Warfarin type rat bait makes them very much in need of water and they will take all kinds of chances to seek it out. Usually, but not always, they will head outdoors for a source of water and die somewhere before returning.
Before moving here, my shop was in a former old carriage and stage coach repair shop that was almost 200 years old. A rat lived in there somewhere and was touring my shop every night after I had first moved in, obviously looking for anything that I might have left that he could eat. The first night he consumed two Macintosh apples. After that, I learned not to leave any food, not even a dirty coffee cup in the shop.
Adjacent to my shop was a photo dark room and a pottery shop within the building, and rarely used any more. Upstairs the former hay loft had been converted into a large apartment, but no one was living there. I bought him some warfarin bait and he ate several boxes of it, even tried to take one of the boxes back through a hole in the partition around a heat pipe that led to the photo dark room. He died next to the sink in the dark room. The water faucet on the sink was dripping, and that was likely his source of water. I was hoping that he had left and died outside when he stopped eating the bait, but a few days later he was changing the smell of my shop and I had to go find him. A shovel took care of removing and planting him. He was big, the biggest rat that I had ever seen, and had to weigh about 3 pounds. When he emptied several of the bait boxes before dying, I was beginning to imagine that he was dog sized, but he was more like an adult rabbit in size when I found him. Still, he was very big for a rat. After he was gone, I had my shop there for several more years before moving and never had a mouse or even another rat leave any evidence of them being in my shop. Maybe they were all afraid that he might still be there.
Charley