In the outback of South Australia, David Attenborough sits by a shingleback skink, also known as a sleepy lizard. It’s quite a baffling creature because its head and its tail look very similar. But when David brings its hand close to it, it immediately opens its mouth and threatens him with a gape display. When the female catches the eye of a male, the male starts to follow her wherever she goes for up to two months, courting her by gently nudging and licking her. Six months later the female gives birth. It is a long and strenuous business as she does not lay eggs like most lizards but gives birth to two large live young which - together - weigh a third as much as the mother - the equivalent of a woman giving birth to a three-year-old child. Producing such well-developed young is the shingleback's response to the fact that it can get quite cold in south Australia. So, like the Cape chameleon in South Africa, the female acts as a mobile incubator, seeking out the warmest locations in which to bask. Her young are so advanced when they are born that they soon leave home, but when spring returns the same male and female will seek each other out and mate again. In fact, they may remain faithful for as long as twenty years or more. And the bond between them may even endure after death. If one is killed on the roads, the other will stay by its body for days, gently nudging it in apparent grief.