I think Toddy's right about the stencils as they are too uniformal in size which would be impossible if painted by hand though I do suspect a certain artistic liberty on some of them though i.e.finger smudging......What I can tell you is that the two in the middle, facing us, were the first to be done (on each side of the stencil) the top one was the very first ...(which will give an indication of the perpetrators height, as we always start at the most comfortable position for us)... then the others ( that is the ones with the pointy bits towards the left) working up & moving to the right ( which suggests a right handed person) ........ they were sprayed on with a certain design or concept in mind but with out a mathmatical or artistic bend ( for bend read, talent) then the stencil was turned over & the previosly mentioned nana was sprayed (again at the comfort height) & so on.& so forth..... looks like the stencil was getting pretty tired further up & towards the left which indicates that the 'artist' stood back to see where he was going to put the last ones ones, I think they were all done by the same guy( with a ladder of some kind).....not very clear all that I know !
Why ? can't say, though Toddy's suggestion of some sort of game sounds plausable, could have been done for a photo shoot too or a competion " how many nanas can you spray on a trunk in a given time, but they are too evenly spaced for such a frenzy. It was certainly planned & done for a reason,
I must admit the effect ain't too bad, certainly doesn't clash with the surroundings (esthetically speaking)
thanks for listening
blacktimberwolf.... specialist in post - neolithic tree bark banana paintings.