What we've got here is a tule elk.

This one is an alpha-bull.

He lives on the northern California coast.

And like other alphas, he's got a harem: a group of females - known as cows - that he's trying to keep all to himself.

How did he get all these females?

He used that crown of bones on his head.

His antlers!

They're a warning to other bulls.

"Try to mate with my cows?

I'll do to you what I'm doing to this bush!"

When his warning doesn't work, he uses his antlers to fight off the competition.

Antlers are a big and expensive weapon.

Expensive because he has to use a huge amount of energy to grow a new set of these every single year.

Don't confuse antlers with horns.

Horns stay on an animal all its life.

Antlers fall off and then come back.

Antlers are bones that grow right out of an animal's forehead.

It all starts with these little knobs called pedicles.

Elk, and their relatives in the cervid family, like moose and deer, are born with them.

But in most species pedicles only sprout antlers in males, because antlers require testosterone.

The little antlers of a young tule elk, or a reindeer, are called spikes.

Every year he'll grow a slightly larger set, until he becomes a "senior" and the antlers start to shrink.

While it's growing, the bone is hidden by a fuzzy layer of skin and fur called velvet that carries blood rich in calcium and phosphorous to build up the bone inside.

The calcium comes from all the grass the males eat.

When the antlers get hard, the blood stops flowing and the velvet cracks.

That's what's happening to these reindeer.

(Reindeer grunts) The velvet dries.

It gets itchy.

Males scratch like crazy to get it off.

From underneath emerges a clean, smooth antler.

You might think the bigger the antler, the better to get a mate.

But there are limits.

He's carrying almost 20 pounds on his head.

If his antlers were any bigger, he wouldn't be able to move as fast.

This is why once the mating season is over and the bull no longer needs its antlers, the testosterone in its body drops and the antlers fall off.

This sounds like a waste, but it isn't.

The antlers return to the land.

Small animals nibble on them for their minerals - all part of a big nutrient-recycling scheme.

And next year, the elk will grow a new set of antlers, and the cycle will start all over again.

Why is this park ranger taking the antler away?

Because he doesn't want you to take it.

He'll break this one into small pieces and scatter them in the grass.

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