Sexually mature male specimens of Onychogomphus forcipatus perch on stones along the shoreline of rivulets waiting for mates. They react aggressively towards conspecific males. From time to time they fly around, mostly fighting other males. At uniform shorelines they often do not return to perch on the same site, but apparently choose perches at random. This is confirmed by a statistical analysis of the distribution of perching sites along the shoreline. It is concluded that males of O. forcipatus do not defend distinct territories but are aggressive without site attachment. This type of behaviour is considered as phylogenetically primitive in dragonflies.