Effects of Turbidity on Anti-Predator Response and Foraging Behavior in the Fountain Darter, Etheostoma fonticola




Becker, Lily J. Swanbrow

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Turbidity resulting from anthropogenic stressors poses a significant threat to freshwater systems and is occurring on a global scale. The pervasive impacts of turbidity include degraded visual ability resulting in altered animal behavior. Anti-predator response and successful foraging ability, both essential elements of ecological communities, are two aspects of behavior that can be affected by turbidity. The federally endangered fountain darter (Etheostoma fonticola) is an important species for investigating the impacts of turbidity on behavior. Etheostoma fonticola is endemic to the clear, spring-fed waters of the San Marcos and Comal Rivers. These rivers are currently subject to a number of anthropogenic threats that may affect turbidity such as pollution, climate change, and increased recreational use. I tested the affects of clear water and low (~30 NTU) turbidity on anti-predator response and foraging behavior in E. fonticola and found that E. fonticola requires a combination of visual and chemical cues to respond to a native fish predator. However, low turbidity did not significantly affect anti-predator response. Given that turbidity degrades vision, these results imply that higher turbidity levels than included in my study may impact anti-predator response. I also found that prey consumption and time spent searching for prey were significantly altered across three levels of low to medium turbidity compared to clear water. Prey-capture success was not affected by increased turbidity. Thus, foraging behavior is significantly compromised even at relatively low levels of turbidity. These results suggest that the affects of turbidity on foraging and anti-predator behavior may be of considerable concern in E. fonticola habitat.



Turbidity, Behavior, Etheostoma fonticola, Anti-predator, Foraging


Becker, L. J. S. (2012). Effects of turbidity on anti-predator response and foraging behavior in the fountain darter, etheostoma fonticola (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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