Sexual size dimorphism in musteloids: An anomalous allometric pattern is explained by feeding ecology

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Abstract
Rensch's rule states that sexual size dimorphism (SSD) increases with body size in taxa where males are larger, and decreases when females are larger. The dominant explanation for the trend is currently that competitive advantage for males is greater in larger individuals, whereas female size is constrained by the energetics of rearing offspring. This rule holds for a variety of vertebrate taxa, and opposing trends are rare. We examine the allometry ofSSDwithin the Musteloidea and demonstrate a hypo‐allometry contrary to Rensch's rule, with lowerSSDassociated with larger body size. We provide evidence that feeding ecology is involved. Where diet promotes group‐living, the optimal strategy for the males of larger species is often not to attempt to defend access to multiple females, obviating any competitive advantage of relatively greater size. We conclude that the effect of feeding ecology on mating systems may be a hitherto neglected factor explaining variation inSSD.
Funding Information
  • Natural Sciences and Engineering Research Council of Canada

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