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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.
Don't Tell Mom
When hatching time nears, the young begin emitting squeaking sounds that scientists suspect may synchronize the hatching of the siblings and alert the mother that hatching is imminent. When the young begin to emerge from their shells, the mother will help dig them out of the nest and transport them to the relative safety of the water. The young will stay near their mothers for several months; when alarmed, the young may vocalize to get their mother’s attention. Upon her approach, they will climb to the safety of her back.
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