The Crocodile

Aug 30, 2015 Features / Columnists, Interesting Creatures in Guyana

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They are often confused with alligators but there are clear distinctions that make the crocodile clearly different. According to www.livescience.com although it is not recommended in the wild, close inspection would reveal apparent difference in the two creatures.
For instance while the crocodile’s front ends are more pointed and V-shaped, the alligator’s on the other hand has a wider, u-shaped snout.
When its snout is shut the crocodile is said to take on an appearance that suggests that its flashing a toothy grin. This is due to the fact that the fourth tooth on each side of the lower jaw sticks up over the upper lip. But for the alligator, the upper jaw is wider than the lower one, so when it closes its mouth, all of its teeth are hidden.
Added to this crocodiles tend to live in saltwater habitats while alligators hang out in freshwater marshes and lakes.
However, our focus this week is on the crocodile, which seems to have a tendency of turning up every now and then in dwelling allocated for human dwelling.
Just recently one of these creatures was seen wandering through a Crane, West Coast Demerara yard, and it is suspected by some residents that the creature was looking for a suitable place to lay its eggs.
Crocodiles are said to be more closely related to birds and dinosaurs than to most animals classified as reptiles, the three families being included in the group Archosauria (‘ruling reptiles’). Despite their prehistoric look, crocodiles are among the more biologically complex reptiles. Unlike other reptiles, a crocodile has a cerebral cortex and a four-chambered heart. Regarded crocodilians, they have the functional equivalent of a diaphragm by incorporating muscles used for aquatic locomotion into respiration. Salt glands are present in the tongues of crocodiles and they have a pore opening on the surface of the tongue, which is a trait that separates them from alligators. Their function appears to be similar to that of salt glands in marine turtles.
Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may pant like a dog. Four species of freshwater crocodile climb trees to bask in areas lacking a shoreline.
They have acute senses, an evolutionary advantage that makes them successful predators. The eyes, ears and nostrils are located on top of the head, allowing the crocodile to lie low in the water, almost totally submerged and hidden from prey.
Crocodiles are ambush predators, waiting for fish or land animals to come close, then rushing out to attack. Crocodiles mostly eat fish, amphibians, crustaceans, molluscs, birds, reptiles, and mammals, and they occasionally cannibalize smaller crocodiles. What a crocodile eats varies greatly with species, size and age.
Since they have very good night vision, crocodiles are mostly nocturnal hunters. They use the disadvantage of most prey animals’ poor nocturnal vision, to their advantage. The light receptors in crocodilians’ eyes include both cones and numerous rods, so it is assumed all crocodilians can see colours.
They have vertical-slit shaped pupils, similar to domestic cats. One explanation for the evolution of slit pupils is that they exclude light more effectively than a circular pupil, helping to protect their eyes during daylight. On the rear wall of the eye is a tapetum lucidum, which reflects incoming light back onto the retina, thus utilizing the small amount of light available at night to best advantage. In addition to the protection of the upper and lower eyelids, crocodiles have a nictitating membrane that can be drawn over the eye from the inner corner while the lids are open. The eyeball surface is thus protected under the water while a certain degree of vision is still possible.
Crocodilian sense of smell is also very well developed, aiding them to detect prey or animal carcasses that are either on land or in water, from far away. It is possible that crocodiles use olfaction in the egg prior to hatching.
Crocodiles can hear well; their tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles.
Crocodiles reproduce by laying eggs, which are either laid in hole or mound nests, depending on species. A hole nest is usually excavated in sand and a mound nest is usually constructed out of vegetation. Nesting period ranges from a few weeks up to six months.
Measuring crocodile age is unreliable, although several techniques are used to derive a reasonable guess. The most common method is to measure lamellar growth rings in bones and teeth—each ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons.
Bearing this in mind, it can be safely said that all crocodile species have an average lifespan of at least 30–40 years, and in the case of larger species an average of 60–70 years.

 

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