Fig 1.
Lace monitor (Varanus varius, top panel) and yellow-spotted monitor (V. panoptes, bottom panel).
Both species are large apex predators with generalist diets.
Fig 2.
Active searches and motion-triggered cameras were used to estimate the relative abundance of lace monitors (Varanus varius) in 21 populations along the east coast of Australia (shaded symbols) and in 24 populations of yellow-spotted monitors (V. panoptes) in tropical Australia (open symbols).
Sites were allocated into invasion stages based on the number of varanid generations that cane toads had been present. Diamonds–uninvaded; circles–recently invaded (1–12 varanid generations); squares–mid-term invaded (13–29 varanid generations); triangles–long-term invaded (30–80 varanid generations). This map was generated in QGIS 3.12.3.
Fig 3.
Numbers of animals detected per day based on active searches and remote-sensing cameras at 21 sites along the east coast of Australia (left panels) and 24 sites across the tropical transect (right panels). Top panels display the mean (± se) number of the varanid lizards (a) lace monitors (Varanus varius) and (b) yellow-spotted monitors (V. panoptes), middle panels (c, d) represent the mean (± se) number of cane toads (Rhinella marina) recorded, and lower panels (e, f) show the mean (± se) number of small mammals (< 250 g) detected. The invasion categories are based on the number of varanid-generations for which cane toads have been present in the landscape (uninvaded–toads not present; recently invaded–toads present for 1–12 varanid generations; mid-term invaded–toads present for 13–29 varanid generations; long-term invaded–toads present for 30–80 varanid generations). Following a significant main effect of invasion stage, we ran post-hoc estimated marginal means contrasts to test for significant differences between invasion stages. Cases with p < 0.05 are indicated by contrasting letters.
Table 1.
Akaike’s information criterion (AICc) scores were used to rank candidate models testing the effect of invasion stage (uninvaded, recently invaded, mid-term invaded and long-term invaded), mammals (counts), toads (counts), the interaction between mammals and toads, temperature, vegetation, and rainfall on the relative abundance of lace monitors (Varanus varius) and yellow-spotted monitors (Varanus panoptes) at 45 sites in Australia.
Table 2.
GLMM outputs for models testing relative abundance of cane toads (Rhinella marina) as a function of time since cane toads invaded.
Table 3.
GLMM outputs for models testing relative abundance of small mammals (mass < 250 g) as a function of time since cane toads invaded.