5 Reasons Bucks Have Antler Growth Deformities

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Have You Ever Killed an Abnormal Buck?

I barely noticed the buck’s limp as it walked toward my treestand at a pace steady and quick enough that if I didn’t grunt him to a stop, I might have missed my chance. But I did notice one side of his rack seemed a little “off.” I was already drawn and when my sight pin found vitals I released an arrow. The buck raced off in a wide arc, falling some 70-plus yards away.

Walking up on the fallen buck, I was curious to see the left side of his rack, which I figured might just be a typical fork, or even a spike. It was a fork, but the beam was oddly twisted and skewed out to the side rather than forward. That seemed a little odd, but I was really rocked when I rolled the buck over and realized his back, right leg was entirely missing below the second joint. The deer had apparently suffered some type of injury, but the stub was now healed over. That was just one of several antler growth deformities I’ve encountered over my years as a hunter and wildlife biologist.

Antler Growth

Antlers are among the fastest-growing tissues in nature, capable of growing up to an inch (or more) per day during peak periods. The trigger for that growth is photoperiodism or changes in amount of daylight. In spring, increasing day length prompts the pituitary gland to produce growth hormones. That triggers the release of insulin-like growth factor (IGF), which ultimately stimulates antler growth. The process starts slowly, but increases as the days grow longer. 

Later, decreasing day length again plays a role, stimulating the pituitary gland to increase secretion in testosterone. This triggers a process called mineralization. Soft antler tissue is converted to bone when minerals are deposited within the matrix of cartilage and blood vessels.  Once the process is complete, blood supply to the antlers is cut off. The antlers and their velvet covering die off. Velvet comes off completely within about 24 to 48 hours, leaving dead bone of the completed rack behind. Still later, shortly after the days gradually start getting longer, there is another minor pulse of hormones that results in an abscission line between the skull and antler pedicle, and the dead antlers are shed. This occurs in late winter to early spring. And the process starts all over again.

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Damage to the PedicleDamage to the PedicleDamage to the PedicleDamage to the PedicleDamage to the Pedicle

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1 | Damage to the Pedicle

After harvesting two bucks in two days with spikes on only one side I contacted Mississippi Department of Wildlife, Fisheries, & Parks deer biologist William McKinley. He directed me to Gabe Karns from Auburn University who was researching the phenomenon of spike-on-one-side (SOS or SOOS) bucks. From a sample size of 71 such animals, Karns was able to assign probable cause to 44, 34 of which were the result of pedicle or skull trauma (likely due to fighting). Due to sample collection protocol, he couldn’t determine if other cases may have been the result of healed leg fractures, old gunshot wounds or other skeletal injuries, though previous research indicates that as a likely cause. Karns added that any damage to the pedicle, including antlers that failed to cleanly separate when shed can negatively affect antler development. The buck in the photo was aged at 9 1/2 using the tooth-wear-and-replacement method. This old buck probably sported a more typical rack through his earlier adult life.

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2 | Injuries to the Body

Most hunters know that skeletal injuries, particularly to the long bones of the legs, often result in antler deformities. The interesting thing is that the deformity occurs on the opposite side of the body from the injury. We’re not quite sure of the mechanism here but it could have something to do with the fact that the right side of the brain controls the left side of the body, and vice versa. Research has also shown that if the injury is not too severe, deformities due to skeletal injuries progressively disappear with each subsequent antler-growth cycle.

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3 | Genetic Traits

There are two major causes of non-injury-induced abnormalities. According to Kip Adams of the Quality Deer Management Association, research suggests that upwards of 50 percent of the deer in wild populations have the genetic make-up for abnormalities like sticker points, drop or forked tines, webbed or palmated beams and the like. However, those genetic aberrations often don’t manifest themselves until later in life. We just don’t see them in that high of a frequency largely because the deer never live long enough to express them.

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4 | Age

Sometimes age alone is enough to cause abnormalities. Wild deer seldom live long enough to experience it, but over time, their bodies simply start to deteriorate. And as those of us who are getting up in years know, it often starts with the bones. It may begin with simple things like sticker points on the bases. Nonetheless, antlers can become increasingly more gnarly. 

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5 | And More

Yet another curious abnormality involves deer that retain velvet-covered antlers into the fall, sometimes referred to as stags, and there are several causes. The most common is some type of injury or malady to the testes. The deer gets an initial surge of testosterone, which stimulates antler growth as the days grow longer. But the second, end-of-summer surge never occurs, so the antlers don’t mineralize and die.

A more unusual example of this is the antlered doe. For a variety of reasons, female deer sometimes experience unusually high testosterone levels and will grow antlers as a result. According to Maine Department of Inland Fisheries and Wildlife Former Deer Biologist Gerry Lavigne, “In most instances, doe antlers are spikes, which remain covered with velvet.” And they’re not as unusual as you might think. “Of the 2,000-plus hunter-killed does MDIFW biologists examine each year, five to 10 does are observed to have antlers,” says Lavigne.

Again, the specific mechanisms are complex and varied but antlered does typically don’t shed velvet or antlers. Though rare, “does” with larger, polished antlers do occur. They’re not does that simply identify as bucks. These deer often have reproductive organs of both sexes and are abnormalities in and of themselves, termed hermaphrodites or pseudo-hermaphrodites.

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