I'd also like to add that the only time these frogs are really easy to find in the wild is during breeding season when they are all out looking for pools to mate in. The rest of the time, they are buried to their eyes in soil. I imagine that to get any decent sample size, scientists would have to collect their specimens during mating season (otherwise you could dig up acres of rainforest looking for the right species and age-group of frog!). I seriously doubt that breeding season diets (when they are in a different environment, at the same time as many other amphibian species seeking out rainy-season mating pools) is the same as their diet the rest of the time.

Just a warning; a baby may not take nightcrawlers at first. It took a while for mine to go for anything that wasn't actually crawling. It may take a few feedings of crickets before you can get yours to eat nightcrawlers regularly (some frogs love them immediately though, so maybe you won't have to worry).

Also, if you want to use fish as a treat (once or twice a month max) most petstores sell frozen silversides. These are a safe species to feed, and the frozen ones don't have a parasite risk. I prefer these as treats to mice, as they are slightly less fatty but my frog still seems to appreciate the 'real meat'.