The thing about being the Once-ler is that he's a problem solver. It might be ironic that he is, but inventors have to be. So while Garry was certainly more physically capable of dealing with these things, he's not exactly in dire straights.

The skeleton will be easier to cut through. The anatomical model, though - that might be the best bet.

He skids around a 'junction' at the aisles and then pivots on his heel, holding the axe up. He can hear the damn things rattling towards him.

When the anatomical model rounds the corner, he slams the haft of his axe into its cavity.