Escudo/pumilio sexing

I thought this might be interesting for people who have trouble sexing out pumilio. Personally unless I see eggs and/or witness calling I am never really positive about the sex of pumilio, escudos in particular. Males can be fat, females slender, etc. Sometimes if you catch a male right after he's called you can see the dark patch under the throat but suffice it to say that they can be tricky to sex, for me at least. Most of my juvenile escudo grow up together in grow out tanks, usually 3-4 in a 10 gallon tank. For a while now I have been trying to sex out a pair from about 8 frogs, a couple FR and the rest CB. I have been swapping them between tanks trying to get them to call or clutch to figure out who's who. Most of the tanks I've been swapping them in and out of are between 10 and 20 gallons. With a lot of frogs, as soon as you introduce them into a new enclosure, the males will start calling, particularly if there is a female present. Haven't had that with escudo and I've swapped these 8 at least three different times over the course of a year or more and I've never heard calling and never seen eggs. So I recently vacated a large ~400 gallon enclosure, my largest, and decided to put my smallest frogs in it, the escudos. I took all eight that I have been swapping around having never heard a peep and put them all into the large enclosure and within 5 minutes had a male calling. Still don't know what the other 7 are but at least I was able to get someone to call.