"Elephants are protected animals."
Translation:Gajah adalah hewan yang dilindungi.
"Hewan" is used mainly for scientific/academic contexts whereas "binatang" is for daily conversations, according to native speakers.
The original sentence with "adalah" and "hewan", therefore, suggests that it might be quoted from an official report by an animal protection NGO. "Adalah" is inserted for formal sentences, particularly when you define the meaning of the subject. The connotation of the sentence is "elephants are categorized/registered as protected animals (by an authority)".