naturalist

noun

natural historian, life scientist, wildlife expert;

biologist, botanist, zoologist, ornithologist, entomologist, ecologist, conservationist, environmentalist, preservationist;

birdwatcher;

North American birder;

informal twitcher.

easily confused words	naturalist or naturist?
Unwary naturalists might be embarrassed to come across naturists when they were looking for specimens. Despite their similar spelling, the two words have quite different meanings: a naturalist is someone interested in or knowledgeable about natural history, while naturist is a less common term for nudist.

naturalist Oxford Dictionary of English