I used this experiment in college. I was studying the territoriality and tenacity of the male D.pumilio. I was actually mimicking the experiment. It was wild to watch the males seek out the source of the "male call" (microphone). They'd call like crazy after the experiment was over trying to out do the recording. That experiment got me hooked on PDFs.
I did this with my Almirante Pumilio about a month ago. It was really cool to watch them look for the other male, when they don't seem to have a problem with each other (provided they're both males :? ). I also found it interesting that the call I played was from a Bastimentos pumilio, which sounds quite different.
There are a lot of calls on http://www.poison-frogs.nl/ I think I got it from there, but wherever I got it, I just downloaded it onto my computer. My leucs are not yet a year old. They are around 8 months old.
Our leucs were our first frogs to start calling. They were already matured and producing viable eggs, but we were really excited about it. So Mike used his cell phone to record the call (he now uses it as his ring for when he gets a text message, pretty cool 8) ). So, we have learned that if you open the lid to the leucs tank and play the call off of his cell phone that the males (we have three) will call back to it as soon as it shuts up! We get a kick out of it. Anyone we have shown that trick to thinks it's pretty cool too! I can't wait to try it on our two little guys when the start to reach maturity to see if it can be a way to sex them.