Biology Reference
In-Depth Information
(a)
i
ii
(c)
(b)
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
Domain of danger (m
2
)
Fig. 6.4
(a) W.D. Hamilton's (1971) model of the selfish herd. Each frog has a 'domain of danger' in which it is
likely to be selected for attack if a predator appears: this is shown for one individual in (i) as the solid bar, and is
the zone stretching half way to the neighbour on either side. Any predator approaching this zone will select this
frog as the nearest potential victim. The frog can reduce its zone of danger by jumping to settle in between two
closer neighbours (arrowed movement, new domain of danger shown by dashed line). If all frogs follow this
principle, the result will be increased aggregation (ii). (b) A test of Hamilton's model. An experiment with groups
of decoy styrofoam seals, attached to a raft using reed poles, and then presented to great white sharks (see
text). A shark attacking the decoys. Photo © Claudio Velasquez Rojas/Homebrew Films. (c) An individual seal
decoy's risk of shark attack increased with its domain of danger, as assumed in Hamilton's model. De Vos and
O'Riain (2010).
