Girls are cool
Being cold-blooded, sunset brings an end to most reptiles' activity, but not the leopard gecko. Like most geckos, the leopard gecko is nocturnal and able to get all the heat it needs from the rocks that retain their heat for several hours after the sun has set. In the cool night, a brightly coloured male and a less brightly coloured female inspect each other. The male collects her scent with his tongue and is able to tell that she is female and sexually available. Interested, he wiggles his tail, nibbles her neck and strokes her flanks until copulation begins. With mammals and birds this is the time when the sex of the young is determined, but not so with a number of retiles - including geckos. For them it is temperature that is all-important. If the female chooses to lay her eggs somewhere warm then her young will be males. If she chooses to lay her eggs somewhere a few degrees cooler, then they will be females.