Frogs are opportunistic feeders and when a little frog hops by, it makes a tasty treat. My field guide says motorbike frogs eat smaller frog species . ClimateWatch says they eat mainly arthropods, smaller frogs and juveniles of the same species. 
In mid March I saw four frogs in and around the pond. They were all about the same size, so couldn’t eat each other. I didn’t see any frogs for three weeks then I saw a larger frog (above). I assume this was the first frog to metamorphose and grew fat on an amphibious diet. Oh yeah, and arthropods. A frog tried to eat this wasp (below) but spat it straight back out. The frog survived but may have been stung. The wasp sat on this plant label cleaning itself for quite some time. I guess frog saliva isn’t pleasant.
Motorbike frogs are variable in colour and they can change colour.
Back colour is extremely variable ranging from green with gold mottling (after basking in sunlight) to an almost uniform dark brown (colder conditions) 
I haven’t seen a frog in weeks, but it might just be hiding. I’ll listen out for breeding calls in the coming months. In spring I’ll get some tadpoles from the Tadpole Exchange Program. One day frogs might survive to breed in my garden.
Join the Tadpole Exchange Program to find or share tadpoles with other frog friendly garden enthusiasts. You can join any time, but tadpoles will only be available in the breeding season July-October (depending on the species).
Frog Watch has information about frogs in WA. There are recordings of breeding calls so you can ID frogs you hear in winter in wetlands or your garden.