A sign written for humans (and dogs)

It’s not often a sign asking dog owners to pick up their pets' poo makes me smile, but this one did.
Most of the signs you see on streets and in public places use a weird sort of passive-aggressive tone.
“It is an offence to let your dog foul this area. Maximum penalty £1,000.”
All very factual but, when you think about it, it's not actually asking people to do anything, is it? Whereas the Canal and River Trust uses a polite, friendly and direct tone.
“Attention dog owners. Please pick up after your dog. Thank you.”
Then it goes on to add what I thought was a nice touch of humour, by addressing the dogs – in their own language.
“Attention dogs. Grr. Bark. Woof.”
Is this more likely to make make inconsiderate dog-owners pick up their pets’ poo? I don't think so, but I don't think it's any less likely either.
And it leaves passers-by with the sense that the Canal and River Trust not only cares about looking after the river banks but also has a sense of humour.
It's a sign written by humans for humans – and dogs.