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 of smaller size, around 6, predation was less likely to occur, due to an inverse relationship between the number and frequency of attacks and the size of leks. Thus, with a smaller frequency of attacks on the smaller group, the Guianan cock-of-the-rock males was less likely to flush or disperse completely as compared to a large group where a false alarm could trigger a complete flush 90% of the time. It was found that these birds have relatively ineffective methods of anti-predation and that social anti-predation and the infrequency of encounters with predators were keeping these lekking males alive.