A year-round supply of lovely, available mates gives male butterflies on the island of Madeira something extra to live for—something that Swedish males don’t have.
Male Pararge aegeria butterflies live longer on Madeira, off the North African coast, than in Sweden, report Karl Gotthard of the University of Neuchatel in Switzerland and his colleagues. This difference fits predictions that organisms invest resources only where they pay off in reproductive success, the researchers comment in the January Oecologia.
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