Those Things On Their Heads
In our modern language usage, some terms or words may be incorrectly applied when describing an item. For example: some people do not always distinguish between horns and antlers where they incorrectly refer to all animal headgear as horns. Antlers and horns are very different in a number of ways and these variations are the result of millions of years of evolution and adaptation for the animal species to live a healthy life in the environment they occupy.
Bovids, or members of the horn-bearing group of animals versus cervids, or members of the deer, antler-bearing group of animals.
Photo left to right: Mountain goat, bison, moose, caribou.
Credit: L.Caskenette & J.Paleczny
Headgear has influenced many aspects of some species and how they conduct themselves through the year; including the obvious breeding cycle but also their comfort in the heat of summer and how they communicate and identify themselves visually.
Let’s begin with construction materials: Horns are made from keratin- the same material as your hair and fingernails- whereas antlers are made from bone. Horns are a two-part structure. An interior portion of bone (an extension of the skull) is covered by an exterior sheath grown by specialized hair follicles called keratin.
Horns grow from the base where it attaches to the animal’s skull, antlers grow from the tips. Antlers are grown only by males of the deer species except for Caribou where females grow lightweight antlers, an adaptation for their grazing in snow for lichen. Horns are present on both male and females of most horned species with the males typically having larger horns than the females.
Bovid family of animals have horns and both females and males with grow these horns. Typically female horn growth is smaller than males. Sexual selection plays a role here for large displays in both horn and antler bearing animals.
Perhaps the greatest difference between horns and antlers is that antlers are shed and regrow each year, where horns are permanent and remain and grow with the animal for all its life, or until they get broken off. Once they are broken, they do not grow back. The animal will carry a damaged or missing horn for the rest of its life. Antlers also factor into the breeding cycles of the males who employ them to demonstrate their virility and to impress the females.
Antlers too may become broken or removed completely due to carelessness or fighting. These will grow back, but not right away. The animal must wait for the annual antler shed-regrow cycle for that year to conclude, usually in mid-winter before a new antler will form during the next year’s cycle, this may cause the animal to be without an antler for up to a year.
Horns appear to form earlier than antlers on younger animals such as goats or bison, where Mountain Goat kids will be displaying small pointed black horns within a few short weeks of its birth, while antler buds appear at several months or so after a calf or fawn is born. But once they are in place and growing, they grow quickly.
Left to right: Mountain goat kids show horn formation, easily seen against the white; Watson the moose shows nubs of antlers developing in his first winter of life in 2019. Bison calves also show horn development early on in life.
Antler is the fastest growing tissue of any mammal on the planet. With a healthy diet and high caloric intake, a moose can put on as much as a pound of antler in a single day. In the scope of just eight months’ growth, moose antler can grow from tiny buds as big as your thumb to gigantic antler racks measuring up to six feet across or 1.8 meters from tip to tip. A large moose’s antlers can weigh up to forty pounds or nearly 20 kilograms on average. Some very large moose antlers may weigh up to 75 pounds or 35 kilograms.
Source credit: Alaska News Source
Back to construction for a moment; another key difference between horned and antlered animals is how the physiology of horns and antlers differ.
Horns have a central, conical bony core or cornual process that grows out from the frontal bone of the skull. On close examination of a horn you will see what appears to be layers of horn material (keratin) growing a new layer at the base which will grow longer over time and become thicker with subsequent new layers of keratin forming as the animal ages.
After 6 months of age, the bone becomes hollow and the space within it is continuous with the frontal sinuses. The surface of the bone is rigid and porous and is covered with an internal surface which keratinizes and forms the protective covering of the horn. The new horn produced at the base is soft and often transparent giving the horn a glossy appearance. Horn growth function is similar to how the cuticle on your fingers and toes produce the nails.
Source credit: Talmudology
Antlers however attach to the animal’s skull between the eye and ear at a place called the pedicel where they will grow to full size for that year over about eight to ten months. The antlers separate from the skull at the point of attachment, the pedicel.
Antlers separate from the skull at the pedicel, typically in the winter months.
The antler side is called the corona and forms a bone to bone connection with the pedicel on the skull that is remarkably strong until the its time to shed that year’s antlers. There is a chemical influence when the animal’s hormones change following the rut and seasonal progress that causes the bone between the corona and the pedicel to dissolve where eventually it weakens enough that the skull can no longer support the weight of the antler and it falls off. Both antlers may fall off at the same time, but it is common for both antlers to fall off over a couple of days.
Horns are mostly hollow, white antlers are made up of less dense, sponge-like bone called the trabecular that has been highly vascularized during formation allowing blood to flow to the tips of the antlers to facilitate their growth. Antlers require blood to grow while horns do not.
Credit: Wildlife Online
While antlers are covered in velvet, they are also engorged with blood which provides another important benefit besides growing the antler. As animals do not perspire or sweat in any way, they must expel excessive body heat by panting as many animals do. Antlers perform like radiators where body heat is expelled by the blood-filled antlers.
Ears of most deer species shed the fur and hair off them in the warmer months so they too can dissipate body heat. If they would let you, you could take the pulse of an antlered animal by finding a blood vessel on their fuzzy antler and placing your fingers on it to feel the beat of his heart. Don’t try this at home…or anywhere else.
Both horns and antlers have also been used by people since prehistoric times for tools of various kinds. The hollow nature of horns has made them desirable for spoons, scoops and hand shovels or scrapers while the strength and hardness of antlers has often found them to be the material of choice for making hunting points for spears and arrow heads. Antler has also been a popular material for handles of tools like knives and axes.
Creativity and need, guided the early peoples to adapt and modify both horns and antlers for a wide variety of tools and other purposes to better their quality of life. They have often been used to make buttons for clothing or ornamentation. Antlers have been carved into needles for sewing of clothes, shelter and similar products, Horns were popular as gun powder containers as they would prevent the powder from getting wet and were easy to carry and measure the appropriate amount of powder into the firearm.
Yukon art Hints of Easter by Faye Chamberlain, 2021. Yukon Permanent Art Collection.
Both antlers and horns provide important functions for the animals that grow them so they may live healthy, secure lives. Their headgear has also influenced many of their social behaviors that have developed and evolved over the centuries. These include mating rituals and protective activities against potential predators.
Most of us have seen sheep rams rearing up on their hind legs and pounding their horns against another ram in courtship competitions, but they may use their horns to communicate in less violent ways. Rams may interlace their horns and gently rub ear to ear as a form of communication that we can only guess what it means.
Antlered animals also employ their antlers as a means to communicate for example when two young bulls will use their antlers to joust or push each other around like a game of reverse tug o war.
Antlers are also a means of displaying size and age which will determine their social order of who is dominant and who is subordinate. From a distance the size of the antler rack quickly displays the animal’s placement in the local social order, typically around the breeding season or rut when many male moose may gather in an area for an opportunity to breed with cow moose drawn to the area by pheromones carried in the wind.
Bulls with smaller antlers will size each other up based on their antler racks and determine their chances of winning a fight with a larger bull.
Animal headgear serves a number of important benefits for the creatures that grew them. Humans have also found inventive and beneficial uses for both antlers and horns once the animals are finished using them. Humans often use antlers and horns for tools, but they can also be transformed into wonderful works of art. Nature provides.
Doug is one of the Interpretive Wildlife Guides here at the Preserve. An avid angler and hunter he has a broad knowledge of Yukon’s wilderness and the creatures that live here. With a focus on the young visitors to the Preserve, Doug takes the extra time to help our guests to better appreciate the many wonders of the animal kingdom here in the Yukon.
I learned a lot from this very interesting article. Thanks and keep up the good work.