8o4 R. J. GOSS 



usuallv shed their antlers before fertile ones do, i.e., in the winter 

 or early spring. Therefore, the condition of pregnancy appears to 

 delay the loss of antlers, perhaps because of the heightened produc- 

 tion of sex hormones. As will be described below, shedding of ant- 

 lers in other species of deer can be postponed bv injections of either 

 testosterone or estrogen. 



There is good reason to believe that the sequence cf events lead- 

 ing from day-length changes to antler shedding is mediated by 

 hormones. This is suggested bv such correlations as the relation 

 between shedding and rut. In older and presumably more virile 

 males, antlers are shed sooner after the breeding season than in 

 vounger animals. In the female reindeer and caribou, one would 

 suspect that antler shedding is stimulated by endocrine factors as- 

 sociated with parturition or lactation. Wislocki et al. (1947) sug- 

 gested that the male counterpart of the lactogenic hormone might 

 logically be involved in antler growth regulation. 



The hormonal basis of antler shedding has been most clearly 

 established, however, by investigations of the effects of castration. 

 The profound consequences of castration have been studied bv nu- 

 merous investigators, notablv Gaskoin (1856), Caton (1877), Fowler 

 (1894), Rorig (1907), Tand'ler and Grosz (1913), and Zawadowsky 

 ( 1926), as well as more recent investigators to be mentioned below. 

 This operation, when performed on fawns prior to the initiation of 

 antler development, precludes antler formation altogether. Its effect 

 on mature antler-bearing animals, however, depends upon the con- 

 dition of the antlers at the time of the operation. Castration of 

 bucks with growing antlers inhibits shedding of the velvet and 

 results in the permanent retention of viable antlers. But when a 

 deer is castrated after the velvet has been rubbed off and the antlers 

 are burnished and dead, shedding occurs approximatelv a month 

 later and new antlers are grown which remain in velvet permanently 

 thereafter. Such castrate antlers continue to grow each succeeding 

 spring and summer, adding to what has previously been formed or 

 replacing what mav have been lost by necrosis after winter freezing. 

 In this way, rather bizarre headpieces may develop. In some species, 

 such as the sika and fallow deer, the antlers may become crooked 

 outgrowths lacking the normal number of branches. A Virginia deer 



