Her long hinder legs on the soil, her forelegs on the ball, she drags it towards her as she walks backwards.

The father pushes behind, moving tail first, his head held low.

This is exactly the method of the Scarabaeus beetles, which also work in couples, though for another object.

The Sisyphus beetles harness themselves to provide an inheritance for their larvae; the larger insects are concerned in obtaining the material for a banquet which the two chance-met partners will consume underground.
The couple set off, with no definite goal ahead, across the irregularities of the soil, which cannot be avoided by a leader who hauls backwards.

But even if the Sisyphus saw the obstacles she would not try to evade them: witness her obstinate endeavour to drag her load up the wire gauze of her cage! A hopeless undertaking! Fixing her hinder claws in the meshes of the wire gauze the mother drags her burden towards her; then, enlacing it with her legs, she holds it suspended.