What ecological condition on Rottnest Island contributed to the quokka's surprising lack of innate fear toward humans?

The absence of natural land-based predators

The trusting and approachable demeanor displayed by quokkas, particularly those residing on Rottnest Island, is a direct consequence of their geographical isolation and the resulting ecological pressures, or lack thereof. On this island habitat, native land-based predators that typically impose high selection pressure on mainland species are virtually nonexistent. This absence means the evolutionary necessity for perpetual vigilance, alertness, and fear—traits that consume significant energy—was never strongly imposed on the population. Consequently, the quokkas developed a relaxed disposition, as the energy saved from not monitoring surroundings could be diverted to foraging and reproduction, leading to what ecologists term 'island tameness.'