Document: SAN-3-56-37

The effect of starvation, predator presence and time of day on aggregation and other risky behaviors in a Chironomid midge.

WARREN, C.T.* ¹, N.ADAMS ¹, E.NICHOLAS ², D.E.WOOSTER ¹ and S.J.DEBANO ¹

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

Abstract:
Aggregation behavior can be an appropriate antipredator response for animals that normally forage in open or exposed fashions. For animals that forage from sheltered locations, such as tube-building chironomids, aggregations most likely form for reasons other than predator defense, such as resource acquisition. In fact, aggregation behavior is risky in small aquatic invertebrates because aggregates are easily detected and eaten by fish or other large predators. We examined aggregation behavior in a chironomid midge, Chironomus riparius. Specifically, we examined whether larval midges form aggregates around dead midges, and whether factors that affect risk, such as hunger level, exposure to fish cues, and time of day affect aggregation behavior and other potentially risky behaviors. We found that larvae form aggregates around dead midges, but do not respond to factors that should affect risk-taking behavior. Hunger level, exposure to fish cues, and daylight did not affect aggregation behavior. However, hunger level and exposure to fish cues did affect other risky behaviors. Larvae exposed to fish cues built lighter tubes than larvae not exposed to fish cues, and starved larvae spent more time outside their tubes than well fed larvae. In addition, at night, starved larvae spent more time out of their tube than in daylight hours. Thus, we suspect that the cost-benefit ratio of aggregation behavior differs from other potentially risky behaviors examined.

Keywords: aggregation, antipredator behavior, hunger level

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