Biology Reference
In-Depth Information
there was no variation with lek size in the number of females attracted per male. In the
other species, larger leks (18-36 males) did attract more females per male than smaller
leks (six males), but curiously leks in this species tend to be small, not large.
Males aggregate around attractive 'hotshot' males
Average
success per male may not be what we really need to measure because individuals
may vary in their ability to signal. If some males had particularly effective displays
('hotshots'), it could pay poorer signallers to cluster around them to parasitize their
attractiveness (Beehler & Foster, 1988).
This process certainly seems to explain male aggregation on a small scale, such as that
involving calling and satellite male toads (Chapter 5), but two sources of evidence suggest
that it cannot explain the larger scale aggregations of leks. Firstly, when the most
successful males are removed from a lek, their territories are quickly taken-over by other
males (sharp-tailed grouse, Rippin & Boag, 1974; white-bearded manakins, Lill, 1974).
This suggests that there is something about the site which influences female preference.
The 'hotshot model' predicts that the next most preferred male would remain on his
territory with the male aggregation rearranging around him, rather than for replacement
to occur on particular sites. Secondly, in an experiment on fallow deer (
Dama dama
) leks,
Clutton-Brock
et al
. (1989) covered the territories of the most successful males with
black polythene, so forcing them to change site. Even though these males set up new
territories several hundred metres away, they remained favoured by females. In this case,
therefore, females were apparently choosing particular males rather than particular
sites. The hotshot model predicts that the other males should have followed the
movements of these attractive males to set up a lek at the new site. However, most
remained on their old territories. Thus, the hotshot model may not explain male
aggregation on leks even when females are choosing males rather than particular sites.
Poorer signallers
may parasitize
better signallers
Females prefer male aggregations because these facilitate
mate choice
Although lek mating systems are rare, they have attracted considerable attention
because of the fact that females seem to exercise careful choice before they mate, with
particular males gaining most of the matings. Because males of lekking species do not
provide any parental care, the only possible gains from such choice are either a safe
mating (safety from male harassment or predation) or genetic benefits (Chapter 7). It is
still not clear whether one or both of these benefits is important. For example, female
black grouse (
Lyrurus tetrix
) prefer the males with the most vigorous displays and these
chosen males also have higher survival (Alatalo
et al
., 1991). One possibility, therefore,
is that leks provide a testing ground where males reveal their health and viability
through the vigour of their displays; if there is any heritability of male viability then
females will gain good genes for their offspring by mating with the most vigorous males.
Thus, female choice may lead to male aggregations either because choice of a particular
site enables females to gain matings with the most vigorous male (the one able to win
that site), or because preference for aggregations facilitates comparison among males.
In conclusion, the factors leading to lek mating systems are likely to be diverse. All five
hypotheses may be important, with different explanations applying to different species
or at different spatial scales.
Do females
choose males
directly or
particular sites on
a lek?
Female choice
may bring genetic
benefits or simply
a safe mating
