we had one in our garden prob more as they love compost bins had enviromental health out and they put posion around compost bin and they were dead within a week.
husband dug out compost bin and lined with bricks so solved rat problem (neighbours found 2 dead ones behind shed, they have a compost bin on other side of fence to ours so little ******* were having a real feast!!)
they didnt really bother the buns we keep them covered at night and rats had tended to stay around composter. we did make sure we were sweeping up any bunny droppings, sawdust, hay,straw - we usually leave it blowing around!!! so think this helped