a study conducted by Pepper W. Trail, the interactions between adult males, females, and yearlings were observed and linked to mate choice and male dispersion patterns within leks. Adult males produced this disruptive behaviour with varying intensity, which depended on the situation. In lower-intensity disruptions, males usually directed their aggression or threats towards neighboring males, in attempts to improve or maintain breeding status and success. The males that were hassled tended to be more successful and often were disrupted with much greater frequency than males with lower mating success. Higher-intensity disruptions were used by less successful males and directed towards females that wandered by. This behaviour is suggested to have the effect of redirecting females towards the hassling male. Yearlings often disrupted courtships of the more mature adults on the basis of practice for future courtships, since the yearlings do not possess any territory within the lek. Female disruption was an uncommon event that had little, if any, effect on the accessibility of a male. Young males of highly promiscuous species such as the Cock-of-the rock often failed to mate in their first year, probably because older, more experienced males will enjoy the majority of matings. In this strong system of sexual selection, the successive breeding of dominant and aggressive males leads to high sex drives and the endurance of polygyny. A theory suggests that the selection of these aggressive males also puts a premium, or value, on female characteristics. Hence, there is a less likely occurrence of female–elicited aggression. Male Guianan cock-of-the-rock "delight in homosexuality" with almost 40 percent engaging in a form of homosexual activity and a small percentage never copulating with females. Ecological consequences of breeding One possible advantage to lek formation (in Guianan cock-of-the-rock and other species) is severe selection and consequent rapid evolutionary advancement, all of which is possible due to the high expendability of males. Only a few males are needed to fertilize the next generation. The courtship behaviour is similarly theorized to have arisen from differences in division of labour between the two sexes. Females expend their energy on building nests and rearing young, while males spend most of their time and energy of finding mates and caring for their plumage. Guianan cocks-of-the-rock form large leks, averaging 55 adult males. The males in these display leks were especially vulnerable to attacks and predation by large snakes and other natural predators. In manipulated groups