A female rat can mate as many as 500 times with various males during a six-hour period of receptivity—a state she experiences about 15 times per year. Thus a pair of brown rats can produce as many as 2,000 descendants in a year if left to breed unchecked. (A rat matures sexually at age three to four months.) An average rat's life span is two to three years, and to add to that a lot of the young females have now had litters of their own!! :-)
We get rats in our back garden occasionally. Freaks me out. And we've also had a little mouse in our garage, but he loved the peanut butter in the trap! Made a right mess of a very old sleeping bag which Mr. Chox used to cover some of his stuff in the garage!
melv I can understand your reluctance to put poison down, we felt the same. I had to eventually, it sorted the problem. Remember that rats do learn feeding and behavioural patterns from each other. So although you are managing to trap a few, the blighters have already passed on the habit of, seek food in melv's shed, to the next generation.