Biology Reference
In-Depth Information
Image
Time
(weeks)
Fig. 12.6 The
amount of money
(pounds sterling)
paid per litre of
milk consumed as a
function of week
and the image
placed next to a
notice requesting
payment. From
Bateson et al .
(2006). With
permission of the
Royal Society.
Photograph shows
a crime prevention
poster produced by
the West Midlands
Police, UK,
following this
research. With
permission of the
West Midlands
Police.
10
9
8
Eye weeks
Flower weeks
7
6
5
4
3
2
1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
£ paid / litre milk consumed
(1) Sufficient repeated pairwise interactions, so that there is the possibility for individuals to
take turns helping each other . In the field it was found that some unrelated individuals
were constant companions in the roosts, sometimes for several years.
(2) The benefit of receiving aid must outweigh the cost of donating it . Fig. 12.7 shows that the
bats lost weight with increasing time since their last meal. The decelerating curve
means that a donation of a small amount of blood by a well-fed individual results in
little cost in terms of time moved along the bottom axis towards the threshold of
Vampire bats
share food with
both relatives and
non-relatives
Repeated
interactions occur
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