naturalist; natural historian
A scholar who studies natural history, including plants, animals, and minerals. Often used in historical or academic contexts.
Darwin is a famous naturalist.
He collected many specimens as a naturalist.
博物学者 is the formal, native Japanese term for a naturalist who studies natural history, while ナチュラリスト is a loanword that can also refer to an advocate of naturalism in art or philosophy.
Compound of 博物 (natural history) + 学者 (scholar). The term reflects the historical discipline of natural history.