Yeah Fuscus i was thinking exactly the same thing, a toad cam is needed here.Whatever it is warrants a closer look that's for sure.It's definitely not ants, they'd have eaten pretty well everything down to the bones.I still remember doing a biology experiment with toads and we chucked em on ants nests,they cleaned em up and i stained the skeleton blue 8)
This is not just a toad here and there, he's found quite a few.