Whose "poop" is it?

Normally I would not write about "poop", but I am in a bit of a dilemma and I need my Ranger from South Africa to assist.  A few weeks ago my husband and I spent relaxing time in Myrtle Beach.  During our absence an unknown creature decided our deck was a good place to leave its 'poop'.  This present was found on an adriondack chair cushion.  All I can tell you it is large enough for a dog or cat (cat maybe) and a lot of it.  My first reaction was to check if all my fish were still in the pond, which they were.  My dear husband took care of removing the remains but put the cushion back on the chair - ugh.  A couple of days later the same present was left in the same place.  All was removed along with the cushion.  It has been three weeks and no 'poop'.  Well so much for that, this morning the 'poop' was back and a lot of it.   Has this animal been storing it up for weeks?  I sure would like to know who or what is leaving these unpleasant presents on our deck!  The reason I need my ranger is when we were on safari in South Africa earlier this year the Rangers could track the animals based on footprints and poop.  I may have to resort to other measures - maybe a trap would work.  What do you think?