Male-biased sexual size dimorphism is typical of polygynous mammals, where the degree of dimorphism in body mass is related to male intrasexual competition and the degree of polygyny. However, the importance of body mass in monogamous mammals is largely unknown. We investigated the effect of body mass on life-history parameters and territory size in the red fox (Vulpes vulpes), a socially monogamous canid with slight sexual dimorphism. Increased body size in males appeared to confer an advantage in territory acquisition and defense contests because heavier males held larger territories and exerted a greater boundary pressure on small neighbors. Heavier male foxes invested more effort in searching for extra-pair matings by moving over a wider area and further from their territories, leading to greater reproductive success. Males that sired cubs outside their own social group appeared to be heavier than males that only sired cubs within their social group or which were cuckolded but our results should be treated with caution as sample sizes are small. Territory size, boundary pressure and paternity success were not related to male age. In comparison, female body mass was not related to territory size, probability of breeding, litter size or cub mass. Only female age affected probability of breeding: younger females reproduced significantly less than older females, although we did not measure individual nutritional status. Thus body mass had a significant effect on life-history traits and territory size in a socially monogamous species comparable to that reported in polygynous males, even in the absence of large size dimorphism.
|Translated title of the contribution||Body mass, territory size and life-history tactics in a socially monogamous canid, the red fox|
|Pages (from-to)||1481 - 1490|
|Number of pages||10|
|Journal||Journal of Mammalogy|
|Publication status||Published - Dec 2008|