We at Weird Animal Question of the Week got a bit heady recently looking at photos of awesome animal headgear and took the author’s prerogative to ask, “What are some different types of horns?”
Horns evolved independently in many animals to meet similar needs—first as weapons, and then as defenses against rivals, says Don Moore, director of the Oregon Zoo in Portland.
Horns likely initially inflicted body blows, but became larger and more elaborate as they absorbed blows to the head. This strategy led some animals, like pronghorns, to essentially wrestle (watch a video), whereas others, like sheep, ram their opponents.
Horns can also communicate power—big ones, for instance, may identify a herd's dominant male so that newcomers can avoid fighting him and risking injury, Moore says.
Male horns may also attract females looking for the strongest mate, though in most ungulate species, females also have horns, says Patrick Bergin, chief executive officer of the African Wildlife Foundation. The beautifully striped bongo is one example, he says.
Species with horned females are usually large and live in open areas, making it difficult to camouflage themselves and likely driving the evolution of their weaponry. They're often species in which females fight each other for territory, according to a 2009 study.
In particular, Africa's “diverse ecological niches” sustain a huge variety of hoofed animals with many different horns, Bergin says.
They range from the jackrabbit-size dik-dik, with three-inch (eight-centimeter) horns, to the giant eland, whose curling horns can reach nearly four feet (just over a meter).
It's not always clear whether horns help African animals in their habitat, but scientists have some clues. The nyala, for instance, may use its spiraled horns to move brush aside and help the shy creature hide.
The red forest buffalo’s horns are "smaller, tighter to the head, so they can move through the forest” easily, Bergin says.
That's not the case for the Cape buffalo, whose grassland lifestyle allows for big, curved horns. The horns sometimes grow so large they fuse in the center, creating “one big solid plate of horn” called a boss. It can be quite a defense in a fight with a lion, Bergin adds.
Horns differ from antlers in that they’re permanent, fused to the skull, and covered with keratin, the same material that makes up our fingernails. Antlers are shed annually and are made only of bone.
Rhinoceros horns are the exception: A recent study found they are made of keratin with deposits of calcium and melanin in the core, instead of bone. The horn gets its shape when the animal rubs it, softened by sun exposure, on the ground.
Also, a rhino horn can regrow—depending on how much is lost—while other animals' horns can’t. (Also see "South Africa Just Lifted Its Ban on the Rhino Horn Trade.")
But when the animals die, their horns don’t always go to waste. A very specialized insect native to Africa, the horn moth, “lays its larvae in the horns of these deceased animals,” Bergin says.
The bugs then spin silken tubes and dine on the horns' keratin coating.
Who wants keratin cake?
There are so many horned animals—what are some of your favorites that we missed?