“It’s a Jungle Out There” is also a song written by Randy Newman and used as the theme song for the TV series Monk. The lyrics allude to Monk’s plethora of fears and warn that some degree of cautiousness and attention is necessary to stay alive, given everyday life’s many dangers.
Another idiom that uses the term the jungle as a metaphor for a dangerous and threatening environment is the expression the law of the jungle in reference to a world where the the strongest will survive