A perhaps surprising number of vertebrate animals from different groups have developed 'sharp things' on their heads. While it might seem that these evolved primarily for defence, the fact that in many species only the males have horns suggests that this is unlikely to be the main, or even primary, purpose. In many cases males use the horns - and I'm using the term loosely for now - in competition for mating rights. Secondary uses for food foraging have also developed.
True horns occur in two families of the huge Order of Artiodactyla, which comprises the even-toed ungulates, or hoofed mammals; one family comprises just the North American Pronghorn, the other includes cattle, various antelope groups, goats and sheep. A horn consists of a core of living bone, covered in a tough keratin sheath (keratin being a tough fibrous protein which also forms outer skin, claws, scales, feathers and hair). Interestingly most horns are curved and ridged, though they range from simple and slender to massive and complex.
|Oribi male, Ourebia ourebi, Murchison Falls National Park, Uganda. Only male Oribi have horns.|
|Waterbuck male, Kobus ellipsiprymnus, Lake Mburo National Park, Uganda. Again, only the males are horned.|
|Korrigum pair, Damaliscus korrigum, (formerly lumped with other Topi or Tsessebe species),|
Waza National Park, northern Cameroon.
|Loder's Kob male, Kobus loderi, Benoue National Park, central Cameroon.|
|Impala male, Aepyceros melampus, Lake Mburo National Park, Uganda.|
Only males have the lovely spiralling horns.
|Merino ram Ovis aries, Lake Cargelligo Show, New South Wales. |
Sheep and goats are actually taxonomically very close, and are generally described as goat-antelopes!
|African, or Cape Buffaloes, Syncerus caffer, Queen Elizabeth National Park, Uganda. |
Both males and females are horned, but the males' armoury is much more massive.
(The flying egret and Skimmer are bonuses!)
|The budding horns can just be discerned in this African Buffalo calf.|
On the other hand several other mammals - and even some other animals - have evolved pointy things on their heads for similar purposes, albeit not formed in the same way. I'll visit some of them tomorrow.