Biology Reference
In-Depth Information
Females
Males
0.50
0.40
0.30
0.20
0.10
Without close
gen. rels in
home cot.
(type A)
With only
non-descendant
close gen. rels.
in home cot.
(type B)
With offspring
in home cot.
(type C)
Fig. 11.1
Alarm calling by black-tailed prairie dogs to a stuffed badger. For both males (dark blue histograms)
and females (light blue), there are significant differences between type A and type B individuals and also
between type A and type C. There was, however, no significant difference for either sex between type B and
type C. Data are means
±
1 SE. From Hoogland (1983). With permission of Elsevier. Photographs show a female
making an alarm call, and a stuffed badger that is pulled across ground to simulate the presence of a predator.
Both photos © Elaine Miller Bond.
offspring present. Factors other than the warning of relatives must also be involved,
however, because immigrants who had no relatives nearby nevertheless sometimes
called (Fig. 11.1). There may sometimes be direct benefits to the caller itself in giving
the alarm, for example signalling to the predator 'I've seen you', which may reduce the
likelihood of attack because the predator then does not have the advantage of surprise.
Another possibility is that it pays to warn others of the approach of a predator, even if
they are not close relatives, because if a neighbour was caught successfully then the
predator may be more likely to return to hunt in the same area again. Alarm calling,
may, therefore reduce the likelihood of future attacks by the same predator.
These studies of cooperation among relatives in ground squirrels and prairie dogs are
consistent with the kin selection model but they do not constitute a quantitative test of
Hamilton's rule. Indeed, it would be difficult to assess the costs and benefits of alarm
calls in terms of offspring lost and gained. We now turn to an example where these
values could be estimated.
… but also when
there are no
relatives nearby
Cooperative courtship in wild turkeys
In the wild turkey,
Meleagris gallopavo,
pairs of same aged males sometimes form
coalitions to court females, and then defend those females against other males
(Fig. 11.2). In these groups, one of the males appears to be dominant, obtaining all the
A quantitative
test of Hamilton's
rule
