Boldness and exploratory behaviors differ between sunfish (Lepomis spp.) congeners in a standardized assay

The shy-bold behavioral continuum is an element of animal behavior which is often studied for its ecological relevance, particularly in the context of predation risk. How individuals respond to various predation cues is well studied at the individual level, but relatively little is known about how these responses can differ among closely related species. We exposed individual wild-caught juvenile bluegill ( Lepomis macrochirus ) and pumpkinseed ( L. gibbosus ) to kairomones of a common predator (Northern pike, Esox lucius ), conspecific alarm cues, or a lake water control in a Z-maze trial commonly used to assess relative levels of bold and exploratory behaviors. Neither species exhibited any significant behavioral responses to either predation cue, but bluegill consistently displayed more bold-type behaviors than pumpkinseed. Although the lack of a behavioral response to predation cues in this study is equivocal, we identify clear differences in boldness between these two congeners and discuss the possibility of ecological niche differentiation driving these behavioral differences. Significance Statement Closely related species exposed to similar predator guilds may differ in their behavioral responses to predation risk, particularly during different life-history stages. We exposed juveniles of two co-occurring sunfish congeners ( Lepomis spp.) to chemical predation cues (predator kairomones or conspecific alarm cues) in a Z-maze assay to assess relative levels of bold and exploratory behaviors. Bluegill ( L. macrochirus ) were consistently bolder and more proactive than pumpkinseed ( L. gibbosus ). Ontogenetic ecological niche differentiation between these species may be the cause of these observed differences and life-history trajectories should be considered in the design of future research questions.