[Paleopsych] SW: On Ant Navigation

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Wed Oct 19 01:49:59 UTC 2005

Animal Behavior: On Ant Navigation

    The following points are made by Francis Ratnieks (Nature 2005
    1) There are probably 20,000 ant species and they do not all use the
    same navigational methods or have equal navigational abilities. Many
    can reorient on trails by using external cues, including landmarks and
    the position of the Sun. Leafcutter ants are even thought to use the
    Earth's magnetic field. But recent research has shown that one common
    ant, the pharaoh's ant, Monomorium pharaonis, has a sense of geometry,
    and other species probably do as well.
    2) A pharaoh's ant colony forms a foraging-trail network leading from
    the nest entrance into the surrounding environment. These trails form
    Y-shaped branches with an internal angle of approximately 60 degrees
    as they lead away from the entrance. Ants walking the wrong way along
    a trail are unable to reorient at a trail bifurcation if the angle is
    120 degrees. But if the angle is less, then they can. Angles less than
    120 degrees give the "Y" bifurcation a nest-environment polarity,
    whereas at 120 degrees there is only symmetry. The ability to reorient
    is maximized at the natural bifurcation angle of 60 degrees.
    3) Natural selection has made insect societies good at solving a
    problem that is simple to state but hard to solve -- to send foragers
    to where the food is. Because social insects have been solving this
    complex dynamic problem for millions of years, they have probably
    evolved some simple and elegant solutions. We should care about these
    solutions because human life depends more and more on engineering
    systems that must solve similar problems to function efficiently --
    electronic messaging, grid computing, transmitting electricity and
    traffic regulation to name a few. One obvious lesson we might learn is
    how to make our systems more reliable and robust. If there is one
    thing that natural selection should be good at, it is eliminating
    solutions that are not robust. The colony or organism that "crashes"
    will soon be a dead one.
    4) When a physicist plays ants at their own game -- trying to
    understand a problem fundamental to colony survival that ants have
    been working on, by means of natural selection, for millions of years
    -- ants can come out ahead. It is no disgrace to be outsmarted by
    ants. But are we smart enough to learn from them?[1-3]
    1. Feynman, R. P. Don't You Have Time To Think? (ed. Feynman, M.)
    (Allen Lane, 2005).
    2. Feynman, R. P. Surely you're joking, Mr. Feynman! (Norton, New
    York, 1985).
    3. Jackson, D. E., Holcombe, M., Ratnieks, F. L. W. Nature 432,
    907-909; 2004.
    Nature http://www.nature.com/nature
    Related Material:
    The following points are made by James L. Gould (Current Biology 2004
    1) Nearly all animals move in an oriented way, but navigation is
    something more: the directed movement toward a goal, as opposed to
    steering toward or away from, say, light or gravity. Navigation
    involves the neural processing of sensory inputs to determine a
    direction and perhaps distance. For instance, if a honey bee were to
    seek food south of its hive, it would depart from home with the sun to
    its left in the morning, but to its right in the afternoon.
    2) Several trends reflecting favorably on natural selection and poorly
    on human imagination characterized early studies of navigation. One
    tendency was the assumption that animals sense at most the same cues
    as we do. Thus, being blind to our own blindness, it came as a total
    surprise when honey bees and many other species were found to be able
    to see UV light. As navigation depends on the processing of such cues,
    the number of "new" senses uncovered in the past fifty years has
    greatly expanded our thinking about what may be going on in the minds
    of animals -- and there is no reason to assume the list is complete.
    To UV must be added polarized light, infra-red light, special odors
    (pheromones), magnetic fields, electric fields, ultrasonic sounds and
    infrasonic sounds.
    3) The second crippling propensity is what navigation pioneer Donald
    Griffin called our innate "simplicity filter": the desire to believe
    that animals do things in the least complex way possible. Experience,
    however, tells us that animals whose lives depend on accurate
    navigation are uniformly overengineered. Not only do they frequently
    wring more information out of the cues that surround them than we can,
    or use more exotic or weaker cues than we find conceivable, they
    usually come equipped with alternative strategies -- a series of
    backups between which they switch depending on which is providing the
    most reliable information.
    4) A honey bee, for instance, may set off for a goal using its
    time-compensated sun compass. When a cloud covers the sun, it may
    change to inferring the sun's position from UV patterns in the sky and
    opt a minute later for a map-like strategy when it encounters a
    distinctive landmark. Lastly, it may ignore all of these cues as it
    gets close enough to its goal to detect the odors or visual cues
    provided by the flowers. This is not to say that animals do not often
    rely on approximations and neural shortcuts to simplify these daunting
    5) A third stumbling block has been our presumption that because the
    earliest cases studied involved "imprinting" (irreversible one-trial
