STUDIES ON GROWTH OF DEER ANTLERS 



II. Seasonal changes in the male reproductive tract of the Virginia deer 



{Odocoileus virginiafius borealis), with a discussion of the factors 



controlling the antler-gonad periodicity* 



A NUMBER of authors mention briefly the observation that the testes of deer 

 , undergo seasonal enlargement and spermatogenesis, but little in the 

 way of actual evidence has been submitted to give a concise picture of the 

 seasonal changes. For the European roe deer (Capreoliis capreohis) the frag- 

 mentary observations of Ziegler," Bischoff/^ Keibel,' ' Retzius,"^ Strahl/ Len- 

 ninger/' and Stieve" can be combined to establish the fact that the testes begin 

 to swell in the spring, attaining their maximum size in June, July, and August, 

 when breeding occtirs. In the fall the testes undergo involution and by winter 

 are reduced to one-third their former size. Spermatogenesis apparently com- 

 mences in the spring (Stieve) and ceases, according to the somewhat conflict- 

 ing statements of different observers, sometime in October or November. In 

 midwinter (December and January) there are no traces of spermatozoa. For 

 other species of deer little is known beyond the fact that the testes undergo 

 periodic swelling, being largest at the time of the rutting season. 



The present account deals with the seasonal changes in the testes and sem- 

 inal vesicles of the Virginia or white-tailed deer {Odocoileus virginiamis 

 borealis). The material consists of the reproductive tracts of adidt Virginia 

 deer secured throughout the year at intervals of one or two months. The ma- 

 terial was obtained by permission of the trustees of Naushon Island, Massa- 

 chusetts, with the help and interest of Dr. Henry S. Forbes to whom especial 

 thanks are due. The deer were taken from a herd of several hundred animals 

 on free range on Naushon Island. 



The weight of the testes, with epididymides attached, was recorded in each 

 instance. The testes and male accessory glands were fixed in Bouin's fluid or 

 lo per cent formalin. The histological sections were stained with haematoxylin 

 and eosin. No provision was made to weigh the entire animals, so that testes- 

 body-weight ratios are lacking. 



Seasonal Changes in the Male Reproductive Tract 



Testes. The weights of the testes in thirteen adult deer are presented in table 

 1. It will be observed that the weight of the testes fluctuates seasonally, with 

 the maximum weight in the fall at the period of riuting, and the minimum 

 weight from late winter until early summer (graph i). 



Examination of the histological sections (pi. i, figs, i to 4) reveals the pres- 



* A summary of the present investigation ^\'as gi\en at the meeting of the American Asso- 

 ciation of Anatomists in Chicago in 1941.^ 



[63'] 



