|MadSci Network: Zoology|
Why don’t female deer grow antlers? First, I must point out that some of them do. Female caribou and reindeer commonly grow antlers along with their male counterparts. In addition, some female white tail deer (and I suspect mule deer, although I don’t know for sure) will grow antlers. This phenomenon is well known to most deer hunters, who are not supposed to be shooting does but can get away with it if the doe has antlers. Now, to address this question (leaving out the exceptions noted above) we first need to ask – why should any deer grown antlers? Growing anything (an arm, a tail, or an antler) is associated with a metabolic cost – it takes food energy to grow that structure and gathering food exposes an animal to predation risk. Employing the adaptationist paradigm, we can assume that antlers serve a function that is important to males, but that function is not as important to females. In the case of deer, that function is the inter-male competition for mates. Deer really only use their antlers to fight with other deer. They are not usually used to fight off predators, which is one of the reasons that antlers are/can be shed annually. So, male deer need to antlers to fight with other male deer to gain access to females. Female deer do not employ the same competitive strategies among themselves, and so do not “need” antlers. What we see here is an example of sexual selection. Having large antlers actually works against the long term survival of the buck (these deer are the prime targets of hunters), but it does allow the buck to gain reproductive access to more females. And, from the biological perspective, reproduction is the entire purpose of existence.
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