Question: Is a 'big-horn sheep' a 'ram'?

[B]Question: Is a 'big-horn sheep' a 'ram'?

A ram is a male sheep.

A male big-horn sheep is called a ram, as is any other mature male sheepy thing. But when does a goat turn into a sheep.
What's a group of rhino's called again?

Ok, I had my brain on stand-by mode while I was watching Animal Planet. Thanks.

A flock of rhinoceros.