D.tinctorious sexing

I have recently acquired my first ever dart frogs, a pair of D.tinctorious 'cobalt'.
I could really do with some help on how to sex them, the only noticeable difference is that one is about double the size of the other!!!

Here is a picture of the bigger one.

Hi there,

You have a few methods that indicate the sex of D.tinctorius which include;

● Toe Pads - Males will have a much larger and more heart shape to their toe pads compard to females who have small ones in comparison.
● The Width of the specimen can sometimes be an indicator of sex, Females will appear "fatter" than males due to carring eggs however I see really huge D.tincs nowadays, in fact most Dendrobatidae and Mantella seem to be way over fed.
● Arched Back - Females will have this really dramatic hunch or arch in their backs, males dont have this pronounced.

These are the methods I personally use however they aren't always an indicator but to be honest they work alot more than not lol

You said the only noticable difference is one is double the size well firstly I would ask, are they the same age? Size is not a fair indicator IF they aren't the same age and grown up together. The one Pictured to me (cant see it very well its not the photo though I cant zoom in) looks like a Male if you go by its Arch in its back.