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Alternative tactics in reproductive behavior enable individuals to maximize their fitness in relation to competitors in the same population. In many taxa, territoriality is a common tactic of males to increase their reproductive success. In the bat Saccopteryx bilineata, territorial males defend roosting areas for females against other males and court females throughout the year. Peripheral males in the same colonies do not defend territories but compete with territorial males for reproduction with females. In this study, we monitored the behavior of the males in a natural colony over three reproductive seasons. We compared morphological and age data and measured the reproductive output of males adopting the territorial or peripheral tactic. No differences in body size or weight were detected between male types, but the probability of adopting a tactic seemed to be age dependent. Peripherals were often young males and replaced territorials in several cases, whereas the opposite case was not observed. Peripherals were not excluded from reproduction, but territorials were more likely to reproduce. Variation in reproductive success was high within both male tactics, and the reproductive success of some peripherals was comparable to territorials, but, on average, the reproductive success of territorials was more than twice as high. Therefore, behavioral tactics do not seem to be equally profitable in general but may represent different phases in the reproductive life of many S. bilineata males. Copyright 2002.