I’ll have to admit, I’ve give the in city angle some thought too. If like you say, he doesn’t move much, it would be hard to spot him there also.
Wouldn’t it be great to have a super-sensitive sniffer, something like an artificial flying bug? You could turn thousands of those suckers loose and when one sniffed him out, a homing signal would go off.
Yes that would be good, but all we really need is one rat.