Androgens and Antlers

As a biologist I’m fascinated by natural processes, such as evolution. Sexual selection is regarded as a driving force for the evolution of male secondary sexual characteristics. These characteristics include for example courtship behaviours and the expression colourful displays in birds. Research has shown that in many cases the expression of these behaviours and morphological traits are controlled by androgenic hormones such as testosterone. A very clear example of such androgen driven male sexual signals in mammals are the antlers that males of many cervid species carry. However, antlers are not confined to deer, moose, reindeer and others. This weekend we found a wonderful creature that also carries structures that we happily call antlers: the stag beetle. Not only the antler-like structures, but also its name, including the Latin name “Lucanus cervus“, reminds of deer. The structures we call antlers are of course not true antlers. They are not bony structures on the skull but they are strongly specialized and enlarged mouth parts or mandibles. The growth of the mandibles may be stimulated by the hormone ecdyson and similarly as in cervids, the “antlers” of the stag beetle are subject to sexual selection. Males fight each other with their mandibles over access to females. I’m not aware whether evolution through female mate choice shaped the morphology of these beetles as well. The end result stays of course the same: a very spectacular beetle that gained my respect (those mandibles do look a bit scary – wouldn’t like to get my finger squeezed in there!)

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