To defend or not to defend? Size, residence, and conditional mating in male variegated pupfish, Cyprinodon variegatus

Abstract

In both the field and laboratory, we investigated the competitive strategies of different-sized residents and intruders in a species with multiple male mating tactics (i.e. territorial defense and sneak spawning), the variegated pupfish, Cyprinodon variegatus. Medium and large males were observed defending territories in the wild, and these two sizes of residents dominated all intruders in the laboratory in both the presence and absence of a female. Under laboratory conditions, some small males defended territories, but a relatively high proportion of small residents were defeated by intruders. When a female was present, intruders of all sizes frequently interrupted the spawning attempts of residents. Although no size of intruder in the laboratory interrupted more than the others, the tactics used by the different intruders to interrupt were different. Medium and large intruders were disruptive to the spawning pair, eliciting aggression from the resident, while small intruders sidled with a spawning pair, often without response from the resident, allowing the female to deposit an egg before leaving. These results suggest that medium and large males use overt aggressive behaviors to interrupt spawns; in contrast, small males devalue territory possession and rely on more surreptitious tactics to spawn.