Animals have a consistent habit of developing ornamentation on their heads for a variety of functions. In this episode, we discuss the diversity, terminology, and behavior associated with Horns and Antlers.
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A Whole Lot of Headgear
It’s very common for animals to have showy ornamentation on their skulls. Among mammals, the most diverse headgear is seen in artiodactyls. But the word “horn” is applied to a wide variety of features among a wide variety of animals, and these structures are used in a wide variety of ways. It’s a striking example of convergent evolution.
By some definitions, the only “true” horns are those of bovids, while everything else is a “horn-like structure,” although in common speech, we use the word “horn” for a whole variety of structures, even outside of artiodactyls.
Headgear has a variety of functions. They are commonly used for display, showing off to mates, signalling fellows from across the plains, frightening off predators, or intimidating rivals. Of course, they can also be used more aggressively, to fight off anyone – predator or competitor or nuisance – who gets too close. But their most famous function is ritualized combat, wherein rivals, usually males, clash heads in battles for territory or mating rights.
A History of Headgear
The evolution of horns, antlers, and horn-like structures is, unsurprisingly, very complex. Among the various ornamented animal groups, these structures have been evolved and lost many times. There are some interesting trends and patterns related to animal lifestyle and behavior. For example, bovids in open environments tend to have larger horns visible over long distances, while those in more closed forested environments often have shorter sharper horns that allow more maneuverability. And of course, large horns are common in animals with highly territorial behavior.
The evolution of antlers, particularly the habit of regrowing them every year, has been the subject of lots of hypothesizing. It might be that this highly energetic process is a strategy to ensure each year’s set of antlers is fresher, larger, and more ready for combat.
A literature review of horns and horn-like structures (technical)
Evolution of ruminant headgear (technical)
Evolution and development of antlers (technical, paywall)
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