It’s hard to imagine a day going by in any deer camp in North America without the conversation finding its way to antlers, specifically antler size. Hunters speak of “G-2s,” “inside spreads,” “drop tines” and “beam mass” with the fluency of wildlife biologists. But while most hunters are well versed in the lingo of antler appearance, the factors that influence the growth of these amazing appendages are less well understood.
In biological terms, the cycle of antler development is controlled by the buck’s endocrine system and involves a complex interaction between the brain, pituitary gland and testes in response to the length of daylight, also known as “photoperiod.”
The Growth Cyle
Antlers begin growing in the spring and summer, when testosterone levels in a deer’s bloodstream are at their lowest. The velvet-encased antlers are living tissue at this point, complete with circulating blood and sensory nerves, and are growing at an astounding rate: up to a half inch per day or more, which ranks them as some of the fastest-growing structures in the animal kingdom. Moose lay claim to the fastest-growing antlers, adding up to a pound of new antler per day!
With the shortening days of autumn, a buck’s testosterone levels begin to rise, the velvet dries and the antlers harden into dead bone. Then, in winter, when testosterone levels begin to diminish, the antlers fall off and the cycle begins anew.
As complex as this dynamic is, the trigger is the number of daylight hours. In experiments, captive bucks exposed to artificially short seasonal light cycles have grown and dropped as many as four complete sets of antlers in one year.
An Early Edge
Barring injury, the size of a buck’s antlers is determined by age (older bucks sport increasingly large racks until the age of 5½ to 7½); genetics (big-racked fathers and robust mothers); and nutritional intake.
Antler size in a deer’s first year and in subsequent years is largely a function of the diameter of the pedicle, the bony base from which antlers grow. A buck that grows small pedicles in its first year-due to a late birth or poor nutrition-might always have relatively small antlers, regardless of any inherited genetic disposition toward growing large antlers.
That’s the bad news. The good news is that physically superior bucks grow larger pedicles and small “button” antlers in their first year, and may even develop eight-point racks during their first full growing season. These rare bucks have the potential to become the trophy animals that deer hunters gush about after they see a fleeting glimpse of them in the fall woods.