Haspiror

It slams foes by sharply uncoiling its rolled ears. It stings enough to make a grown-up cry in pain.

When it senses danger, it perks up its ears. On cold nights, it sleeps with its head tucked into its fur.

Its ears are always rolled up. They can be forcefully extended to shatter even a large boulder.

You can tell how it feels by the way it rolls its ears. When it’s scared, both ears are rolled up.

By extending its rolled-up ears and striking the ground, it can bound so high it surprises itself.

Its arms and legs are weak, but when it rolls its ears up tight and then unleashes them with its full force, it can smash boulders to dust.

The reason it keeps one ear rolled up is so it can launch a swift counterattack if it’s attacked by an enemy.

If both of Buneary’s ears are rolled up, something is wrong with its body or mind. It’s a sure sign the Pokémon is in need of care.

Buneary can attack by rolling up their ears and then striking with the force created by unrolling them. This attack becomes stronger with training.

My hypothesis as to why Buneary rolls up its ears is that its hearing is far too keen. I surmise that the Pokémon protects its hearing by limiting the sound that may enter its ears.