We've had a rescue cat for just over a week now and he had settled in just fine except that he won't poo in his litter tray. He will wee in it, no problem, but poos right next to it but not in it.
Its kept clean, we've changed the type of litter, we've bought a bigger litter tray, he has two trays (although he hasn't really explored where the 2nd one is). Any ideas?