REPTILES III

CROCODILIANS

Of all reptiles, the most feared and perhaps least well known are the crocodilians, which includes 22 species of crocodiles, alligators, caimans and gharials. I knew almost nothing about them, except how fearsome they look—especially when you’re sitting in a canoe and see one on the shore (that happened for me in Florida a few years ago). I learned a lot of fascinating things about these creatures of God. They’ve been around about 200 million years. They, like the turtles, were contemporaries of the dinosaurs. As primitive as they look, they are actually the most advanced of all reptiles, and are in fact more closely related to birds than to lizards. They have a more efficient circulatory system; they are more intelligent; and they are way more attentive of their young.

Crocodilians inhabit North America, Central America, South America, China and Southeast Asia, Africa, Australia, India, Pakistan and many Pacific Islands. The Indopacific Crocodile is the largest reptile living. It reaches 23 feet or more, weighing maybe a ton. Even the smallest croc, the dwarf crocodile of Africa, is about 6 feet long.

There’s a lot that’s interesting about the way they care for their young. The female makes a nest, lays

eggs—it varies from species to species, but anywhere from 20 to 80 eggs—and covers them with mud and plant material.

Then, unlike other reptiles, she stays close by. In some species even the male stays around for protection. When the young crocs are ready to hatch they begin to make noise inside the eggs. She will dig into the nest and take the eggs one by one in her mouth. She rolls them gently back and forth until the shell cracks. She then takes the tiny crocs down to the water—she can carry up to 20 at a time in her huge mouth. They will then stay close together for weeks or months. Some even remain in family groups for years.

Despite all this attention and care, mortality rates are as high as 90% in the first year. Many things happen. The female doesn’t sit on the nest like birds so climatic conditions will affect the eggs. If it’s too cool, too wet, or too hot, the eggs will not develop. In many cases, the whole clutch will perish.

Predators hang around even though the female is nearby, because croc eggs are a prime source of food for so many other animals. Many female crocs fast while standing guard but they do need water. Predators wait for her to go get a drink. Lizards, birds, raccoons, foxes and monkeys all raid the nests. If the eggs survive, the hatchlings face a lot of dangers, as the tiny crocs also are food for all kinds of predators—frogs, snakes and turtles, herons, raccoons and other mammals. Interestingly, if the croc survives to adulthood, all these predators will become his prey.

53:45 He is the One who created the two kinds, male and female.

75:39 He made it into male or female.

I think the most interesting thing about crocodilian offspring is that it is truly God who decides the male and female. We know that’s true for everything, but in this case, the sex of the offspring is determined by temperature, not by chromosomes. When the egg is laid, its sex has not been decided. Temperatures during the first half of incubation will determine the sex of each individual. In the American alligator, high temperature creates males, low temperature makes females, but in the crocodile high and low temperatures create females, only intermediate temperature makes males. A small difference in temperature—One or two degrees—makes a marked difference in sex ratio. Within a nest, all may be the same sex or the temperature may vary enough to have all females in the lower layer of eggs and all males above or vice versa. In American alligators, those who build their nests in cool marshes will have all females; those who nest in warm mounds will have all males. Muggers of India nest at different times throughout the season, in fact a single female may nest twice. Those that nest early in the season will produce mostly females; those who nest later when the soil temperature has risen will have mostly males. I think this is fascinating. God is the One who makes each of these creatures into male or female.

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