Chemical cues associated with visually elaborate aggressive displays of three-spine sticklebacks.

A two-choice chamber was used to determine if three-spine sticklebacks could distinguish between water conditioned by a displaying male and water conditioned by a male that was active but not displaying. Both nonterritorial males and gravid females appeared to recognize which male was displaying; i.e., males and females were more likely to bite or bump the substrate in front of a chamber receiving water from a displaying male. Nonterritorial males were more likely to enter the chamber receiving water from a male that was not displaying; gravid females entered the chamber that received water from the displaying male more often than males but not more often than expected by chance. The aggressive displays of male sticklebacks may have both visual and chemical components; alternatively, the fish may have been capable of detecting chemical by-products associated with different rates of physical activity.