This article details legacy fieldwork (1975–1988) by the late John Toop to document the dynamics of the Mount Etna (central Queensland) Ghost Bat Macroderma gigas colony. John Toop’s work on the Mt Etna Ghost Bats provided empirical data for the first time on the ecological requirements of this species and raised awareness of what has been confirmed to be the significant downward trend in the local population. The findings from this original work included confirmation of the crucial connection between cave architecture, retention of heat and humidity and the survival of young Ghost Bats; description of the seasonal movements of this population, largely as dictated by the above; description of the common suite of prey; discovery that the average body mass of adults from the Mt Etna colony is greater than the recognised weight range for the species; discovery that the average gestation period in the Mt Etna colony was longer than recognised for the species; indications that breeding pairs were barely achieving replacement levels; and crucially, the first reliable indications that the local population of Ghost Bats was declining. Thanks to the pioneering work done during this study, current conservation management aims to minimise disturbance of the bat colony at critical stages of its life cycle and to preserve foraging habitats adjacent to the limestone outcrops.