What’s the difference between horns and antlers?

Bone vs keratin, branched vs unbranched, shed vs permanent - Ben Garrod explains what sets antlers apart from horns.

A red deer stag photographed in Glen Etive, Scotland. © Billy Currie/Getty

What are antlers?

Antlers are paired, branched structures that are made entirely from bone and are shed annually. Developing antlers have a high water and protein content and a soft, hair-like covering known as velvet, which comprises blood vessels and nerves. As a result of hormonal and environmental changes, the antler ossifies – the growing, spongy bone is converted into harder, thicker lamellar bone – before the velvet falls away altogether. Antlers are usually only present for a few months before being shed and, apart from reindeer, only occur in males.

Reindeer (Rangifer tarandus) adult female, antlers in velvet, walking across upland moor, Cairngorms, Scotland, UK.
A female reindeer with antlers in velvet, walking across the Cairngorms, Scotland. © Mark Hamblin/naturepl.com/Getty Images

What are horns?

Horns are unbranched, two-part structures with a bony core and covered by a keratin sheath (the same material found in human hair and nails), which grows from specialised hair follicles. Horns are a permanent feature and, in many species, grow continuously.

A greater kudu bull, with twisting horns. © Alun Marchant/Getty
A greater kudu bull, with twisting horns. © Alun Marchant/Getty Images

Pronghorn antelopes (below) are the exception among horned species, having branched, upright horns with a sheath that is shed annually.

Pronghorn buck. © S.B.Nace/Getty
Pronghorn buck. © S.B.Nace/Getty Images

Antlers and horns also have different functions. While antlers are mainly used for mate selection during the breeding season (either to attract females directly or to deter rival males through display or combat), horns are generally used for social dominance, territoriality and anti-predator interactions.