Their ability and motivation to mate are primarily independent of day-length (photoperiod) and instead rely on cues from short-term changes in local conditions like rainfall, food abundance and temperature.
Another factor is the presence of suitable breeding sites, which may only form with heavy rain or other environmental changes.
Other categories of breeders that perhaps can be subdivided under the heading "opportunistic" have been used to describe many species, such as many that are anurans like frogs.
An example is the golden spiny mouse where changes in dietary salt in its desert habitat due to rainfall appear to cue reproductive function.
While reproduction is generally independent of photoperiod, animals can still experience reduced fertility with changes in day-length.