The role of evolution in mating behavior of lekking species  (Page 7/11)

This study also demonstrates the importance of fluctuations in food supply on the breeding season of manakins (Théry 1991). Females tended to favor certain nutrient resources over others, and males congregated around these regions of fruit density during breeding seasons. Thus, breeding success is positively correlated with fruit supply and resource distribution shows itself to be a driving force in communal displays (Théry 1991).

Neotropical birds

Researchers at the University of British Columbia in Canada conducted another study supporting the role of hotspots in lekking behavior. They followed four neotropical bird species, the ochre-bellied flycatcher ( Mionectes oleaginous ), red-capped manakin ( Pipra mentalis ), blue-crowned manakin ( Pipra coronata ), and long-tailed hermit hummingbird ( Phaethornis superciliosus ) (Westcott 1994). The researchers monitored annually male displaying behavior and location of lek center in canopy trees in Corcovado National Park in Costa Rica. The lek distributions were also analyzed for any correlation with geographic qualities of the area that would have an influence on them, such as waterways and drainage.

The results determined an underlying factor that affects the lek location distributions of all four species, and the researchers propose the geographic features as probable causes. The four species all demonstrate similar movement through the canopies and therefore are expected to show the same effects of the influence of the geography. The features of the land focus the movements of the females, causing males to cluster in these areas (Westcott 1994).

The potential influence of predators on lek distributions was overruled because, in 500 hours of study, only two instances of predation were noted. If the males were congregating to take advantage of the ability of clusters to fare better against predators, the other leks should be expected to notice the attacks. Contrarily, however, the calling of the other leks had no correlation with predation. It did not stop in response to the predation of neighbors and it did not increase to signal the arrival of a predator (Westcott 1994).

The study concluded in support of the hotspot hypothesis under certain conditions. Because an area of higher female density, where males are likely to visit, is likely to be very large to accommodate all of the females, many proclaim that it is unlikely to produce the clustering of males that characterizes a lek. However, the researchers at the University of British Columbia claim that if other factors are severe enough to constrain the movement of females, hotspot explanations alone may be sufficient to explain the leks (Westcott 1994).

Opposition

A study conducted by Jakob Bro-Jørgensen and other researchers from the Institute of Zoology in London refuted the hotspot hypothesis in a study on topi antelopes. Antelopes lek similarly to manakins, with this study focusing on leks of between 11 and 14 males each, visited by groups of up to 40 females (Bro-Jørgensen 2002). The hotspot hypothesis predicts that resource density would be greatest on lek as benefit to the females, which, in turn, attracts the lekking males. Instead, the results of the study determined the land on leks to be nutritionally deficient. The ground was bare and females grazed off lek close to 7 times more often than they grazed on lek (Bro-Jørgensen 2002). This indicates that the females gained no benefit in resources from the location of the lek, which refutes the hotspot hypothesis.