more browns than bronzes. Half the dragon population is female, with green dragons being roughly fifty percent of the population and golds being one percent or slightly less. Riding a larger color of dragon confers higher social status in Pern's extremely hierarchical society, color rankings following the dragons' own strict instinctual hierarchical organization based on fire-lizard structures. Perhaps as a result of this, it is commonly believed that the larger colors are more intelligent, although recent novels imply that this may not be true. The Pernese believe that chewing firestone makes female dragons sterile; they therefore refuse to allow queens to use it. Greens, on the other hand, are so common that if they produced offspring it would quickly lead to overpopulation. They always chew firestone, and because of their numbers and agility they are vital to any Thread-fighting force. However, Dragonsdawn suggests that Kitti Ping—possibly motivated by old-fashioned ideas about gender roles—deliberately engineered greens to be infertile and gold dragons to be incapable of producing flame in order to protect the gold dragons, the only reproductively fertile females, from the dangers of Thread fighting. Mating and reproduction Mating Both gold and green dragons experience a periodic mating urge. During a Pass a gold dragon will rise roughly once per Turn, and more often at the beginning of a Pass, yet less often towards the end of a Pass. During an Interval a gold dragon may rise to mate only once every four or five Turns. Greens will rise to mate three or four times a Turn, whether this increases or decreases depending on whether or not it is a Pass is unknown. Greens will mate with any male, usually blues or browns. As they are smaller and have less stamina, a green mating flight is much shorter than a gold one. When a female comes into estrus, interested males compete to catch her in a mating flight. Usually, the female chooses the male who impresses her the most with his skill in the flight, although inexperienced females may be caught before making their choice. The pair actually mate in midair; thus, the higher they get during the flight, the longer their mating can last. The Pernese commonly believe that longer matings result in larger clutches. For this reason, queen riders are strongly encouraged to restrain their dragons from eating heavily just before a flight, instructing them to drink blood