Horns
|
Antlers
|
Common Function
Horns and antlers, though different, are incredibly similar. It makes sense that they would serve some of the same purpose for the animals.
Competition
Competition is violent for decorated ungulates, often involving head-butting. Sometimes, the difference in size, age, and maturity is so great that no fight is necessary. All a younger male needs to do is observe the horns or antlers of his opponent, and determine whether it is obvious who would win. Fights are not intended to injure or kill, but to establish dominance. As soon as it is clear who is superior, the female can make her choice.
Protection
All ungulates are herbivores, and fall prey to other animals. Horns and antlers are both important tools for defense against predators. Even their value as an intimidation factor is key to survival. Predators may avoid hunting an animal if its headpiece looks large enough to cause severe damage. Perhaps this is part of the reason ungulates have become so successful, widespread and diverse.
Horns and antlers, though different, are incredibly similar. It makes sense that they would serve some of the same purpose for the animals.
Competition
Competition is violent for decorated ungulates, often involving head-butting. Sometimes, the difference in size, age, and maturity is so great that no fight is necessary. All a younger male needs to do is observe the horns or antlers of his opponent, and determine whether it is obvious who would win. Fights are not intended to injure or kill, but to establish dominance. As soon as it is clear who is superior, the female can make her choice.
Protection
All ungulates are herbivores, and fall prey to other animals. Horns and antlers are both important tools for defense against predators. Even their value as an intimidation factor is key to survival. Predators may avoid hunting an animal if its headpiece looks large enough to cause severe damage. Perhaps this is part of the reason ungulates have become so successful, widespread and diverse.
Horns
Horns are found on members of the family Bovidae, a very diverse group of animals. It includes all wild cattle, antelope, and goats, as well as domestic cattle, sheep and goats. Click below to learn more about this family of animals.
The Exception: There is one outstanding species, the American pronghorn (above, bottom right), which is unique. It is the only animal with horns that does not belong to the family Bovidae, and it is also the only animal to possess horns with two prongs for which it is named. They are still horns though because they are permanent structures with an internal blood supply, and are found on both males and females of the species.
Anatomy
The first sign that a young ungulate is developing horns is just a horny bump on the skull called the horn bud, or button. From this point, the horn will continue to grow in size for the animal's entire life. In the diagram to the left, the bone of the skull is outlined in red. This bone is coated in keratin (labeled as "dead horn" in the diagram) - the same material that makes up hair and nails. You can see that the sinus cavity can even extend into the thicker base of the horn. |
Domestic Animals Without Horns
Horn Removal
The fact that almost all dairy cows on all farms are hornless causes misconceptions about horns. This is not a sign that cows (females) do not grow horns. It simply means that the horns were removed, as is common farming practice.
Polled Animals
It is also common for some individuals never to develop horns at all. These animals are called polled (because the top of the head is referred to as "the poll"). Polling occurs naturally according to the genetics of the animal. In nature, animals depend more heavily on their horns, so polled animals are much more rare in the wild.
Horn Removal
The fact that almost all dairy cows on all farms are hornless causes misconceptions about horns. This is not a sign that cows (females) do not grow horns. It simply means that the horns were removed, as is common farming practice.
Polled Animals
It is also common for some individuals never to develop horns at all. These animals are called polled (because the top of the head is referred to as "the poll"). Polling occurs naturally according to the genetics of the animal. In nature, animals depend more heavily on their horns, so polled animals are much more rare in the wild.
Antlers
Antlers are only found on male members of the deer family (cervidae) of the even-toed ungulates. Since antlers are only found on the males of these species, that makes them sexually dimorphic species (meaning the two genders have strikingly different bodies). Click below to learn more about this family of animals.
The Exception: Caribou (above, top left) are the only members of the deer family to grow antlers on both males and females. They are still antlers though because they shed annually and develop velvet.
Anatomy
Unlike horns, antlers do not have a keratin outer coating. The antler you see is truly exposed bone. While the bone of the antler is growing, there is a hairy outer skin of velvet that provides the blood supply. When the antlers are finished growing, the velvet is shed, often in a single day. Button Buck A button buck is a young male, about six months old. His first set of "antlers" are just very small, hair-covered bumps. The first set of antlers grows in at about 1 year of age. |
This chart (above right) shows an interesting correlation between both testicular volume and testosterone levels in bucks throughout the year. The surge of testosterone just before the rut is what causes the velvet to shed.
13th of September, 2014