Do those high pitched plug in things work on rats does anyone know?
No, they don't. We got them when we had mice, and they worked a treat.
Then rats decided to use the space under the kitchen floor as a maternity hospital.
They weren't deterred in the slightest by the ultrasonic thingies.
Council rat man was brilliant, showed me exactly where they were getting in (a tiny bit of mortar missing in the outside wall) and explained that they were coming in to have their babies because it was so cold outside (winter of 2010). He told me that once the ratlings were big enough, they would leave.
My terriers had alerted me to their presence by their determination to dig up my kitchen floor to get at the fuckers. I might never have known otherwise. The rat man explained that the dogs would also let me know when they had buggered off again, and we could then repoint the entry point and stop them returning. He put poisoned bait in the loft, in case they'd got up there, but they hadn't.
His advice was sound and they've never come back, although we find a dead one in the garden every now and again, courtesy of surviving dog. He was also very reassuring, and told me that there was hardly a house in the area that hadn't had a rat problem and that it was no reflection on the cleanliness of my house.
One story he told freaked me out a bit though. (Nervous MNers should stop reading here!)
He'd been to a house that had clear evidence of rat infestation, but he couldn't find where the rats were nesting. He asked the owners if he could bring his own dog (border terrier) round to see if she could sniff them out.
She quickly homed in on where they were. They had nested behind a built-in cabin bed in a child's bedroom, inches from where the child had been sleeping!