A single gene that regulates testosterone levels in a 'crazy' species of shore bird controls the development of three wildly different types of males, a new study has found. Ruffs have long fascinated scientists for their three types of males, known as morphs, that differ radically from each other in appearance and mating behaviors. A new study has shown that these morphs are produced by a super enzyme (HSD17B2) in the blood of the birds that's able to regulate testosterone levels in males and rapidly break down the hormone normally associated with male dominance and aggression.