Baum, W. M., & Kraft, J. R. (1998).
Group choice: Competition, travel, and the ideal free distribution.
Journal of the Experimental Analysis of Behavior,
69, 227-245.
If a group of foragers distributes among resource patches
according to the ideal free distribution, the relative number of
foragers in each patch should match the relative amount of
resource obtained there, unless deviations arise from factors
such as incomplete information or interforager interference. In
analogy to individual choice, such effects may produce
undermatching - group distribution falling short of resource
distribution - or overmatching - group distribution overshooting
resource distribution. In the present experiments, a flock of
about 30 pigeons distributed between two patches with continuous
inputs of green peas. Competition was varied by changing the size
or extent of the patches. When the patches were areas or troughs,
some undermatching occurred. When the patches were small bowls,
strong undermatching occurred. When travel was required to switch
patches, undermatching decreased slightly. A visual barrier that
prevented pigeons from seeing one patch from the other had no
effect. Overall rate of food delivery, varied over a wide range,
had no effect. It appeared that the mechanism of flock
distribution depended on comparisons between patches that were
successive rather than simultaneous. Although most pigeons
participated in the experiments, and different pigeons
participated to different extents, individual pigeons tended to
be consistent in the extent of participation from session to
session, suggesting the possibility that participation might
reflect competitive ability. Examination of the preferences and
switching of individual pigeons revealed no consistency within or
across individuals. It appeared that the flock's distribution was
a truly emergent phenomenon, in the sense that results at the
level of the flock in no way paralleled behavior at the level of
the individual.
The authors made video tapes showing pigeons foraging under
the three different conditions described in the abstract:
areas, troughs, or small bowls.
You can view three brief selections:
areas
troughs
small bowls
Each movie is approximately 2,500K.
For best viewing,
save a copy of each file to your own computer's desktop,
double-click on it
and then
change the image size in the player. Set the movie to "Loop"
if possible.
Lining up the three images horizontally and playing them
simultaneously is
most illuminating.
(See also JEAB's
Video Page.)
Key words: foraging, group choice, ideal free distribution,
matching law, competition, travel, pigeons