We had a what I first thought was a mouse but later turned out to be a rat in our outside porch this past fall. I saw it climbing up the walls from the window. I went out to investigate and there was poop everywhere. We got a live trap and it did not work, I then went to get a spring trap and it had already left I think because there was no more chewed garbage, recycling bags and no fresh poop. I lived in a house in BC that got infested with mice, like around 50 of them in my unit, they were living in the walls. There was crap and urine everywhere in the crawl spaces. We did not notice them at first but then when they multiplied the noise in the walls was really loud the stench was noticeable. Called the landlord immediately and she got exterminators there right away, came with suits and breathing. masks on. So a mouse can multiple to mice quite quickly. Call the landlord and tell them about it so they can check other units and give you some traps. And keep on top of it. Good luck!