I build a new vivarium for my poison dart frogs, Phyllobates terribilis orange black foot. I have five of them and didn’t know how many males or females I had. At least three of them were calling so I had at least three males. I was hoping the other two were females so I did a test. I did put one of those two in the new tank just by itself and I played the sound of a calling male several times. It stayed in the tank by itself for about three days but it did not call, so possibly it is a female. Then I put the other possible female with it and played the recording. That same day new one started to call so I have at least four males and maybe a female.
The two were in the tank together for about four days before I added the other three into the vivarium. Now there was some tension! The smaller male had claimed its territorial and wanted to defend it! The bigger male that was put in last had always been the alfa male in their temporary tank. So it also thought it was the boss. The smaller male took the initiative and attached the bigger male. And for a couple of hours they were fighting each other. Needless to say that the bigger male won. Now the five are living together peacefully inn their new home.

Phyllobates terribilis is a poison dart frog from the tropical rain forest in Colombia. It is one of the three dart frogs that are actually used to poison blow darts. Phyllobates terribils is the most poisonous of them, their skin contains enough poison to kill about ten people.
If you like dart frogs, have a look at my frog gallery.