Document: SAN-3-56-38

The influence of hunger level and fish cues on microhabitat Selection and tube-building by larval midges.

MARTINEZ, L.* ¹, D.N.TINNEY ¹, D.E.WOOSTER ² and S.J.DEBANO ¹

Trinity College, Washington D.C. 20017 USA ¹
University of Maryland, College Park, MD 20740 USA ²

Abstract:
A common trade-off that many animals face during their lives is that between foraging and predation risk. To balance this trade-off prey often choose among microhabitats that vary in predation risk as well as choose among other behaviors that influence risk (e.g., timing of feeding, movement rate). The larvae of a chironomid midge, Chironomus riparius, display a variety of behaviors, including microhabitat selection, and several antipredator behaviors, including the construction of tubes. We examined the effect of starvation level and the presence of fish cues on the selection of, and behavior in, two types of microhabitats: a food-rich habitat open to ambient light, and a food-absent, sheltered habitat. We found that both hunger level and the presence of fish cues affect the likelihood of making potentially risky microhabitat choices. Starvation increased the likelihood of engaging in risky behavior, while the presence of fish cues decreased the likelihood of engaging in risky behavior. Specifically, starved larvae spent significantly more time in the food-rich habitat (where they are more vulnerable to potential predators) than well-fed larvae. In addition, larvae exposed to fish cues spent significantly less time in the food-rich habitat than larvae not exposed to fish cues. Starvation level and presence of predators also influenced antipredator behavior in both microhabitats. In the presence of fish, larvae, in general, built more tubes, and in the absence of food, larvae built fewer, lighter tubes. Hunger level and fish cues also affected the proportion of tubes built on the food-rich, risky habitat. Starved larvae built a larger proportion of cases on the food-rich, risky side, while larvae in the presence of fish cues built a smaller proportion of cases on the food-rich, risky side. Thus, C. riparius adjusts its behavior, including microhabitat selection and tube building, to balance both feeding and antipredator demands.

Keywords: chironomids, microhabitat selection, antipredator behavior

This abstract is being presented at: 10:30 AM in session:
Poster Session #9: Fish, Lakes, Streams and Wetlands.