20. Animal Senses
American Crocodile
Crocodiles! They look like they walked straight out of the Jurassic Period some 200 million years ago. The American crocodile is scary-looking and big, averaging 12-14 feet (a few up to 20 feet) and an average weight of around 1000 pounds. They aren’t picky eaters, consuming what is in the water, feeding in the water and on the banks. Fortunately for us, they are quite shy of humans and usually retreat. I said usually, they have taken people, and big ones have been known to take cows. They live 50-70 years in the wild. The primary way to tell crocodiles from alligators is that they have a longer snout, and their body color is a lighter gray.
An unexpected aspect of crocodiles is the females’ maternal instincts. She digs a nest along the river and lays 30-60 three-inch eggs. She then buries the nest, and this is the tricky part. The nest’s temperature needs to be close to 89 degrees to balance male and female hatchlings. If the temperature is higher, most will be males; if lower, mostly females; if 82 degrees or lower, the eggs won’t hatch. The nest must be made precisely and oriented correctly with the sun. The female ferociously defends the nest. The eggs incubate for around 75 days and begin hatching. The hatchlings start calling and the female diggs the nest out. If some eggs don’t open, she takes them in her mouth and gently breaks them. She then puts them all in her mouth and takes them to the river. Within a couple of days, the hatchlings are hunting. The mother usually stays around, attentive to their needs and giving them rides on her back. At five weeks, the hatchlings disperse, and predators eat most.
Crocodile senses are extraordinary. Their sense of sight is acute. Crocodile eyes have vertical pupils, as do many night-hunting animals. The vertical pupils can regulate the light coming into the eye better than a round pupil. This is helpful in the daylight, where too much light could damage the eye. They have another common nocturnal vision quality. They have a reflective coating behind the retina that captures light that may have missed the retina and sends it back, doubling their night vision. This is also what gives the scary glow to the eyes at night. They also have a third eyelid that protects the eye underwater. Their hearing is well developed, with slits near the eyes and flaps that cover them underwater. They can regenerate hair cells in the ear and have no hearing loss with age. Scientists are studying this. Crocodiles have an extensive range of sound frequencies, from ultrasonic to subsonic, and may also vocalize in that range. Smell is a strong sense for them with olfactory receptors in their long nasal passages. Above water, they can smell some prey for miles. Not much is known of their sense of taste, but they do fondle each other with their mouths during mating.
Crocodiles’ super sense is their sense of touch, or more precisely, their ISO, integumentary sense organs. These bump/pits are attached to nerve endings found dappling the body and clustered around the mouth. As embryos, these develop before the scales. These organs are actually multisenses. ISOs are pressure sensors, mechanosensors, vibration sensors, temperature sensors, and chemical sensors; one of the greatest arrays in the animal kingdom. Their sensitivity is so great that they can detect one drop of water entering a pool. Underwater hunting can be done with these sense organs alone.
The extreme fear of reptiles is called herpetophobia. While most people don’t have a full-blown phobia of reptiles, many have a strong dislike. Mythology, folklore, and religion have all predisposed us to fear them. Fear, disgust, and contempt are common among people, regardless of age, gender, or profession. But as shown above, American crocodiles are fascinating creatures, but giving them plenty of personal space is good.
Mark W McGinnis 