DECIDUOUS NATURE OF DEER ANTLERS 353 



variations in the daily amount of light play a greater role than does 

 the absolute duration of daylight in regulating antler and reproduc- 

 tive periodicities. 



Influences of Internal Factors 



The control of antler shedding is also affected by certain second- 

 ary factors, not the least of which is age. Young bucks bearing their 

 first set of antlers, which are usually unbranched spikes, invariably 

 shed later than do older members of their species. The difference 

 may be rather small, as in sika and fallow deer, in which the year- 

 lings shed their antlers in late May or early June whereas mature 

 animals do so usually in late April or early May. In other species, 

 there is a somewhat greater age difference. Young roe deer usually 

 lose their antlers in January or February, whereas mature ones shed 

 in late November or December. Very old bucks are reported to have 

 shed in late October or early November. In the moose, year-old 

 males drop their antlers in May or June, young adults shed in 

 February or March, fully grown bulls usually lose their antlers in 

 late December or January, and old ones may shed them as early 

 as November. A similar pattern is exhibited among reindeer and 

 caribou, the young males losing their antlers about April and the 

 oldest ones shedding them in late October or early November, with 

 intermediate ages in between. Initiation of new antler growth is 

 deferred until spring in most species of deer regardless of whether 

 the previous antlers were shed in the autumn, winter, or spring. 

 Nevertheless, older animals begin to grow new antlers earlier than 

 younger ones. Thus, the larger the antlers, the longer is the growing 

 season in which they can develop. 



In reindeer and caribou, antler shedding is influenced by sex, for 

 females as well as males carry antlers. As mentioned above, adult 

 males shed their antlers in fall or winter. Calves of both sexes, how- 

 ever, do not shed them until spring. In the adult female the antlers 

 are likewise retained until spring, eventually to be shed either just 

 before, or more commonly soon after, parturition. The temporal 

 correlation between these two events is so marked as to suggest a 

 causal relationship. Indeed, it has been noted by Kelsall (1962), 

 Lent (1962), and McEwan (1962) that barren female caribou 



