You could offer some to the water dragon and see of he eats it. If he does you have your answer. Does he watch you eat, he might need to see you eat it to know it's food , or if he's a greedy gutz, he might taste it and eat it right away.
My little mate Lizzy the Eastern Water Skink (our house-lizard) has eaten little bits of ham, cooked turkey, lamb, beef (little bits off my steak), chicken (diced), and even little offerings of cooked fish. But I think Lizzy is very opportunistic and will eat most anything he see us eating if we leave a little bit of it for him on his food treat lid on the kitchen floor.
Lizzy smells new stuff before he takes it off the dish to eat it, but Lizzy watched us like a hawk when he saw us in the kitchen or eating breakfast or lunch or dinner (in summer).
