Don beat me to it! Sharing anyways:
I’d probably start with a gravel or stucco texture and tweak the color and roughness from there. Increase the bump and/or displacement to get it to pop.
If you have a model of the mound, you could apply this texture directly to it and rely on displacement to get you the intricate details.
Depending on how “covered” in litter you want the poop shape to be, you could apply the same gravel material over your poop texture (never thought I’d type that phrase), and use another texture to control the opacity.
Adjusting the camoflauge texture that controls the opacity of the litter:
Maybe a wombat used this litter box?