Body size and fat reserves as possible predictors of male territorial status and contest outcome in the butterfly Eumaeus toxea Godart (Lepidoptera : Lycaenidae)

We used adults of the butterfly Eumaeus toxea for two purposes—description of male territorial behavior and investigation of whether body size and muscle fat reserves correlated with social status (resident or intruder) and the probability of winning a territorial contest in dyadic encounters. Males perched in places near cycads (Zamia furfuracea), where females lay eggs. Resident males (those with faithfulness to the same site for several days) used two types of flight of different duration, short (ca. 5 s) and long (ca. 17 s), against male conspecifics. Because of this difference the latter were regarded as true contests. Males that copulated were residents and were also larger than males not observed in copulation. Residents and winners of contests were larger and fatter than intruders (males entering the site that faced a resident with a long-lasting flight) and losers of contests, respectively, possibly because these last two categories of male were individuals with already exhausted energy stores. Body size and fat reserves seemed to correlate with status for resident and intruder males but not for winner and loser males. This possibly means that body size reflects male energy condition. This is supported by the fact that large, resident males are confronted in short contests, in contrast with small, resident males. Our study suggests that the role of size and fat reserves during contests cannot be discounted in butterflies.