OK, time's up. Look at the pigs in the bottom left-hand corner. And that photo
was taken and framed that way on purpose, and now you probably can't un-see that each time you look at the photo. So there's the humour, hidden away in full view within the photograph.
Childish? Puerile? Well, it would have been if I'd put those pigs in the centre of the frame and made them obvious. Heeeeh heeee…. look what those pigs are doing! Mhhhuuuuhhhaaaa, etc. But I didn't, it was kept as a subtle joke hidden within the overall artistic composition of the photograph.
Don't worry if you didn't see it, some of the animals in the photo didn't see it either! Now look again and perhaps see the expression on the faces of some of the animals that you now believe might have seen what was going on in their midst. My own favourite is the expression on the face of that rabbit... "Ewwwwffff!" That little penguin seems to be having a good look though.
So there you go. Is it art? Well, it's not going to change the world, any more than that pocket cartoon in the daily paper that made you chuckle slightly; but if we can't have a bit of a laugh at our own preconceptions and pretentions then I think it's time we gave up and called bullsh!t on the whole damned thing.