Why do deer shed their antlers in the winter after spending so much time, energy and nutrition growing them each spring and summer?

 

“Scientists have pondered it for years, and we still don’t know exactly why,” said Iowa biologist Dr. Mick Hellickson, who points to a couple of theories.

Some scientists believe that deer shed their antlers so they’ll have the potential to replace damaged racks. If a buck had to live his entire life with snapped tines or a broken beam, then he couldn’t fight his rivals or posture for does; so he grows a shiny new set before the breeding season each year.

A second theory suggests that bucks shed old antlers and grow new ones 10 to 20 inches larger the following year to keep pace with their increasing body weight and girth as they mature.

Related: 5 Best Places to Find Deer Shed Antlers

why do deer shed their antlers

Photo: John Hafner

After the previous fall’s rut, a buck’s decreasing testosterone levels can cause an abscission layer to form between the antlers and their pedicles. As this connective tissue gradually dissolves, antlers begin to get loose and eventually fall off. Bucks may cast their racks from late December in northern latitudes through March and April in southern locales. It varies across North America, but most antlers fall off in January and February.

Cold weather, snow, altitude and food availability can influence when deer shed their antlers. If your area had a noticeably early rut the previous fall, a buck’s testosterone will decrease earlier, and some may cast their racks two to four weeks earlier than normal. In the North, a severe winter may cause stressed deer to shed earlier than usual.

According to Hellickson, the specific time a buck drops his antlers may be determined by its individual antler cycle. This cycle is independent of other bucks in the area and is probably centered on each animal’s birth date. As a rule, older bucks shed earlier than younger ones.

Interestingly, some people once believed that bucks withdrew to secluded places to shed their antlers away from does and rival bucks, thus avoiding loss of virility in the public deer world. But that is probably an old wives’ tale. Modern-day biologists say deer are likely unaware of when and where they’ll lose their headgear. Old antlers are apt to plunk off a deer’s head anywhere.

Antler’s Grow Faster Than Superman Heals (Potentially)

why do deer shed their antlers In April, as the days get longer and the light increases, new antlers begin to grow from buds that form on the pedicles on a buck’s head. Within a month, main beams and brow tines typically begin to sprout and split off. A month or so later, second and third tines will form.

Throughout early summer, the fledgling racks grow fast and furious. Antler tissue is the fastest growing tissue known to man. Beams and tines may grow a quarter-inch or more per day. This process is driven by a buck’s hormones and the photoperiod of the days.

According to Missouri scientist Dr. Grant Woods, a buck’s rack will show most of its points by mid-June, though tine length is typically less than half developed at this time. Most of the beam length will grow by late June.

Those are the general rules, but Grant pointed out that the growth of individual racks can vary.

“Some bucks will show a lot of antler growth early, while others seem to add a bunch to their rack during July,” Woods said.

Bonus: Antler Trivia

  • A Buck’s Skeleton Contributes Minerals. Antlers consist of bone and mostly calcium, phosphorus, magnesium and other minerals. Although some of the minerals needed for antler growth are taken from food, scientists note that a lot of them are sucked from the buck’s skeleton, which may cause him to develop osteoporosis during the summer. Setting mineral licks for the deer can help.
  • Tines As Neon Signs. Throughout June and July, velvet antlers have a complex system of blood vessels that causes them to be hot to the touch. “There is so much blood carrying protein and minerals to a buck’s antlers that even small antlers are easily detected by thermal imaging devices,” Woods noted. “Tines show up like neon signs when flying over with thermal cameras in summer.”
  • Velvet Radar System. Tiny hairs on the velvet stick out and make the antlers look bigger than they are. The hairs act as a radar system so the buck won’t bump into trees, fence posts, etc. and damage his soft antlers.
  • Bucks Have Insect Repellent Too. Sebum, a semi-liquid secretion on the hairs, gives the velvet a shiny look. Sebum also acts as an insect repellent to keep biting flies off a buck’s rack and face.

Turn Down the Lights. Shed the Velvet. Cue the (Tree) Rubs.

By mid-August, most of the antler growth for the year is done. By September 15, bucks shed their velvet. The cue for antler hardening and velvet shedding is the change in photoperiod caused by decreasing daylight and increasing darkness.

Velvet shedding typically only takes a couple of hours, though it is not uncommon to see a deer walking around for day or two with bloody velvet tatters. Bucks have also been known to turn their heads and peel or even eat the dry velvet off their new racks.

At this point, the tree rubbing begins. With their new crowns gleaming, mature bucks are ready to breed for the next three months until their testosterone fades and the fascinating antler cycle begins all over again.

Related: 5 Tips For Realistic Antler Rattling

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