Methods

The distribution of toads in the landscape will, like in other wet-dry landscapes, be strongly seasonal. During the dry season, cane toads will persist in seasonal wet refugia (around creeks, gorges, and other sources of permanent water (Letnic; child; Krockenberger etc.). During the wetter months of the year, we expect toads to move out from seasonal refugia and occupy the broader landscape (**Brown, others). To estimate a density of cane toads after the months of highest rainfall, we used the dispersal kernels derived above and applied these to every mapped point of perennial water in the Pilbara. Perennial water points include natural and artificial features such as lakes, reservoirs, settling ponds, swamps, bores, natural springs, water tanks, windmill pumps, and natural drainage points such as waterholes in rocky gorges. This retained 4226 perennial water points across the landscape (Figure 2). Using the Tingley et al. (2013) approach with respect to the number of rainy days, we were able to place a 2-dimensional dispersal kernel on each water point. We then made a regular grid across the entire Pilbara landscape, and summed the kernel densities accruing to each of 155820 grid points from all perennial water points. This produced density values, which we converted to toads per square km. The conversion was done by using a mean number (660) of toads per water feature, as identified in previous studies (Smart et al. 2020; Florance et al. 2011). This method generated a high resolution surface expressing the relative density of adult toads across the full Pilbara landscape by the end of the wet season. Thes animals would be expected to breed, of course, so this is a lower value of the density of toads expected in the landscape. We show this layer as both the continuous density surface, but also as a presence absence surface, where presence is defined as at least one toad per square kilometre. These outputs were each saved as GeoTIFF raster files.