My larger issue is how could a language not differentiate between mountain climbing and hiking? Wouldn't the better term for hiking be 도보 여행 or do Koreans really just usually call it rock climbing (which requires rocks, much better physical fitness, proper clothes and typically equipment)?
고슴도치 has an interesting etymology. It’s a combination of 고솜+돝 with intermediate forms (oldest to most recent) 고솜도ᄐᆡ, 고솜도틔, and 고솜도티. The 돝 meant “pig” in Middle Korean so in a way it kind of resembles the English “hedgehog.”
돝’s later descendants are preserved in some dialects as 암톹 (sow/female pig or 암퇘지 in standard Korean) and 수톹 (boar/male pig or 수퇘지 in standard Korean). The ㅌ initial consonant within each compound is an artifact of a prior sound merger: ㅎ+ㄷ→ㅌ. 아ᇡ (female) and 숳 (male) were used to derive animal names according to sex. Hence 아ᇡ+돼지 yields 암퇘지, and 숳+닭 yields 수탉 (rooster). 돼지 itself—interestingly—also derives from 돝.
등산하고 있어요 is present progressive, so the correct translation is "hiking" rather than "hikes".
No one expects you to repeat these sentences to anyone, but it's useful to see how the sentences are structured and to learn the grammar points so that when you come to make your own actual sentences in Korean you will know how to structure them.
What I remember from English lessons there was a certain rule that adverbs like "always" or "often" + progressive are used for giving others the impression that described thing or phenomenon is very annoying. I haven't used my rusty English for several years so maybe I am wrong. If so, I apologize for the confusion....