Foraging Behavior of Antlion Larvae
Date Issued
2011
Date
2011
Author(s)
Tsao, Yu-Jen
Abstract
Antlions are trap-building insects, but their foraging behavior does not simply consist of the pit construction. To date, a number of aspects of the pit-trapping behavior in antlions have been examined; however, the decision-making mechanisms underlying the observed behavioral responses remain largely unknown. In this thesis, I examined two aspects of the pit-foraging behavior of antlions. A common antlion species in Taiwan, Myrmeleon persimilis, was used as the model organism. In Chapter 1, brief descriptions of the natural history of antlions and the focal species are presented.
The first aspect of the pit-foraging behavior examined in this thesis is the act of pit foraging itself. That is, although antlions are typically considered to forge with pits, they can also ambush prey without using pits. Why antlions switch between the two strategies is not fully understood. In Chapter 2, using a dynamic optimization model, I show that the strategy-switching behavior is the optimal foraging strategy under a variety of ecological conditions. In particular, the model predicts that antlions should exhibit the pit-trapping strategy when their energy status is low and should use the ambush strategy when their energy status is high. One of the key assumptions leading to this result is an ecological tradeoff associated with the pit-foraging strategy where pit-foraging increases prey capture success but also increases predation risk. The prediction and the assumption of the model were empirically verified. These results suggest that antlions dynamically choose their strategies to maximize fitness by balancing the cost and benefit of the pit-trapping vs. ambush strategies.
The second aspect concerns a spatial aspect of pit-foraging. Antlion pits are commonly found in aggregations in the field, but finding disadvantages of the aggregation (e.g., predation risk and competition) is easier than finding an advantage of it. Thus the pit aggregation is an ecological conundrum. In Chapter 3, I offer an explanation for the aggregation behavior from a game theoretical point of view. By using a spatially explicit individual based model, an ecological scenario where two antlions forage in the common environment was simulated, and how different relocation strategies affect their fitness was examined. The results confirmed that a strategy leading to aggregations (i.e., relocate less when other individuals are nearby) can be the unique evolutionarily stable strategy. To validate the theoretical result, whether antlions follow the evolutionarily stable strategy was empirically examined. The presence of neighbors was simulated by sand tossing, and antlions that received the simulated sand tossing decreased their tendency to relocate. These results suggest that antlions aggregate because the presence of neighbors contains important information about the site quality, and the behavior has been selected through the evolutionary game.
Subjects
antlions
Myrmeleon
foraging behavior
ecological tradeoff
aggregation
evolutionary game theory
relocation
Type
thesis
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