Could be that your garden is a disputed territorial border and leaving t*rds around is a very prominent way of marking it, instead of burying them like they do normally...
Either that, or there's a really dim cat around, a bit like the Rag-doll I had a couple of years ago that didn't know any better and crapped all over my lawn - I just loved clearing that up before using the lawnmower... >Fortunately Star found someone to take him and he's been re-homed, their problem now ;D ;D ;D (I don't think the new owners came from Chippenham, but they may have moved...
)
