Translation guide
The small spiny mammal. In Japanese, the default word is ハリネズミ. There is also a less common literary term ヤマアラシ, but it can also mean 'porcupine', so learners should be careful.
Referring to the small insectivorous mammal with spines, often kept as a pet.
The standard word for 'hedgehog'. Literally 'needle mouse'. Used in everyday conversation, books, and media.
I found a hedgehog in the garden.
Literally 'mountain storm'. Can mean 'porcupine' or 'hedgehog', but in modern Japanese it usually refers to porcupines. Using it for 'hedgehog' may cause confusion. Found in older literature or poetic contexts.
Often understood as 'porcupine'. Use ハリネズミ to be clear.
ハリネズミ is the clear choice for 'hedgehog'. ヤマアラシ is ambiguous and often means 'porcupine'. In set phrases like ヤマアラシのジレンマ (hedgehog's dilemma), it is used, but in daily life, stick with ハリネズミ.
I keep a hedgehog as a pet.
There is a concept called the hedgehog's dilemma.