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Science

An Alligator's Sixth Sense 31

Posted by michael from the slow-tourist dept.
Devil's BSD writes "NPR has this article about how alligators sense their prey. Apparently, those black dots on a alligator are really "dome pressure receptors", which alligators use to detect changes in water pressure caused by ripples in the water. The alligator then does some fancy triangulation, and can then detect precisely where its prey is."
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An Alligator's Sixth Sense More

An Alligator's Sixth Sense

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  • http://www.wam.umd.edu/~daph/DPR.html [umd.edu]
    They have some movies in .qt format showing the gators attacking drops of water.

  • Sixth Sense? (Score:3, Funny)

    by alnapp ( 321260 ) on Thursday May 16, 2002 @09:43AM (#3529370) Homepage
    I see Handbags, all the time

  • Hogwash (Score:1, Funny)

    by PhysicsGenius ( 565228 )
    The reptile brain is far to unsophisticated to be able to handle counting, let alone trigonometry. Please, Slashdot, apply a little common sense before posting these ridiculous claims.

    • Not Hogwash (Score:5, Insightful)

      by crow ( 16139 ) on Thursday May 16, 2002 @10:34AM (#3529671) Homepage Journal
      It's not hogwash at all. Sure, reptile brains may be simple in many ways, but that's not relevant. You don't have to be able to perform advanced trigonometry and calculus to figure out the trajectory of a thrown ball so that you can catch it. Instead, you get a sense for where the ball is going based on having seen balls thrown before.

      Likewise, the alligator simply notices that certain patterns of pressure changes indicate that there is something in the water in a given direction.

      Sure, you can describe what is going on with advanced mathematics, but the actual application is done with simple pattern matching.
      • Sure it is pattern matching ... but it is not sixth sense that the article seems to suggest (and what the poster was talking about)
  • My one question about this whole theory is what do the alligators do when it rains (other than get wet)? I imagine there must be some sort of way to cut down on the feedback/nerve responses. Also, when they swim, it seems that the pressure receptors would boggle the alligator.

    • Re:Boggled alligators (Score:4, Informative)

      by Nos. ( 179609 ) <andrewNO@SPAMthekerrs.ca> on Thursday May 16, 2002 @03:09PM (#3532045) Homepage
      The article I read a day or two ago (on CBC's website [www.cbc.ca] compared it to the human ear. Our ear works basically the same way as these sensors. When there's a lot of noise, it tends to be ignored, but you can still pick out differences. My guess would be that the first few drops may get the gator's attention, but after that it would become background "noise". However, an animal splashing around would proably make bigger waves, and thus be more noticeable.
  • I remember watching a show, probably on the Discovery Channel, about how many animals have weird senses. For example, some birds apparently see a spot at magnetic north and can use that for navigation. Turtles have some similar sense that they also use for navigation.

    And we all know bats use sonar.

    What other senses do animals have that we lack?

    • Re:Other senses (Score:2, Informative)

      by rusty0101 ( 565565 )
      Bees sense polarization of light, As a result the sky is their map.
    • Electric eels and some kinds of fish can detect movement
      within an electric field that they project around
      their bodies.
    • Oh, I almost forgot. Pit vipers have special organs (pits) that enable them to sense the heat of their prey.
    • most (if not all, i don't completely remember my ornithology class) birds have a "dip angle compass" in their heads. it's not really a dip angle compass, but they can feel the change. it tells them how far north or south they are in relation to the north (or south) poles. i do not think they see an actual spot at magnetic north, but they can feel it. and those that cross the equator during migration reverse their "compass" so that they know they are still flying either north or south. birds are actually pretty cool. they also see a whole different light spectrum than humans (but that is true for a lot of other animals). i think birds can see ultraviolet light.

      other mammals can detect non-volatile chemicals, such as pheromones, which humans are not completely known to detect. they have a vomero-nasal organ which is located just above the roof of the mouth. you can see little holes in the skull where the canal leads to it. humans lack this organ. you can see cats using it through flehman, which is what they do when you see them scrunch their noses and upper lips. they are actually pulling air into the vomero-nasal organ. other mammals use licking and nuzzling to get chemicals into this region.

      many animals are much cooler than people normally think, but that's because most people don't know much about them other than what they look like.

    • It is often suggested (a.o. on the Discovery Channel) that animals have superiour senses compared to humans. This statement is IMO a bit blunt; there is no such group as "the animals" compared to "the humans". One could as easily argue that the sense of animals (including humans) have a superiour sense to say, dogs.

      Instead some (or many) animals have senses which our superiour to ours but other senses which are less developed than ours. For example, apes are capable of 3D color vision, but nocturnal bats equipped with sonar barely use their eyes.

      Which is not to say that there are some very exciting sensory systems in the animal kingdom. There is a great variety in sensory systems over in animals. But I think that a more proper way to look at that is by understanding why an animal posesses such an organ in relation to its life-style, instead of just saying "animals" are better equipped than "humans".

  • Ears? (Score:2)

    by zpengo ( 99887 )
    Apparently, those black dots on a alligator are really "dome pressure receptors", which alligators use to detect changes in water pressure caused by ripples in the water. The alligator then does some fancy triangulation, and can then detect precisely where its prey is."

    Perhaps I'm mistaken, but isn't that essentially what ears do?

    • Last time i checked that's what my ears do. Except you can't triangulate with only 2 points, but your brain uses other cues to determine where the sound is located.

      I'm curious about this "fancy triangulation" though. Does it use a graphing calculator or what?
      • Slide rule for the older crocs and younger crocs pull out a PDA and do the figures that way....
      • Except you can't triangulate with only 2 points,

        When was the last time you saw a triangle? The 2 points of your ears can tell you where the third point is. They're a little close together, and pointing in opposite directions, so they're less accurate than your eyes, but they still do a pretty good job.

        • well, lets go through an example together, ok?
          your left ear hears a sound that's 2 feet away. all points 2 feet away will make a sphere around this ear (with a radius of 2 feet).
          your left ear hears a sound 1 foot away. all points from this ear makes a sphere around it (with a radius of 1 foot).
          all points where these 2 spheres intersect form a circle.
          your brain uses many clues to locate the sound on this circle. two of the ways that it does this is if you move (by turning your head or whatever) or the sound moves. usually your brain just locates it from memory (certain sounds come from certain objects, certain voices come from certain people, etc.)
          when you think in three dimensions, it doesn't really look like a triangle. i'm not exactly an expert in this area (i did take psychology of perception in college), so feel free to prove me wrong. ;-)
  • Can you imagine a cluster of these? I have a feeling it would resemble the store window of an exotic accessory store: boots, bags, hat bands.... :)
  • University of Maryland doctoral student Daphne Soares holds the skull of a gator she calls "Sammy."

    So, she names the dead ones? Interesting.

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