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Life in Cold Blood

Book by David Attenborough · 3 quotes · Axolotl, Fossilization, Metamorphosis

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AllAxolotlFossilizationMetamorphosisPair BondingShingleback SkinkThyroxine

Life in Cold Blood Quotes

“The chances of any individual animal leaving behind fossilised remains are infinitesimal. First, its dead body has to lie in a place where sediment accumulates. That is most commonly in a lake or sea. Bones lying on the surface of the land are much more likely to be destroyed than preserved. Next, the sediment has to cover the bones before they disappear, preferably even before they are disarticulated. After that, the mud-and the bones within it- has to be compressed and turned into stone by the great, infinitely slow, movements that distort and crumple the earth's crust. That has to happen without the total obliteration of any sign of the bones. And finally, those bones have to be located in the tiny proportion of rocks which happen to be sufficiently close to the surface for them to be discovered by a prospecting palaeontologist. Thus not only have the vast majority of individual animals disappeared without a trace but great numbers of species and families have doubtless existed of which we have no knowledge whatsoever.”

Fossilization
Book:Life in Cold Blood
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“A young male shingleback (skink), in spring, travels quite widely through the semi-desert, seeking a partner. He identifies a female by her chemical scent, her pheromones. He may then start to follow her, trailing behind her with his head close to her tail. The pair may stay together for six to eight weeks. If she is not physiologically ready to receive him, she will keep her body close to the ground. But eventually her mood may change and she will straighten her hind legs so that the rear of her body is lifted above the ground. He then crawls beneath her and twists his body so that their cloacas meet and he is able to insert his sperm. The two then separate and go their own ways. Unlike many lizards, the female retains her fertilised eggs within her until the young are so well developed that they are capable of independent life. This takes a long time. They grow so large that there is only room within her body for a very small number of them — usually no more than three. Then at last, after five months, she gives birth. The young waddle off into the desert and the female resumes her lonely life. But when spring returns, an adult will once again seek out the partner it had during the previous season. Such partnerships may last for as long as two decades. If one individual is killed, perhaps, as happens only too often, crushed beneath the wheels of a car, the survivor may stay beside the body gently licking it. A coldly dispassionate explanation of this is, of course, that the bereaved has formed a liking for its partner’s pheromone and is reluctant to leave its source. Other interpretations, more sentmental and anthropomorphic, might suggest that the survivor is disconsolate — if not grieving.”

Pair BondingShingleback Skink
Book:Life in Cold Blood
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“The axolotl is remarkable because it becomes sexually mature while still retaining the external gills of its larval form. It seems, however, that this is due to nutritional problems. The change from larva to adult is triggered by hormones, including thyroxine produced by the thyroid gland. Conditions in this one lake, both chemical and physical, are such that this gland does not develop properly. But that can be corrected. If an axolotl (Ambystoma mexicanum) is kept in a tank and a little thyroxine added to its water, the animal loses its external gills, climbs out of water and assumes a terrestrial life.”

MetamorphosisAxolotlThyroxine
Book:Life in Cold Blood
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