Hey, not sure if my info is 100%, so you might want to try the Aquatic Inverts, Reptiles, and Amphibians section, but I'm pretty sure that the males have some sort of glands behind their front legs. Dunno if I'm right though. . . .
Good luck with it!
It'd probably be best in a species tank (maybe 15-30 gallons) with 5-10 frogs in it, that's probably where'd you'd have the best opportunity.
Hope my info helps!
Cheers,
GobyMaster