[The Half-Hobbit]

It may also be that females are born as often as males, but do not often live to see adulthood. Hmmmm...a sex linked gene that would be carried by the males and expressed in females (like backwards hemophilia) might eplain it. Or maybe they are like alligators, and external factors decide the sex of the offspring...if their living space had the conditions that favored male births that would explain why they (females) aren't born as often.