Wombat Poo

Wombats have a habit of doing their business on isolated objects such as rocks or lumps of wood at wombat bottom height.
The deposit is a strange cube shape. 
Apparently this is not because they have square bums but due to the drying of the faeces in the colon and the particular muscular contractions which form the uniform size and corners of the poo.
So there you have it :-)
I have spared you the obvious thumbnail.