posted by Michael Aflakpui

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  4. I think this was a very interesting and efficient study done by Stefan Greif & Björn M. Siemers. As you mentioned, they definitely validated their hypotheses with certainty. It's interesting to see from this study just how much bats depend on their echolocation over their other senses. It is also very fascinating to sort of get to see how they use their echolocation with the smooth plates and the echo-acoustic cues from them.

    Posted by Jordan Milone (C)

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    1. Yes it is very cool to think about how other animals process their environment. I also wonder how helpless a bat would be without their echolocation.

      Posted by Michael Aflakpui

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  5. I have always been fascinated with bats! They are such a cool and unique species. I think it's amazing how they use echolocation to detect their prey as well as other resources, such as water, in the environment around them. I know bats can see almost as well as humans so I'm curious whether these experiments were done with the lights on or off and also if one sensory strategy takes prior over the other?

    Posted by: Katie Kossack (Group B)

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    1. There were trials with the lights on and trials with the lights off. Echolocation seems to take prior over other sensory strategies.

      Posted by Michael Aflakpui

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