[Paleopsych] SW: Pigeon Homing and Highways

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Animal Cognition: Pigeon Homing and Highways

    The following points are made by H-P. Lipp et al (Current Biology 2004
    1) The most widely accepted explanation for pigeon homing over
    distances of 20 km and more is that they rely on a "map-and-compass"
    strategy. It has remained undisputed that pigeons have an internal
    clock and an internal sense of compass direction home and that this
    latter sense depends on the position of the sun, if visible. Yet
    directional knowledge alone is not sufficient for successful homing,
    and so pigeons must also have a large-scale mental map containing
    information about their current position with regard to their loft
    2) Mechanisms of position determination and the nature of the mental
    map used by homing pigeons have remained controversial for decades.
    Supporters of the magnetic theory of pigeon homing claim a predominant
    role of the earth's magnetic field for both compass and map mechanisms
    [2]. Others propose a major role of the olfactory system and
    atmospheric gradients [3,4]. Although vision is helpful yet not
    mandatory for successful long-distance homing [5], there is general
    agreement that pigeons rely at least partially on visual cues for
    flights within their familiar home range, 2-4 km around the loft.
    Whether the local visual information is used by the birds for homing
    from distant release sites -- a strategy coined "pilotage" -- has been
    equally controversial [2].
    3) Likewise, the nature of the objects used by pigeons for pilotage
    has been debated. Breeders of racing pigeons have often observed that
    large flocks of homing pigeons fly along major highways, and it is a
    familiar observation for most pigeon breeders that the birds often do
    not approach the home loft according to a straight compass direction
    from the release site. Early attempts to identify topographic
    guide-rails used by homing pigeons (e.g., roads, railways, powerlines)
    by means of airplane tracking have yielded equivocal results. Some
    studies reported positive evidence; helicopter tracking studies even
    found that pigeons were circling over road crossings. However, even in
    these positive cases, observations were rare and anecdotal.
    4) The authors present an analysis of 216 GPS-recorded pigeon tracks
    over distances up to 50 km. Experienced pigeons released from familiar
    sites during 3 years around Rome, Italy, were significantly attracted
    to highways and a railway track running toward home, in many cases
    without anything forcing them to follow such guide-rails. Birds often
    broke off from the highways when these veered away from home, but many
    continued their flight along the highway until a major junction, even
    when the detour added substantially to their journey. The degree of
    road following increased with repeated releases but not flight length.
    Significant road following (in 40%-50% of the tracks) was mainly
    observed from release sites along northwest-southeast axis.
    5) The authors suggest their data demonstrate the existence of a
    learned road-following homing strategy of pigeons and the use of
    particular topographical points for final navigation to the loft.
    Apparently, the better-directed early stages of the flight compensated
    the added final detour. During early and middle stages of the flight,
    following large and distinct roads is likely to reflect stabilization
    of a compass course rather than the presence of a mental roadmap. A
    cognitive (roadmap) component manifested by repeated crossing of
    preferred topographical points, including highway exits, is more
    likely when pigeons approach the loft area. However, it might only be
    expected in pigeons raised in an area characterized by navigationally
    relevant highway systems.
    References (abridged):
    1. Gould, J.L. (2004). Animal navigation. Curr. Biol. 14, R221-R224
    2. Wiltschko, R. and Wiltschko, W. (2003). Avian navigation: from
    historical to modern concepts. Anim. Behav. 65, 257-272
    3. Papi, F. (1990). Olfactory navigation in birds. Experientia 46,
    4. Wallraff, H.G. (2004). Avian olfactory navigation: its empirical
    foundation and conceptual state. Anim. Behav. 67, 189-204
    5. Schmidt-Koenig, K. and Schlichte, H.-J. (1972). Homing in pigeon
    with impaired vision. Proc. Natl. Acad. Sci. USA 69, 2446-2447
    Current Biology http://www.current-biology.com
    Related Material:
    The following points are made by C.V. Mora et al (Nature 2004
    1) Two conflicting hypotheses compete to explain how a homing pigeon
    can return to its loft over great distances. One proposes the use of
    atmospheric odors[1] and the other the Earth's magnetic field[2-4] in
    the "map" step of the "map and compass" hypothesis of pigeon
    homing[5]. Although magnetic effects on pigeon orientation provide
    indirect evidence for a magnetic "map", numerous conditioning
    experiments have failed to demonstrate reproducible responses to
    magnetic fields by pigeons. This has led to suggestions that homing
    pigeons and other birds have no useful sensitivity to the Earth's
    magnetic field.
    2) The authors made a series of modifications to an existing operant
    conditioning procedure to fulfill two conditions that seem to be vital
    for magnetic discrimination learning in non-avian species. These are
    that (1) the magnetic stimulus discriminated is a localized,
    non-uniform magnetic anomaly superimposed on the uniform background
    field of the Earth, and (2) movement by the experimental subjects is
    necessary to produce the behavioral response measured in the
    experiments. Although this combination of experimental parameters
    mitigates against rapid achievement of powerful discrimination by
    separating the stimulus, response and reinforcement in both space and
    time --compared with standard key-pecking experiments -- failure to
    fulfill either or both of the above conditions has characterized all
    the unsuccessful or irreproducible attempts to condition pigeons and
