Crocodiles (subfamily Crocodylinae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in the southern oasis , same with Imps and Shalebacks, or in the jungle areas.
Crocodylinae, all of whose members are considered true crocodiles, is classified as a biological subfamily. A broader sense of the term crocodile, Crocodylidae that includes Tomistoma, is not used in this book. The term crocodile here applies to only the species within the subfamily of Crocodylinae. The term is sometimes used even more loosely to include all extant members of the order Crocodilia, which includes the alligators and caimans (family Alligatoridae), the gharial and false gharial (family Gavialidae), and all other living and fossil Crocodylomorpha.
Although they appear similar, crocodiles, alligators and the gharial belong to separate biological families. The gharial, with its narrow snout, is easier to distinguish, while morphological differences are more difficult to spot in crocodiles and alligators. The most obvious external differences are visible in the head, with crocodiles having narrower and longer heads, with a more V-shaped than a U-shaped snout compared to alligators and caimans. Another obvious trait is that the upper and lower jaws of the crocodiles are the same width, and the teeth in the lower jaw fall along the edge or outside the upper jaw when the mouth is closed; therefore, all teeth are visible, unlike an alligator, which possesses in the upper jaw small depressions into which the lower teeth fit. Also, when the crocodile's mouth is closed, the large fourth tooth in the lower jaw fits into a constriction in the upper jaw. For hard-to-distinguish specimens, the protruding tooth is the most reliable feature to define the species' family.[1] Crocodiles have more webbing on the toes of the hind feet and can better tolerate saltwater due to specialized salt glands for filtering out salt, which are present, but non-functioning, in alligators. Another trait that separates crocodiles from other crocodilians is their much higher levels of aggression.[2]
Crocodile size, morphology, behaviour and ecology differ somewhat among species. However, they have many similarities in these areas as well. All crocodiles are semiaquatic and tend to congregate in freshwater habitats such as rivers, lakes, wetlands and sometimes in brackish water and saltwater. They are carnivorous animals, feeding mostly on vertebrates such as fish, reptiles, birds and mammals, and sometimes on invertebrates such as molluscs and crustaceans, depending on species and age. All crocodiles are tropical species that, unlike alligators, are very sensitive to cold.
Despite their fearsome appearance and reptilian pedigree, crocodiles exhibit surprisingly complex social interactions and a remarkable degree of parental investment in their offspring. Crocodiles mate in a similar fashion to other reptiles, but they go to great lengths to construct egg nests. Even after the young hatch, the mothers guard their young for some time.
Crocodiles of both sexes have a slit near the junction of their legs and tail, on their ventral side. Called the vent, this slit leads to their cloaca -- a shared chamber at the end of the reproductive and digestive tracts. The cloaca leads to the oviduct -- roughly equivalent to the uterus and fallopian tubes of mammals -- in females. In males, the cloaca holds their penis, which they keep internally when not in use.
Male crocodiles maintain a territory in which several females may reside. Males will guard their territories from other males through a series of vocalizations and aggressive postures. If such displays do not dissuade a trespassing male, the conflict may become physical. Battling crocodiles thrash, bite and claw their rival, trying to obtain a dominant position. Eventually, the loser will retreat, and the winner will have acquired or successfully defended a bevy of females.
When approaching a female, courting males will emit vocalizations and swim around prospective mates closely, attempting to entice them into breeding.Crocodiles typically mate underwater. The male will grasp the female -- often from the side -- and align their cloacas. The male will evert his penis, and insert it into the female's cloaca. Because the mating activities of crocodiles typically occur in seclusion, and it happens underwater, humans rarely observe the behavior. The mating process typically lasts several minutes, but a given pair may mate several times over the course of one season to ensure fertilization. Eggs are usually laid about four to six weeks after mating.
As the time for egg deposition approaches, female crocodiles construct a large nest of grass, leaves and sticks. The nest serves several purposes: in addition to helping to maintain a thermally stable and appropriately humid environment, the height of the nest reduces the chances that a flood will destroy the eggs. The female will deposit about 50 eggs inside the nest, and cover them before returning to the water. During the 80-odd day long incubation period, the female will attempt to guard the nest from predators. In exceptionally dry years, females may splash water on the nest to prevent egg desiccation.
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