My dog has been trained to defecate on command ...admittedly when we go out for her morning 'emptying' walk! She chooses her spot..off the track (has to be exactly the right place). I always have poo bags to remove the dog logs from ground, take to bin.
The cat has several favourite spots in our jungle-like garden...none in a flower bed!
(I have seen a cat training method which enables them to use the human toilet! Seems to work....)