Tropism
It is a biological phenomenon, indicating growth or turning movement of a biological organism. This is usually a plant in response to the environmental stimulus. This response is dependent on the direction of the stimulus. The stimulus must be perceived first, followed by movement towards or away to the stimulus. There are various types of tropism which are chemotropism, exotropism, geotropism and electrotropism.
I can’t see the image but I would guess animals such as deer or horse or elephants or any large animal have the ability to run over the rocks and turn them to smaller sediments
Would it be its beak? It's hard and protective like scales