Comparing scat counts and thermal drones: differences in precision and population estimates

Precise monitoring of wildlife populations is a key part of conservation management, but estimating animal numbers across large landscapes is often difficult. In Australia, this challenge is particularly relevant for kangaroos, where high population densities can place significant grazing pressure on native vegetation and ecosystems. Choosing an appropriate population monitoring method can directly influence management decisions on conservation reserves.

For my Honours project, I worked with Bush Heritage Australia to compare two methods of macropod monitoring; traditional scat counting and thermal drone surveys. While scat counts have long been used as a low-cost, indirect method of estimating abundance, drones are increasingly being adopted in applied ecology for their ability to cover large areas quickly with minimal disturbance to wildlife. The two monitoring methods were employed simultaneously during fieldwork in March and April 2025 on two conservation reserves in central Victoria.

Isabel Overhill undertaking a macropod thermal drone survey

We discovered that population estimates derived from thermal drone surveys were around 70% higher than those from scat counts and were substantially more precise, with much tighter confidence intervals – meaning repeated surveys would be more likely to produce similar results. A difference of this magnitude could influence decisions about grazing management or vegetation recovery targets. However, scat counts were far more cost-effective, roughly half as expensive as a drone-based monitoring program. This cost difference was driven primarily by the processing time associated with thermal imagery. Our findings offer a baseline comparison of the two monitoring methods for estimating macropod populations, highlighting an important trade-off for conservation managers between precision and cost.

While scat counts remain a practical tool, thermal drones offer a powerful way to improve confidence in population estimates at reserve scales. As drone and thermal technologies continue to advance and become more affordable, they are likely to play an increasingly important role in wildlife monitoring and conservation decision-making. Ultimately, selecting the right tool will depend on management objectives, available budgets, and the level of precision required to guide action.