A while back Allen Dick asked for an experiment which could falsify
bee dance communication. If an experiment could be designed which
could provide evidence that the bees don't use the information in the
dance, that would blow a big hole in the idea.

Well, it appears that the following study does that: it tests what
happens if the bee dance is scrambled so that the bees can't really
use it to find food sources. Does it make a difference? The answer may
surprise you. It depends.  (The title is funny too...)

* * *

Honeybee colonies achieve fitness through dancing
Gavin Sherman & P. Kirk Visscher
Department of Entomology,
University of California,
Riverside, California 92521, USA

EXCERPTS:

The honeybee dance language, in which foragers perform dances
containing information about the distance and direction to food
sources, is the quintessential example of symbolic communication in
non-primates. The dance language has been the subject of controversy,
and of extensive research into the mechanisms of acquiring, decoding
and evaluating the information in the dance. The dance language has
been hypothesized, but not shown, to increase colony food collection.
Here we show that colonies with disoriented dances (lacking direction
information) recruit less effectively to syrup feeders than do
colonies with oriented dances.

For colonies foraging at natural sources, the direction information
sometimes increases food collected, but at other times it makes no
difference. The food-location information in the dance is presumably
important when food sources are hard to find, variable in richness and
ephemeral. Recruitment based simply on arousal of foragers and
communication of floral odour, as occurs in honeybees, bumble bees and
some stingless bees, can be equally effective under other
circumstances. Clarifying the condition-dependent payoffs of the dance
language provides new insight into its function in honeybee ecology.

After honeybee dances were first decoded by von Frisch, controversy
arose about whether bees that follow dances actually decode the
distance and direction information, or instead rely exclusively on
odour. Subsequent experiments established that bees can decode the
dances, but the relative role of odour and vector information has been
little studied. Mechanistic and descriptive studies suggest that the
dance makes the nest an information centre where communication allows
a colony to direct most of its foragers to the richest sources found,
increasing the colony food collection, but this hypothesis has not
been effectively tested.

To test the effect of the dance language, we established a diffuse
light treatment in which bees performed completely disoriented dances,
and an oriented-light treatment in which bees performed well-oriented
dances.

Former studies comparing disoriented and oriented dances compared
vertical and horizontal hives, which may differ in factors other than
dance orientation. We used two frame horizontal observation hives that
could be illuminated with either treatment: light from three 25-W
bulbs diffused through white translucent Plexiglas suspended above the
colony, or unidirectional light from one 75-W bulb above a sheet of
transparent Plexiglas plus a fluorescent 'black light' providing short
wavelengths.

The results demonstrate that under natural foraging conditions the
communication of distance and direction in the dance language can
increase the food collection of honeybee colonies. They also robustly
confirm that bees use this directional information in locating the
food sources advertised in the dance.

However, the study also demonstrates that this advantage does not
always hold. In the feeder-recruitment experiments, dance-language
vector information increased the number of recruits that found the
feeders, but about one-third as many recruits came even without
directional information, presumably relying on learning the scent of
the feeder from the dancing bees and then searching for that scent in
the field. During summer and autumn, there was no significant
difference in the food collected, as measured by mass changes, when
colonies did and did not have directional information from the dance.

However, in conditions like those in winter in this study,
communication of food source location does increase a colony's food
intake. We note that this difference does not just reflect food
abundance. The seasons (summer and autumn) in which oriented dancing
was not associated with greater food gain had average mass gains that
were greater (summer) and less (autumn) than the season (winter) in
which oriented dancing did lead to greater food collection.

(c) 2002 Nature Publishing Group
NATURE | VOL 419 | 31 OCTOBER 2002
www.nature.com/nature


-- 
Peter Borst

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