Q.How do you distinguish the sex of a frog?

[!TLDR] Male frogs have vocal sacs and a nuptial pad; females lack both. …

[!ANSWER] The sex of a frog can be distinguished externally by a small number of clear features present only in the male.

Male frogs typically possess a pair of vocal sacs — expandable pouches of skin, usually near the throat, that are inflated with air and used to amplify the male's mating call, a sound used to attract females and to establish territory. During the breeding season, male frogs also develop a nuptial pad, a swollen, roughened patch of skin on the first digit (thumb) of the forelimb, used to grip the female firmly around the body during amplexus, the mating clasp in which the male holds the female while she releases eggs for external fertilisation. …

• Assuming the nuptial pad is present year-round rather than specifically during the breeding season. …