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First published online October 21, 2005
Journal of Experimental Biology 208, 4005-4011 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01873

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Path integration in a three-dimensional maze: ground distance estimation keeps desert ants Cataglyphis fortis on course

Gunnar Grah¹, Rüdiger Wehner² and Bernhard Ronacher^1,*

¹ Department of Biology, Humboldt-Universität zu Berlin, Invalidenstrasse 43, D 10099 Berlin, Germany
² Department of Zoology, University of Zürich, Winterthurerstrasse 190, CH 8057 Zürich, Switzerland

View larger version (99K): [in a new window]   Fig. 1. Training situations. (A) Experimental set-up for 3D outbound runs. (B) Schematic view of 2D ground distance control. (C) Schematic view of 2D walking distance control.

View larger version (22K): [in a new window]   Fig. 2. Homebound paths of individual ants from their point of release, R, plotted for the first 30 s of each search run (N=27 in A, N=22 in B, N=21 in C). NG depicts the relative nest position according to ground distance in the 3D test (A) and ground distance control (B). NW is the relative nest position in walking distance controls (C). Square brackets in B and C indicate the predicted nest position of the other control group, respectively, and are shown for comparison.

View larger version (36K): [in a new window]   Fig. 3. Intersection points of homeward runs of different individuals of Cataglyphis fortis, at 1 m and 2 m radius from the release point. Long arrows depict vector strengths at the 2 m radius, where full radial length equals 1. Short arrows show the true vector to the nest in 3D tests and ground distance controls (black), walking distance controls (white), and straight controls (grey). (A) 3D outbound run (N=26 at 1 m, N=23 at 2 m radius); (B) ground distance control (N=22 at 1 m, N=20 at 2 m radius); (C) walking distance control (N=21, both radii); (D) straight control (N=20, both radii). Note that data points obscure others with identical azimuth.

View larger version (11K): [in a new window]   Fig. 4. Average distances covered before the ants start to search for the nest. Shown are the median, quartile range and extremes. Broken lines show the real distance of the nest.

View larger version (145K): [in a new window]   Fig. 5. Search density distributions of ants within the test area after different outbound runs (N=27 in A, N=22 in B, N=21 in C, N=20 in D). One pixel represents an area of 0.25 mx0.25 m. Densities are defined as the summed path lengths within one pixel, divided by the total path length for all pixels of each test situation. The obtained values for each pixel are colour-coded from black (minimal value; 0) to red (maximal value; 0.845 in A, 0.926 in B and C, 0.773 in D). R, point of release; NG depicts the relative nest position according to ground distance in the 3D test (A), ground distance control (B), and straight control (D). NW is the relative nest position in walking distance controls (C). Square brackets in B and C indicate the predicted nest position of the other control group, respectively, and are shown for comparison.