What is happening to my apple tree?

[Kosenrufugirl]

Hi there, any advice would be much appreciated.

I have planted an apple tree on the common. Not a rabbit in sight and only well behaved and supervised dogs around.

I have just noticed some damage. I am at a loss what the cause might be.

The tree is on the dwarfing stock. However, I have a lot of trees on the dwarfing stock and this is the only one affected.

All opinion and advice would be gratefully received

Squirrels or deer?

I would out some protection on it

Thank you. I put a plastic bottle around it (cut in half and secured with some tape). It does look like damage done by animal teeth. So you don't think it's some sort of a disease?