Much attention has been devoted to the study of factors that influence mating dynamics (Bateson 1983; Thornhill and Alcock 1983; Partridge and Halliday 1984; Smith 1984; Clutton-Brock 1988). Although many studies have suggested that competing demands, such as the need to gather food or avoid predators, should affect mating behavior (eg, search strategies, courtship, mate choice, and mating duration), few controlled experiments have been done to quantify these effects.

It is important to distinguish between the effect of mating activity on predation risk versus the converse effect of risk on mating. A number of studies have shown that mating activity alters predation risk. The act of searching for or attracting mates is often associated with increased susceptibility to predators (see, eg, Howard 1978; Ryan 1985; McCauley and Lawson 1986; Gwynne 1987). Copulation per se or the associated contact guarding can either increase risk (Ward 1986) or decrease risk (Sivinski 1980; Verrell 1985; McCauley and Lawson 1986). We predict that if mating activity increases risk, then when predators are present, organisms ought to decrease mating activity. More generally, we predict that organisms should decrease mating activity when faced with demands that conflict with mating; the degree of decrease should depend on the relative effects on fitness of mating, feeding, and antipredator behavior. To our knowledge, only four studies have addressed alterations in prey mating behavior in response to the experimental addition or removal of predators. Male tree frogs (Smilica sila) and male Tungara frogs (Physalaemus pustulosus) reduce their calling activity after exposure to model predators (Tuttle and Ryan 1982; Ryan 1985); the addition of predatory fish caused male guppies (Poecilia reticulata) to switch to a safer courtship strategy (Endler 1987); and the presence of predatory sunfish caused a semiaquatic bug (Microvelia austrina) to reduce its mating activity (Sih 1988). We know of no previous experimental work on the effects of predators on mate choice or mating duration (indeed, we know of only one nonexperimental study that discussed the effects of predation risk on mating duration: Strong 1973). Here, we describe the first study to address experimentally the effects of both predation risk and hunger on mating activity and mating duration. Our study examined the effects of predatory green sunfish (Lepomis cyanellus) on the behavior of fed and food-deprived water striders (Gerris remigis).