After the breeding season, the deer shed their antlers. This occurs because special cells osteoclasts break down the bone where the pedicle meets the antler. The antler is then weakly attached and can fall off. In many deer species, the next set of antlers will begin to grow back shortly after the old set falls off. For most deer, antlers grow in the spring and summer and reach full-size in the fall.
Then in the winter the antlers fall off. This is true of the red deer, fallow deer and white-tailed deer at Fossil Rim. However, the axis deer do not follow this seasonal pattern and antler growth varies among males within the species. Horns are structurally different from antlers and are permanent they do not fall off and regrow like antlers.
In antelope, cattle, goats, sheep and other members of the family Bovidae, males have horns, and in many species females also have horns.
Horns consist of a bony core covered by a keratin sheath. Keratin is the same protein that fingernails and hair are comprised of. Also unlike antlers, horns do not branch; but horns do vary in size and shape depending on the species.
They can be straight, curved or spiraled in shape and can be smooth or ridged in texture. Males have thicker horns and use them for fighting and competition over females. Both the males and females have the horn or antler because they both use them, and for similar purposes. That is not particularly enigmatic.
It is also not hard to explain why in the vast majority of large cattle, antelope and deer species males and females are dimorphic that is, males and females look different in this trait, with only the males having the big appendages on their heads. In most of these species, males compete with each other, either in direct male-male competition or using a more show-off strategy to impress the females, in which the horns or antlers play an important role. What's harder to explain is this: In a small number of these large species, where the males compete over females, why do females also grow horns or antlers?
One early theory suggested that females in larger species could use these appendages for anti-predator defense. In other, smaller, species the females are better off hiding or running away. In my personal experience with wild Cape buffalo, this makes sense. On many occasions while working in the Semliki Valley in the Congo, I encountered small herds of female buffalo with their young. Animals Wild Cities Wild parakeets have taken a liking to London.
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Science Coronavirus Coverage What families can do now that kids are getting the vaccine. Magazine How one image captures 21 hours of a volcanic eruption. Giraffe horns are paired, short, unbranched, permanent, bony processes that are covered with skin and hair. They differ from other artiodactyl horns in that they do not project from the frontal bones, but lie over the sutures between the frontal and parietal bones. Giraffe horns begin as cartilaginous structures in the fetus and may not fuse to the cranium until the animal is 4 years old.
Horns are present in both sexes of giraffes and even on newborns. Rhino horns differ from true horns because these horns have no core or sheath. They are made up of multitude of epidermal cells and bundles of dermal papillae, extensions of the dermis.
Cells from each papilla form a horny fiber similar to thick hair. These fibers, which are held together by the mass of epidermal cells, are not true hairs. True hair grows from follicles that extend into the dermis, whereas rhino horns grow from dermal papillae which extend up into the horn.
The rhino horn is situated over the nasal bones. In species that have two horns, the second horn lies over the frontal bones. Rhino horns commonly curve posteriorly.
Pronghorn antelope, in the North American family Antilocapridae , have distinctive upright horns. They differ from the horns of bovids in two important respects. First, they are branched. Each has a short, posteriorly-directed branch near the base, and a short, anteriorly-directed hook near the tip. Second, while the horns consist of a bony core and keratinous sheath like those of bovids, the sheaths are shed annually.
In bovids, the sheaths are always a permanent part of the horn.
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