condition-dependent behaviour in the context of mating may result from changes in resource availability and intrasexual competition for mates. when competition decreases, the expression of alternative behaviours also decreases. changes in mating behaviours, especially among alternative males, have been documented in insects, fish, and amphibians upon removal of dominant males. additionally, the availability of mates and resources also affects the expression of alternative strategies within a sex. the gain or loss of territory has been shown to affect mating approaches among insect species, while the receptivity and spatial distribution of mates impacts tactics used among insects, fish, and mammals. mating behaviours are also affected by an individual's size and age, as smaller or younger individuals are more likely to attempt reproduction through alternative means, including mimicry or sneak tactics. as a result, the ability to choose a behaviour that maximizes fitness under certain circumstances evolves.