Hi Bella Otterhound here….what a question to ask a nice girl like me !!
I have done a bit of research & the technical explanation is this –
Unfortunately, the desire to roll in animal muck, urine, rotting carcasses and other strong smelling disgusting things is a natural instinct that stems back to your dog's ancestry. In the wild, dogs did this to mask their own scent so that they could creep up on their prey more easily.
In doing so they smell like their prey which makes hunting & survival easier.
My own theory is similar but a bit more fun – it is because we actually like it. A dogs primary sense is smell whereas in humans it is vision. We like rolling in poo the same as you like looking at art. To get a good covering of fox poo is a bit like winning the doggie lottery.
Rolling in poo and other strong smelling substances is such a deeply ingrained dog habit that it is extremely difficult to stop. The neck is usually the most popular although the well practiced can reach all parts of their back.
Sorry humans, fox poo is here to stay. Keep the shampoo in easy reach. Remember we do a very good aloe vera range.