    many other species to magnetic fields.
    3) Using a Yes-No signal-detection procedure, four individually
    trained pigeons were required to discriminate between the presence and
    absence of an induced magnetic field anomaly while freely walking in a
    wooden tunnel. The intensity profile of the anomaly was "wave-shaped"
    and peaked in the center of the tunnel at 189 micro tesla (microT)
    (background level of 44 microT) with an inclination of -80 deg
    (background level of -64 deg). The birds were conditioned to jump onto
    a platform at one end of the tunnel when the anomaly was present and
    onto an identical platform at the other end of the tunnel when the
    anomaly was absent. Choice of the correct platform was rewarded with
    food whereas incorrect choices were punished with a time penalty.
    4) In summary: The authors demonstrate that homing pigeons (Columba
    livia) can discriminate between the presence and absence of a magnetic
    anomaly in a conditioned choice experiment. This discrimination is
    impaired by attachment of a magnet to the cere (part of the beak),
    local anaesthesia of the upper beak area, and bilateral section of the
    ophthalmic branch of the trigeminal nerve, but not of the olfactory
    nerve. These results suggest that magnetoreception (probably
    magnetite-based) occurs in the upper beak area of the pigeon.
    Traditional methods of rendering pigeons anosmic might therefore cause
    simultaneous impairment of magnetoreception so that future orientation
    experiments will require independent evaluation of the pigeon's
    magnetic and olfactory systems.
    References (abridged):
    1. Papi, F., Fiore, L., Fiaschi, V. & Benvenuti, S. Olfaction and
    homing in pigeons. Monit. Zool. Ital. (N.S.) 6, 85-95 (1972)
    2. Gould, J. L. The case for magnetic sensitivity in birds and bees
    (such as it is). Am. Sci. 68, 256-267 (1980)
    3. Moore, B. R. Is the homing pigeon's map geomagnetic? Nature 285,
    69-70 (1980)
    4. Walcott, C. Magnetic orientation in homing pigeons. IEEE Trans.
    Magnet. 16, 1008-1013 (1980)
    5. Kramer, G. Wird die Sonnenhöhe bei der Heimfindeorientierung
    verwertet? J. Ornithol. 94, 201-219 (1953)
    Nature http://www.nature.com/nature
    Related Material:
    Notes by ScienceWeek:
    An enormous variety of what are essentially experiments in viability
    has occurred during the more than 3.5 billion years of biological
    evolution on Earth, and among these experiments is a striking
    diversity of biological devices that function to sense changes in the
    environment of the organism. Consider, for example, magnetic field
    The following points are made by C.E. Diebel et al (Nature 2000
    1) The key behavioral, physiological, and anatomical components of a
    magnetite-based magnetic sense have been previously demonstrated in
    rainbow trout (Oncorynchus mykiss), with candidate receptor cells
    located within a discrete sub-layer of the olfactory tissues
    (olfactory lamellae) in the nose of the trout. These receptor cells
    were shown to contain iron-rich crystals similar in size and shape to
    magnetite crystals extracted from salmon.
    2) The authors now demonstrate that these crystals, mapped to
    individual receptors by *confocal and atomic force microscopy, are
    magnetic: the crystals are uniquely associated with dipoles detected
    by *magnetic force microscopy. Analysis of their magnetic properties
    identifies the crystals as *single-domain magnetite particles. In
    addition, 3-dimensional reconstruction of the candidate receptors
    using confocal and atomic microscopy imaging confirm that several
    magnetite crystals are arranged in a chain of approximately 1 micron
    length within the receptor, and that the receptor is a multi-lobed
    single cell.
    3) The authors suggest these results are consistent with a
    magnetite-based detection mechanism, since 1-micron chains of
    single-domain magnetite crystals are highly suitable for the
    behavioral and physiological responses to magnetic intensity
    previously reported for the trout.
    4) The authors conclude that "understanding should now be sought of
    how the chains of crystals could transduce a magnetic field into an
    electrical signal in the nervous system."
    Nature http://www.nature.com/nature
    Notes by ScienceWeek:
    confocal and atomic force microscopy: In general, a "confocal
    microscope" is a microscope in which an aperture in the illuminating
    system confines the illumination to a small spot on the specimen, and
    a corresponding aperture in the imaging system (which may be the same
    aperture in reflecting and fluorescence devices) allows only light
    transmitted, reflected, or emitted by the same spot to contribute to
    the image. By suitable mechanical or optical means, the spots are made
    to scan the specimen as in a television raster. Compared to
    conventional microscopy, confocal techniques offer improved resolution
    and improved rejection of out-of-focus noise. In atomic force
    microscopy, a tip is fixed to a cantilever whose position is monitored
    while the tip scans the surface. The force between the tip and the
    surface determines the position of the cantilever. When recorded in
    atomic resolution, the image represents a map of atomic forces at the
    surface. The advantage of atomic force microscopy is that the probed
    surface does not need to be electrically conducting.
    magnetic force microscopy: This technique is capable of determining
    magnetic domain structure in a variety of magnetic materials,
    including small particles with a spatial resolution of less than 100
    nanometers. Because it is sensitive to magnetic forces, the technique
    can also image magnetic structures that are covered by a layer of
    non-magnetic material.
    single-domain magnetite particles: An oxide of iron, magnetite
    (magnetic iron ore) is attracted by a magnet but does not attract
    particles of iron to itself. In this context, the term "domain" refers
    to a region in which magnetic moments are uniformly arrayed.

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