352 R- J- Goss 



species to tropical zones. It would be interesting to learn if such 

 deer and their offspring would continue on an annual schedule 

 coincident with that of their original habitats in the near absence 

 of seasonal variations in the environment. 



Attempts have been made, however, to transfer various species 

 of deer from northern temperate zones to New Ziealand (Donne, 

 1924; Marshall, 1936, 1937). Following such transequatorial shifts 

 of red deer, fallow deer, moose, wapiti, and Virginia deer, the antler 

 and reproductive cycles readjusted to the seasonal reversal. Clearly, 

 these animals shed their antlers in response to the seasonal changes 

 to which thev are directly exposed. Indeed, it is possible to change 

 the antler growth cycles according to artificially altered day lengths, 

 as has been proved by Jaczewski ( 1954 ) . In these classic experi- 

 ments, red deer which had already begun to grow their antlers were 

 confined in a darkened building from 4 p.m. until 8 a.m. daily. Sub- 

 jected to suddenly decreased day length from late March or early 

 April until June or July, these animals completed the development 

 of their antlers, shed their velvet, and manifested precocious rutting 

 behavior. Several weeks after they were returned to the normal 

 summertime day lengths, the antlers were shed and new outgrowths 

 were produced during what remained of the summer. The velvet 

 was next shed in September, but antlers were retained until the 

 usual shedding dates the following spring. Thus, it has been possible 

 to induce the formation of two sets of antlers in a single year by the 

 appropriate manipulation of day lengths. Decreases in day length 

 accelerate maturation of the antlers and hasten the onset of rut, 

 whereas increased day lengths stimulate shedding of the antlers in 

 the red deer. Experiments by French et al. (1960), however, in 

 which Virginia deer were exposed to artificial 16-hour days and 8- 

 hour nights starting in October, failed to have marked effects on 

 antler growth cycles. Under these conditions, antlers were shed only 

 2 to 3 weeks earlier than controls despite sustained exposure to 

 prolonged day lengths for li years. The fact that Virginia deer 

 shed their antlers in the winter when the days are short (whereas 

 red deer shed in the spring) may account for the relatively poor 

 response in the former species to increased lengths of daylight. 

 Nevertheless, investigations such as these tend to indicate that 



