Saturday, June 5, 2010
Fun Fact of the Day 6/5
One might be inclined, upon first glance, to look at an animal like, say, a moose and comment upon the impressive stature of it's horns. Indeed, I often hear people say things like a deer's horns, or a sheep's antlers, etc. Point being, many often make the mistake of assuming that "horns" and "antlers" are congruent and thus, interchangeable terms; or they don't know the difference. So, allow me to clear it up. The difference between horns and antlers as anatomical structures is their permanency. Horns are structures which grow from a young age in a particular animal, and remain permanent. In contrast, antlers are structures which grow seasonally, and are shed seasonally as well. Additionally, both antlers and horns can be indicators of sexual dimorphism, wherein only one sex has horns or antlers. This is more common with antlers, but some animals also have only horned males or (in rare cases) females as well. But that's beside the point, the real point is that there is a defined difference between horns and antlers. For instance, gazelles have horns. They begin to grow as juveniles, and while they do stop growth at some point, they are never shed. They are made of permanent bone, and are conjoined to the skull. Now compare this to a deer or a moose (which is actually a large deer). They, instead, have a cycle of antler growth and shedding. In winter, deer do not have antlers, males included. In spring, males begin antler growth anew, with small stubs appearing and growing rapidly into branching structures. By late spring/early summer, these knobs will grow into nearly full racks of antlers, with older males displaying a larger set of antlers each year. But these antlers are still velvety, meaning they are covered in a fizzy layer of skin and fur as blood flow continues to supply nutrients for their growth. This velvet remains present as the antlers grow through the summer. In early autumn, the antlers "dry out", as blood flow stops and they become calcified structures free of tissue. This, in turn, causes the velvet to dry up and become itchy for the deer, and they spend a great deal of time rubbing it off on trees and rocks. Finally, as September-November rolls around, the antlers on all male deer are complete in growing, and are ready for use. It is at this point that another major difference between horns and antlers also becomes apparent. Antlers are used in the fall for what is called the rut, the breeding season. In this, the males become very active and aggressive in the search for females, and they use antlers to fight with other males exclusively. Horns, in contrast, can be used for this too, but because of their permanence, they are more versatile in their applicability and can also be used for defense, or even digging or scraping. So, there you have it. Antlers: yearly structures, grown anew for reproductive competition in males. Horns: permanent structures, more wide in application.
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment