Deer antlers are a dual-use technology

IN MARCH 2015, braving the bitter cold of a Yellowstone winter to report on research being carried out there on wolves, your correspondent chanced upon a wolf pack as it attacked and killed a deer of the species known in North America as “elk”. (These are actually a type of red deer. True elk are called “moose” in North America.) Days later, all that remained was a bloody skeleton and a spectacular set of antlers.Dramatic as this scene was, it presented an evolutionary conundrum. Males grow antlers during the spring and summer, in order to fight one another for females during the rutting season, which is early autumn. Antlers are heavy. A full-grown male’s may weigh more than 17kg. It thus requires a lot of energy to carry them around. Yet March is many months after the rut. Moreover, the earlier a male sheds his antlers after rutting, the longer he has to grow a fresh pair for the following year’s shenanigans, and thus the bigger and more pointed those antlers can be. The conundrum, then, is why males do not dispose of these bony encumbrances immediately after the rutting season has ended.