360 R. J. GOSS 



mature loss of antlers in male deer, and parturition is accompanied 

 by shedding in female reindeer and caribou. Common to these two 

 phenomena is an abrupt decrease in the secretion of sex hormones, 

 an effect which might be causally related to antler shedding. 



It remains to be determined how the effects of decreased testoster- 

 one are related to antler shedding and replacement. Conceivably, 

 simple release from the inhibiting effects of testosterone might bring 

 about shedding. Yet experiments by the author in which 4 normal 

 male sika deer were injected with heroic doses of testosterone pro- 

 pionate (Oreton; Schering Corporation), amounting to 5.5 gm per 

 deer in 6 doses over a 3- week period from September 21 to October 

 11, failed to induce the shedding of antlers upon abrupt cessation of 

 injections. Thus, a relative decrease in testosterone levels from super- 

 normal to normal is not sufficient to mimic the effects of castration 

 on antler shedding. 



It is possible that a stimulating effect might be involved in antler 

 shedding. If so, such an influence could be mediated either by nerves 

 or by hormones. With reference to the former, the experiments of 

 Wislocki and Singer (1946) show that denervated antlers grow 

 abnormally ( probablv owing to injuries resulting from loss of sensory 

 innervation) but that the velvet is lost and the antlers are shed at 

 normal times. Waldo and Wislocki ( 1951 ) , however, mention cer- 

 tain abnormalities in the shedding mechanism of the denervated 

 antler. 



The first step in analyzing the operation of endocrine factors in 

 regulating antler loss and regeneration is to determine what glands 

 might be involved. With the exception of gonadectomies, no en- 

 docrine deletion experiments have been performed on adult deer 

 and only a few have been attempted on immature ones. Therefore, 

 one cannot rule out the possibility that almost any gland might 

 secrete an antler-influencing hormone. 



Literature on the relation of the thyroid gland to antler growth 

 cycles is somewhat contradictory. Grafflin ( 1942 ) noted no signifi- 

 cant seasonal changes in thyroid histology in the Virginia deer. 

 Freundova ( 1955 ) , however, described decreased thyroid activit) 

 characterized by low epithelium and large follicles during periods 

 of sexual repose in the red deer. In correlation with the onset of 



