Individual motivation is more important than fighting ability to determine contest settlement in the dragonfly Micrathyria ungulata (#392)
Although fights over territories are common in many species, there is little consensus about the factors that determine when the loser give up the contest. Empirical evaluations often focus on the effect of individual fighting ability or the effect of individual motivation to settle a contest. However, the lack of consensus may occur if both factors interact to determine the contest winner. In this study, we use males of the dragonfly Micrathyria ungulata to evaluate if i) individual fighting ability, ii) individual motivation or iii) an interaction between both factors determine individual investment in territorial contests. To evaluate these hypotheses we conducted a fight induction experiment. In this experiment, we simulated the approximation of a potential intruder in the territory to trigger a territorial defense response by both resident (marked males present in the territory for some days before the beginning of the experiment) and substitute males (marked males that occupied the territories after the removal of the residents). Resident males fought for more time against the potential intruder than substitutes. However, traits related to fighting ability (i.e. body mass, residual muscle mass and residual fat content) did not affect the time invested in fight by residents or substitutes. The fact that resident males fought for more time indicates that they are more willing to invest in fights (and consequently have higher chances to win natural contests), regardless of their physical or physiological attributes. If this effect is common across species, distinct motivations among individuals should increase variation in mean fight times among rival pairs. Consequently, because studies intended to evaluate how rivals settle contests often relate fighting times with individual traits, they may have difficulties in detecting patterns if there is no control for differential motivation among individuals.