Abstract

Microhabitats with high structural complexity can impede visual information of local predation threats. This can shape individual behaviour, resulting in more fearful behavioural phenotypes within complex microhabitats. In this experiment, I explored the impact of environmental complexity on shaping individual predator avoidance behaviour. I observed the behaviour of bluegill sunfish (Lepomis macrochirus) along an environmental gradient. I predicted that as visual complexity of the environment increases, antipredator and neophobic response also increases. I conducted in situ observations at Lake Opinicon, where I presented bluegill sunfish shoals with a novel object and one of three different chemosensory stimuli (water, alarm cue or novel odour). Multiple regression analysis found that the strongest predictor, in shaping predator avoidance behaviour, is vegetation diversity. Bluegill sunfish exposed to conspecific alarm cues exhibited stronger avoidance responses under higher diversity patches. Additionally, bluegill sunfish were not neophobic to neither the novel object nor the novel stimuli. Other environmental factors, such as the ratio of open area to visually obscured area, height of vegetation, and depth of the water were not significant predictors of behavioural response. Bluegill sunfish, under elevated risk of predation, have previously been observed to seek refuge in areas of high vegetation, avoiding open, low complexity patches. Instead, I found that in this population of bluegill sunfish, response was not associated with the amount of vegetation within a patch, but more so with an increase in vegetation diversity. Areas with higher vegetation diversity can contain plant species of different spatial structures (broad leaved plants vs thin leaves), potentially obscuring more visual information to the individual. This high diversity may increase visual obscurity in this system, leading prey to respond to conspecific alarm cues with a strong antipredator response.