First published online March 12, 2009
Journal of Experimental Biology 212, 901-905 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.024539
Local and global navigational coordinate systems in desert ants
Matthew Collett1,* and
Thomas S. Collett2
1 Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS,
UK
2 School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG,
UK
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Fig. 1. Food-ward trajectories. (A) The training route. F, feeder; N, nest; T,
tray. (B) Forager trajectories from the end of the barrier during training.
(C) Trajectories with the feeder and feeder landmark removed. Grid lines are
spaced at 1 m.
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Fig. 2. Food-ward and homeward trajectories. (A) Ants that have walked the full 10
m along the barrier. Food-ward trajectories are shown in green. Subsequent
homeward trajectories were recorded on a test ground, but are shown here
starting slightly displaced from the endpoints of the food-ward trajectories,
in black. The mean endpoint of the trajectories is indicated by a square.
Crosses indicate the standard errors. The position of the fictive nest would
be at (–1,2). (B) Ants that were carried for the first 4 m along the
route before being released. The position of the fictive nest would be at
(3,2).
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Fig. 3. Course setting using global coordinates. (A) After having travelled from
the nest at O to the current position at C, a forager makes a comparison to
reach the goal at G. The circles around C and G schematize the variation in
the global coordinates resulting from noise in PI. The four dashed lines
illustrate the range of possible variation in direction and distance of the
output from the comparison. The greater the distance travelled from O, the
larger the circles will be. The closer C and G are together, the greater is
the scatter in the output directions. (B) Model of the production and use of a
PI output vector coordinate system. An initiation comparison between current
global coordinates and the global coordinates of a goal produces the three
components of an output vector: a directional output command, an output
coordinate system and an output goal. As an ant moves, there are then further
comparisons (occurring within the shaded box) between the output coordinates
and the output goal.
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Fig. 4. Three possible relationships between the global and the output coordinates.
Integrators are indicated by shading in the boxes. (A) Each coordinate system
has its own integrator, each with input from a compass and odometer. (B) Only
the global coordinate system has an integrator. The output coordinates could
then be produced from the global integrator by using a memory of the global
integrator state on initiating the output vector: current output coordinates =
(initialization PI – current PI). (C) An output vector integrator
receives input from an odometer and compass. Every time a new output vector is
generated, the old output coordinates are added to a global integrator. The
global integrator then would not have direct input from a compass and
odometer, but only occasional input from the output vector integrator.
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© The Company of Biologists Ltd 2009
