Rat urine is actually highly concentrated, meaning less of it smells stronger than the average urine.
In contrast to its intense ammonia smell cat pee has a light vague odor that most would agree smells like stale old food. For rat’s, the opposite is true and they do not produce as much as other animals and this makes their foul-smelling post-urine leakage all that more potent. The rats also enjoy urinating on things for some unknown reason and it often will trickle down walls, leak under doors and eventually soak into carpets or floors — causing some truly tough stench problems. Often the odors associated with rat droppings are so strong they can be smelled from some distance away!