Stickleback distraction displays: sexual or foraging deception against egg cannibalism?

Abstract

Three-spined stickleback, Gasterosteus aculeatus, males guarding nests containing eggs were tested for their use of distraction displays against all-male, all-female and mixed male and female conspecific intruder groups. Distraction displays were used against all groups, suggesting that the display is a foraging rather than a sexual deception. Most males used two different displays, with the most obvious being employed primarily when intruders were close to the nest. Males also buried their nests with sand to protect them. Groups with male members made more territorial intrusions and fought more with the residents than all-female groups. However, nest survival-to-hatching was better in mixed and all-male trials than all-female trials. Raiding caused most nest destructions, although suffocation following burying killed some eggs. The high nest survival-to-hatching in the all-male and mixed trials probably occurred because some male intruders established territories. This reduced the number of fish in raiding groups and resulted in joint attacks by several territorial fish on the remaining group members. Resident males could control the remaining fish with aggression. Males guarding nests without eggs also used distraction displays, but they did not bury their nests.