The squirrel warning in the previous post has reminded me of an episode from the past. One night during my schooldays, my mother found a dead cat outside our house. It had been hit by a car and cast into the gutter. (In Edinburgh, the gutter is the dip between the road and the pavement (sidewalk) where water gathers before draining away. I mention this because I've noticed that this part of the streetscape has different names in different places and you might be imagining something else. Likewise, the actual drain has lots of different names: in Edinburgh it's a siver and in Glasgow it's a stank - some places they just call it a drain, which is a bit disappointing.)
It wasn't bin night in our street, and my mother didn't want a dead cat lying in our dustbin for a couple of days, but it was bin night round the corner in the next street. Ever thoughtful, my mother didn't want to just chuck a dead cat in someone else's dustbin and besides she didn't think it would be very nice for the binmen if they found it, so she got some brown paper and string and made a parcel out of it.
It then occurred to her that someone finding a parcel in a bin might think it contained something interesting (I think I've just realized where I get my over-developed planning bump from), so she wrote clearly on the parcel, 'This is a dead cat.'
Do you think anyone who found that would believe it? Do you think they would they be able to resist opening it?
I imagine something similar happened with the squirrel bin. Someone accidentally encountered the squirrel (and had the living daylights scared out of them, I expect) and considerately thought they would save someone else from the same experience, so they made the sign (they had to go home to do that, and use the pc, the printer and the laminator) and after consideration, decided to use a very simple and direct warning rather than an explanation. It's grammatically correct, apart from the absence of a full stop, which makes it almost unique in the world of signs.
And it arouses the same terrible temptation, just to stick your hand a little bit inside, just to see if there is a squirrel.