The metabolic costs of contest behavior in the stalk-eyed fly, Teleopsis dalmanni

Stalk-eyed fly (Teleopsis dalmanni) males are subject to sexual selection for large eye-stalks, and males with larger eye-stalks have increased mating success in part because they are more likely to win male-male contests. Agonistic behaviors are generally energetically costly. Depending on the nature of the fight there may also be other costs such as injury, death, or decreased reproductive success. The energetic costs of aggressive behavior in sexually dimorphic species can impact the outcome and duration of fights over food resources and mates. Fights in T.dalmanni have been shown to escalate from low-intensity to high-intensity aggressive behaviors with a pattern that fits the sequential assessment model. Both high-intensity and low-intensity fighting tactics require energy expenditure through respiration, and the metabolic costs of a contest may depend on the intensity of the tactics. By examining the change in concentration of CO2 during a contest it is possible to measure the metabolic costs of the contestants. In this project I found the energetic cost of fighting in T. dalmanni using a CO2 probe and although respiration is not linked to duration of male-male interactions, there are specific agonistic behaviors that predict both change in CO2 and fight duration