buns vary
When Buffy and Bunster free-ranged they left nothing on the lawn - there's a gentle mound of gravel on the concrete area in one corner, and they very tidily went there (I have read than in the wild buns poo at the higher points - can anyone verify that?).
However, when Bunster died and Sausage arrived, large quantities of droppings appeared on the lawn. He'd come from a rescue, and his run was grassy but level, with no obvious hillocks. At first it was only Sausage pooing on the grass. Now we suspect it is Buffy too. But it is only 'processed grass', so who cares?