Stating the Not Obvious

As I was reviewing a course on ADA (Americans with Disabilities Act), I ran across this sentence, “Remember that dogs are *not* the only type of service animals.”

This caused me to ponder. What other kinds of service animals are there, or could there be? I thought of recent animals I’ve seen around the city lately. Iguanas. Ferrets. Pythons. What could they be trained to do?