The elaborate tail feathers of peacocks and impressive antlers of male deer have long fascinated those with an interest in animals. How could these traits evolve? Why are they dimorphic (usually only seen in the males of the species)? While the antlers could plausibly be an adaptation to thwart predators, surely this isn’t the case for the peacock’s tail feathers? The answer, it seems, lies in how individuals acquire mates. Females, by definition, produce few gametes (germ cells), but invest a relatively large amount of resources in each one. By contrast, males invest relatively little in individual gametes, but produce them in vast quantities. As a result, females (or more accurately their gametes) are limited, relative to males', and typically (although not always) males compete for reproductive access to females. It is now believed that the peacock's ornate tail serves to attract mates and the deer's antlers are used in physical combat among males for access to females. While these arguments (collectively termed 'sexual selection') have provided credible explanations for the evolution of these exaggerated traits, in some cases we are now faced with the complete opposite quandary. Specifically, why aren’t some animals, like the red squirrel, visually dimorphic? Put another way, if reproductive female red squirrels are a limited commodity, what traits are used by males to compete for access to them? Red squirrel males are only marginally larger than females, and don't possess either sexual weaponry like antlers, or ornamentation, suggesting that neither physical combat among males, nor visual attraction are important. At Kluane we are currently testing the hypothesis that the analogous trait to antlers and tail feathers in red squirrels is male behaviour. Because females defend individual territories, they are spatially scattered and males must search for reproductive opportunity. Could it be that the spatial abilities of male red squirrels represent their 'antlers'? To test this we following the males during the mating season to quantify their spatial behaviour and comparing their relative success, as the number of offspring that they sire. Should our hypothesis be supported, it could open the door to investigations of a far richer set of traits involved in sexual selection than has previously been appreciated.