Help sexing young African bullfrog

[keypsake]

Is it possible to sex a young African bullfrog that is about 2 1/2 -2 3/4 inches? I have read they can be sexed by 4" but mine is still very young. I named it Darwin because, while most would associate the name as male, I think it would also be a very cute female name. I’m quite knowledgeable with reptiles and this is my first amphibian so I am sure there is a lot I can learn! I’ve read about head size, ear size, dorsal stripes, coloration, nuptial pads, and "calling" but my frog is so young I really don’t know at this size. I can say that I have never heard it make any noises as of yet. If it is male, at what age would the calling begin? Some yellowing is just barely starting to show up as of about a week ago but it is still so faint. I am including some pictures to see if anyone might have a clue as to the sex, even just guesses based off appearance are welcome!