Biology Reference
In-Depth Information
(a)
(b)
(c)
Fig. 14.2
Stages of a fight between two red deer stags. The harem holder roars at the challenger (a). Then the
pair engage in a parallel walk (b). Finally they interlock antlers and push against each other (c). Photos by Tim
Clutton-Brock.
chance that even the winner may get injured. The important point is that these escalated
fights are rare and most contests are settled at an earlier stage by displays.
This raises the question of why individuals do not exaggerate their fighting ability in
displays such as roars and parallel walks to make even stronger individuals back down?
In this section, we will consider two examples in detail, toads and red deer, where the
answer is that fighting ability cannot be exaggerated, so the displays are honest signals
because they are indices.
Cues of fighting
ability are often
reliable because
they are indices
Fighting assessment and deep croaks in toads
The croak of the common toad,
Bufo bufo,
may provide an index of size and fighting
ability. Each spring, toads mass together in ponds to breed, with all spawning taking place
in one to two weeks. Females only visit the pond for a small number of days, so there are
always substantially more males than females, leading to intense competition for mates.
In the field, males would sometimes attempt to dislodge mating males from the back of a
female, by pushing in between the copulating pair. These takeover attempts were more
likely to be successful when the interrupting male was larger than the paired male, and
most takeover attempts involved a larger male trying to dislodge a smaller male.
Male toads
displace smaller
males
