At the beginning of *The Orville*, we are told that Moclans are an entirely male species. However, the third episode reveals that, in rare cases, Moclans are born female and that corrective surgery is performed to make them physically male. This becomes an important plot point over the course of the series as more and more female Moclans are discovered who live to adulthood and desire to be recognized.

[Wikipedia states](https://en.wikipedia.org/wiki/Female#Defining_characteristics) that the defining biological characteristics of a female is the production of ova (i.e. an egg), but that doesn't apply for Moclans since Bortus lays an egg in the second episode despite being classified as a male and having another male as a mate.

So what is the physical difference between a male Moclan and female Moclan?