Why do animal horns come in so many shapes and sizes?

DW (English)

Sheep, cows, rhinos and antelope are just a few of the animals that have horns. But they vary a lot between species. Why is that? This week’s viewer question comes from Sofia R. in Colombia.

Transcript

00:00 Why do the horns of large herbivores come in so many shapes and sizes?

00:09 First of all, not every animal with fancy headgear has horns.

00:13 Deer and their relatives have antlers which are made entirely of dead bone.

00:17 They're shed every year and then regrow.

00:22 Horns by contrast grow throughout an animal's life.

00:26 The rhino family has one kind of horn made only of super hard keratin.

00:32 The bovid family has a different kind of horn.

00:36 Bovids include goats, sheep, and antelope, and their horns share common features.

00:43 The core is made of living bone interlaced with blood vessels all covered with a tough

00:47 coating of keratin.

00:49 It's the same substance that makes up our own hair and fingernails.

00:55 The shape of the horn is believed to play a role in the regulation of body temperature,

01:00 especially in the heat-sensitive brain, as scientists have documented on infrared thermal

01:05 images.

01:08 The top of the head on cows with horns stays cooler than in cattle whose horns were removed.

01:16 In more temperate regions, cattle horns tend to be shorter and lightly curved and covered

01:21 with a thick layer of keratin.

01:25 In the tropics though, cattle tend to have big, sweeping horns.

01:30 Their large surface area can dissipate excess body heat without water loss.

01:37 The same holds for the upright horns common to gazelles and many other antelope.

01:44 Their horns are covered by a thin keratin sheath and have a cooling network of blood

01:48 vessels that extend to the very tips.

01:51 It's an adaptation that isn't well suited to the cold.

01:54 When they're kept in zoos in cooler climates, antelope from Africa can even get frostbite

02:00 on the tips of their horns.

02:02 (upbeat music)

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