Intelligent mammal trouble

As a couple, the word I associate with my parents most is "bicker". This trip home I have constituted myself the impartial judge against whose ruling no appeal can be made. So far this morning I have decreed that yes, it is unreasonable of my mum to try to dust the oven while my dad is making Sunday dinner; and that no, my dad should not put his used tea leaves down the sink. We were discussing the latter while standing by the kitchen window, looking out over the back garden; we were interrupted by the appearance of an endangered mammal in the pond. Most of our back garden proper is a pond, my father's work. Every time I come home he has altered the configuration of weirs and ponds in the stream which leads down to it. It is very much a wild pond, with a swamp at one end planted with bog weeds, and it has frogs, newts and toads, plus all sorts of strange bugs. Last time I was home I looked out of my bedroom window before I had even got up one morning and there was a fat kingfisher perched over the shallow end.

The endangered animal swimming across it was plump and fluffy, and out to retrieve the floating fish food. It was a rat; it made me exclaim, ah, look how lovely it is! The reason it is endangered is that rats found a way to get into the walls of our house. My parents, being enlightened creatures who would never reject anything out of hand for conventional reasons, don't in the least mind there being rats living by the pond, but they don't like the idea of them inside the lining of the walls, which is sensible given the chaos they could wreak on the cables and piping there. The problem is that, as I can attest from my experience of keeping rats as pets, once an idea has got in their head it is very hard to make them forget it. My parents comprehensively closed the hole they found with wire netting, that spray filler stuff, a slate and some concrete, but still the rats managed to open it again, and now my parents think there may be another hole. They bought a thing that makes a high-pitched noise which rats apparently dislike, though of course they've had to turn that off while I'm at home with my tame rodents (Lilian, Muesli and Yaffle). And they have a humane trap in which they catch occasional (very annoyed) specimens; they then take them off to our furthest away field, where they join the ex pat rat community, presumably reminiscing about the good old days by the pond. (Unless, they just get on with their lives.)

But if they can't stop the rats getting in the walls then as a last resort they will call in an exterminator. This saddens me, obviously, though I can see what they mean. It's part of what's fundamentally wrong with life. The other day the subject came up of Ph.D.s and whether they're something to be proud of -- and I realised that the greatest achievement of my life so far is stopping my first rats, the late lamented Izzy and Aggy, from getting inside my sofa. After a huge number of attempts I eventually managed this by covering the entire frame of my sofa except for the cushions in chicken wire. I expect that my parents will not be able to do this to the whole house, so the rat swimming across the pond to collect fish food is probably facing an uncertain future.