Why do female reindeer grow antlers?

Both male and female reindeer grow antlers, but that makes them unique in the deer world. Why are reindeer different? Biologist Craig Roberts has the answers.

Female reindeer with antlers, alongside her calf on Arctic tundra © Ken Canning / Getty

Males of almost all deer species grow antlers, used to battle for females.

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But reindeer are the only species in which the females also grow antlers, and an explanation can be found by looking at bovids, a closely related family including antelopes, goats and sheep.

Adult female reindeer with antlers in velvet (Rangifer tarandus), walking across upland moor, Cairngorms, Scotland, UK.
Adult female reindeer with antlers in velvet (Rangifer tarandus), walking across upland moor in the Cairngorms, Scotland.

Many female bovids have horns, used to defend food or territories from other females.

In exactly the same way, female reindeer use their antlers to defend food in small patches 
of cleared snow. Those with the largest antlers tend to be socially dominant and in the best overall physical condition.

Unlike horns, antlers are shed each year. In males, this happens in late autumn, after the rut.

Reindeer are fantastically well adapted to their cold habitats. Want to find out how? Then check out this article we wrote all about it – 6 ways reindeer are adapted for extreme cold

Photo © Dmitry Chulov/Getty

Reindeer in natural environment, Tromso region, Northern Norway.

Females retain their antlers until spring, because access to food is critical during their winter pregnancy. Some scientists therefore argue that Rudolph, who is universally depicted in late December with intact antlers, is female.

In fact, most of the reindeer used to pull sleds are castrated males – they are easier to handle, and have antler cycles similar to those of the females.

A Christmas reindeer with baubles in its antlers looking at a small Christmas tree in the snowy Arctic tundra
Rudolph the red-nosed reindeer was probably either female or a castrated male. © Per Breiehagen/Getty

Not all females have antlers, however, because growing them costs a lot of energy. In habitats where food is scarce or of poor quality, antlerless females dominate.

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