How does the Territorial Butterfly Chrysozephyrus smaragdinus Resolve its Contests? pp. 271-286
Authors: (Tsuyoshi Takeuchi, Center of Ecological Research, Kyoto University, Hirano, Otsu, Japan)
Abstract: Males of many butterfly species hold mating territories over which they compete with conspecific males. A typical contest consists of two males flying around each other without contact until one of them retreats. This behavior is generally regarded as a war of attrition, where both contestants continue to display and the one that retreats earlier is the loser. Butterfly contest resolution is difficult to understand because there seems little risk of injury during fights and the costs imposed on an opponent are not obvious. Using a territorial butterfly, Chrysozephyrus smaragdinus, a series of studies was performed to clarify how this butterfly resolves its contests. Field observations revealed that territorial owners almost always won contests against intruders. The most natural explanation for the owners‟ dominance is that individuals with higher resource-holding power (RHP) become and remain owners. However, territory owners did not exhibit superiority in body size, flight-muscle ratio, energy reserve, or age, which indicates that owners‟ dominance could not be attributed to these physical and physiological factors. Another likely explanation for the owners‟ dominance is that owners evaluate their territories more highly than intruders do, and therefore, are more motivated to fight for them. Removal-replacement experiments showed that males fought longer in defense of a territory as their duration of residence in the territory increased. This result indicates that individuals become more motivated to fight for a territory site as they become familiar with it. Since an owner is the individual that has occupied the territory the longest, he should be most strongly motivated to defend it, which may in turn cause his great superiority.