    learning), animals must have simple navigation programs, which need
    merely to be calibrated to the local contingencies. This is just what
    at least some relatively short-lived animals do -- like honey bees for
    instance, who rarely forage for more than three weeks. But most
    animals live longer, and in consequence many need to recalibrate
    6) Finally, most researchers deliberately ignored or denigrated the
    evidence for cognitive processing in navigating animals. This legacy
    of behaviorism (the school of psychology that denied instinct) puts a
    ceiling on the maximum level of mental activity subject to legitimate
    investigation. There are many navigating animals whose behavior lacks
    any hint of cognitive intervention. However, the obvious abilities of
    hunting spiders and honey bees to plan novel routes make it equally
    clear that phylogenetic distance to humans is no sure guide to the
    sophistication of a species' orientation strategies.(1-3)
    Able, K.P. and Able, M.A. (1995). Interactions in the flexible
    orientation system of a migratory bird. Nature 375, 230-232
    Gould, J.L. (1980). The case for magnetic-field sensitivity in birds
    and bees. Am. Sci. 68, 256-267
    Walker, M.M. (1998). On a wing and a vector. J. Theor. Biol. 192,
    Current Biology http://www.current-biology.com
    Related Material:
    The following points are made by M.V. Srinivasan (Current Biology 2003
    1) Many of us have marvelled at the ability of honeybees to find an
    attractive flower patch, miles away from their hive, and to return to
    it repeatedly with unerring accuracy. How do they do this with a brain
    smaller than a sesame seed? We don't know all the answers yet, but
    bees seem to be able to estimate the distance to a food source, gauge
    the direction in which to fly to reach it, and convey this information
    to their nestmates, so that they can forage from it, too, and thus
    collectively build up the colony's food reserves.
    2) It appears that bees use one or both of the following cues. The
    first comes from measuring the amount of energy consumed when they fly
    to the destination by the reduction in the volume of their
    nectar-laden stomachs; the greater the energy consumed, the further
    the distance. And the second comes from measuring how much the image
    of the world appears to move in the eye as they fly to the
    destination; the greater the extent of image motion, the further the
    3) Bees use the Sun as a compass. Even if the Sun is hidden by a
    cloud, bees can continue to steer correctly by inferring the Sun's
    position from the pattern of polarized light that it creates in a
    patch of clear sky. This polarized-light pattern is visible to them
    but not to us, unless we view the sky through polaroid sunglasses.
    Bees are also able to compensate for the daily movement of the Sun
    across the sky by using information from an internal biological clock.
    4) A "scout" bee recruits her nestmates to visit a newly discovered
    flower patch. Upon returning to the hive, the scout performs a
    "waggle" dance on the vertical surface of the honeycomb. This dance
    consists of a series of alternating left-hand and right-hand loops,
    interspersed by a segment in which she waggles her abdomen from side
    to side. The duration of this waggle phase is a measure of the
    distance to the food, and the angle between the axis of this waggle
    segment and the vertical represents the azimuthal angle between the
    sun and the direction in which the recruit should fly to find the
    target. Thus, the dance conveys the position of the food source
    relative to the hive in polar coordinates.
    5) A bee that has visited a promising flower patch a few times will
    rapidly learn the color, shape and fragrance of the flowers, and use
    these cues to home in on them on return visits. Bees have excellent
    trichromatic color vision, featuring three types of photoreceptor
    which are maximally sensitive to the ultraviolet, blue and green
    wavelengths of light, respectively. Honeybees rival humans in their
    ability to discriminate subtle color differences. Bees that repeatedly
    visit a given flower patch also learn to use prominent landmarks, if
    there are any present, as navigational aids. For example, a landmark
    could be used as a beacon that guides that bee toward her destination.
    Landmarks can also function as checkpoints along the route. Thus a bee
    can learn, for example, that the shortest route to the goal is to fly
    to the left of landmark A, and to the right of landmark B. There is
    also some evidence that bees can "count" prominent landmarks that they
    encounter en route to the food. Finally, honeybees probably use
    memorized visual "snapshots" of the surrounding environment at the
    destination to help them to return to the same spot repeatedly and
    1. Collett, T.S. and Zeil, J. (1998). In Spatial representation in
    animals. In Healy, S. ed. (Oxford University Press), pp. 18-53
    2. Srinivasan, M.V., Zhang, S.W., Altwein, M., and Tautz, J. (2000).
    Honeybee navigation: nature and calibration of the "odometer". Science
    287, 851-853
    3. von Frisch, K. (1993). The Dance Language and Orientation of Bees.
    (London: Harvard Univ. Press)
    4. Wehner, R., Michel, B., and Antonsen, P. (1996). Visual navigation
    in insects: Coupling of egocentric and geocentric information. J. Exp.
    Biol 199, 129-140
    Current Biology http://www.current-biology.com

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