From Science:
It seems that 9-year-old boys aren’t the only male creatures who will join together to torment their female counterparts. When male lizards largely outnumber females, they direct their aggressiveness toward mating partners, population biologists report. Such belligerence, they say, could put lizard populations at risk of extinction.
Lizards were separated into two populations, each with about 70 members. In one population the adults were three-quarter males, and in the other they were three-quarter females. Lizards were allowed to emigrate to another population of the same bias in sex ratio. The mortality and emigration rates of male lizards were unaffected by sex ratio imbalances, the team reports online this week in Proceedings of the National Academy of Sciences. But females were 2 to 3 times more likely to die or be wounded by males when their environment was male-dominated than when it was female-dominated. The team concluded that rather than fighting off male competitors, the too-numerous male lizards forced the females into mating.
More here.