Compared with a grazing kangaroo, Petrogale has shortened, wider hind feet with granular, spongy pads covering the sole and much less prominent claws. On rock the useful force is friction, and a compliant pad that conforms to irregularities in the surface generates far more of it than a claw designed for soil ever could.
The rest of the body follows the same brief. The tail is long, flexible and cylindrical, used as a counterweight and balancing rudder rather than as a prop for standing, and the limbs are proportioned for bounding and stopping in short distances rather than for covering open ground. Animals routinely leap between boulders and land on surfaces a few centimetres wide.
Colony structure is the conservation problem. Rock-wallabies are tied to specific outcrops, so populations are naturally fragmented and cannot easily recolonise a site after local extinction. Fox predation and competition from feral goats for shelter and forage, rather than the pelt trade that ended long ago, are the pressures that matter now.