A deer's antlers are made of bone and living tissue. Every spring they slowly begin emerging from the male's head. They keep growing throughout the summer and into autumn; around September, they stop. He uses them throughout autumn to spar with other deer. During winter, they drop off of his head as part of his annual shedding process. He will start over with new ones the following spring.
Shedding the Antlers
Between the cold, the lack of food and the threat of hunters and other predators, winter is a particularly stressful time for a deer. His testosterone levels naturally drop, too, causing the cells that connect the antlers to his skull to absorb the antlers' calcium. This and the deer's stress level weaken the antlers so much that they eventually drop off sometime between December and March -- not always at the same time -- and are left behind. The skull bleeds and scabs over, healing so the antlers can grow back in the spring. In the meantime, the antlers that he shed are eaten by smaller animals like squirrels, who benefit from whatever calcium remains.
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