He'll rip the bark off with his teeth, expose the spine and proudly show you the remains. He also likes to make holes in lush lawns. He digs down to eat the grass roots. He chews shoots off bushes, eats ends of branches of precious young trees and buds off flowers. He believes that young and tender growing greens were planted for his taste buds.
Heritage plays a part here.
In the Algarve, in the winter when the sea was too rough for a small boat to go out, the Portuguese Water Dog often herded sheep. He appears to mimic their eating habits. Paradoxically, chewing is not a problem inside. In the house, he can be taught to discriminate quickly. He knows his toys and he knows yours.