Dendrobates leucomelas, most experienced keepers will grudgingly admit that these frogs are the hardest to accurately sex by their features. Most rely on the males calling to positively identify sex. The females tend to be bigger, but that can be flawed with actual age, feeding and environment.
Males can begin calling as early as 5 or 6 months but females tend to take a year or more to reach sexual maturity.
Try this link
MistKing*::*Resources
Mist real heavy... wait 10 min and turn the speakers up.
My Leucs are so interested in the second call.
Dan