Biology Reference
In-Depth Information
(a)
(b)
40
80
Uganda Kob
White-bearded Manakin
30
70
n
= 438
n
= 64
20
60
10
50
1
2
3
4
5
6
7
8
9
10
12
14
16
18
20
22
40
Males on Lek in rank order of success
(c)
30
50
Sage grouse
20
40
10
30
n
= 105
1
2
3
4
5
6
7
8
9
10
20
Males on Lek in rank order of success
10
1
2
3
4
5
6
7
8
9
10
12
14
Males on Lek in rank order of success
Fig. 9.4
On leks, most of the copulations are performed by just a few of the males. (a) Uganda kob
Adenota kob thomasi
. From Floody and Arnold (1975). (b) White-bearded manakin
Manacus manacus trinitatis.
From Lill (1974). (c) Sage grouse
Centrocercus urophasianus
. From Wiley (1973).
Why do the males aggregate into leks? Five main hypotheses have been proposed
(Bradbury & Gibson, 1983).
Males aggregate on 'hotspots'
Male aggregations may be explained by the familiar scheme in Fig. 9.1, with males
settling in areas where female encounter rate is particularly high (hotspots). In sage
grouse, leks are located in areas where females travel between their wintering and
nesting ranges. Furthermore, the numbers of males on a lek is related to the number of
females nesting within a 2 km radius, suggestive of 'hotspot' settlement by males
(Gibson, 1996). In the lekking sandfly
Lutzomyia longipalpis
, too, males aggregate on
hotspots, namely vertebrate hosts, which females visit to obtain a blood meal. Several
hundred males may occur in a lek, each defending a tiny territory (about 2 cm radius)
where they jostle and fight for space. Experiments in which the numbers and distribution
of chicken hosts were varied, using cages, showed that males quickly aggregated on
new hotspots when host distribution was changed, with larger leks where there were
most hosts (Jones & Quinnell, 2002).
Leks may occur
where females
are abundant
