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13 



The Deciduous Nature of Deer Antlers 



RICHARD J. GOSS, Department of Biology, Brown University, Provi- 

 dence, Rhode Island 



FEW events in nature rival the unique mechanisms by which the 

 annual renewal of antlers is achieved. The rate at which antlers must 

 elongate in order to attain lengths of up to 4 feet or more in growing 

 seasons of only a few months may exceed 1 centimeter per day, a 

 growth rate probably unequaled elsewhere in the animal kingdom. 

 Once the ultimate dimensions are reached, the entire antler dies, 

 whereupon the \'elvet\^ skin peels off revealing the compact bone 

 beneath. As nonliving structures penetrating the epidermis (Fig. 9), 

 antlers represent one of the rare instances, together with teeth and 

 the placoid scales of elasmobranchs, in which the continuity of the 

 skin is naturallv, though temporarilv, interrupted. Serving as weap- 

 ons and status symbols during the rutting season and for varying 

 periods thereafter, the burnished antlers are shed as the succeeding 

 year's set begin to grow. This is achieved by osteoclastic activity at 

 the junction between the dead bone of the basal part of the antler 

 and the living bone of the frontal pedicle from which the antler 

 originates. 



The shedding of antlers represents an extreme instance of a 

 rather common biological phenomenon, usually represented by the 

 loss of certain epidermal structines in various animals following 

 their respective breeding seasons. The pronghorn antelope, for 

 example, sheds the outer keratinized sheaths of its horns annually 



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