As teeth wear in eastern and western grey kangaroos, the pattern of enamel ridges changes. This affects the amount of available cutting edges and consequently the masticatory efficiency. These kangaroos also have molar progression. There is evidence for the independence of rates of tooth wear and molar progression, and variation is found in the maximum amount of wear attained by teeth both within and between populations. This variation has the potential to affect diet selection, digestion and population parameters.