page_title: Saltwater crocodile
section_title: Reproduction
hierarchical_section_title: Saltwater crocodile / Behaviour and ecology / Reproduction
caption_attribution_description: Kinabatangan River, Sukau, Sabah, MALAYSIA
context_page_description: The saltwater crocodile is a crocodilian native to saltwater habitats and brackish wetlands from India's east coast across Southeast Asia and the Sundaic region to northern Australia and Micronesia. It has been listed as Least Concern on the IUCN Red List since 1996. It was hunted for its skin throughout its range up to the 1970s, and is threatened by illegal killing and habitat loss. It is regarded as dangerous for people who share the same environment.
  The saltwater crocodile is the largest living reptile and crocodilian known to science. Males grow to a length of up to 6 m, rarely exceeding 6.3 m or a weight of 1,000–1,300 kg. Females are much smaller and rarely surpass 3 m.
  It is also known as the estuarine crocodile, Indo-Pacific crocodile, marine crocodile, sea crocodile or informally as saltie.
  The saltwater crocodile is a large and opportunistic hypercarnivorous apex predator. It ambushes most of its prey and then drowns or swallows it whole.
context_section_description: Males reach sexual maturity around 3.3 m (10 ft 10 in) at around 16 years of age, while females reach sexual maturity at 2.1 m (6 ft 11 in) and 12–14 years of age.
  Saltwater crocodiles mate in the wet season, when water levels are at their highest. In Australia, the male and female engage in courtship in September and October, and the female lays eggs between November and March. It is possible the rising temperatures of the wet season provoke reproductive behaviour in this species. While crocodilians generally nest every year, there have been several recorded cases of female saltwater crocodiles nesting only every other year and also records of a female attempting to produce two broods in a single wet season. The female selects the nesting site, and both parents will defend the nesting territory, which is typically a stretch of shore along tidal rivers or freshwater areas, especially swamps. Nests are often in a surprisingly exposed location, often in mud with little to no vegetation around, and thus limited protection from the sun and wind. The nest is a mound of mud and vegetation, usually measuring 175 cm (5 ft 9 in) long and 53 cm (1 ft 9 in) high, with an entrance averaging 160 cm (5 ft 3 in) in diameter. Some nests in unlikely habitats have occurred, such as rocky rubble or in a damp low-grass field. The female crocodile usually scratches a layer of leaves and other debris around the nest entrance and this covering is reported to produce an "astonishing" amount of warmth for the eggs (coincidentally these nesting habits are similar to those of the birds known as megapodes that nest in upland areas of the same Australasian regions where saltwater crocodiles are found).
  The female typically lays from 40 to 60 eggs, but some clutches have included up to 90. The eggs measure on average 8 by 5 cm (3 by 2 in) and weigh 113 g (4 oz) on average in Australia and 121 g (4 ¹⁄₄ oz) in India. These are relatively small, as the average female saltwater crocodile weighs around five times as much as a freshwater crocodile, but lays eggs that are only about 20% larger in measurement and 40% heavier than those of the smaller species. The average weight of a new hatchling in Australia is reportedly 69.4 g (2 ⁷⁄₁₆ oz). Although the female guards the nest for 80 to 98 days (in extreme high and low cases from 75 to 106 days), the loss of eggs is often high due to flooding and occasionally to predation. As in all crocodilians, the sex of the hatchlings is determined by temperature. At 28–30 degrees all hatchlings will be female, at 30–32 degrees 86% of hatchlings are male, and at 33 or more degrees predominantly female (84%). In Australia, goannas (Varanus giganteus) commonly eat freshwater crocodile eggs (feeding on up to 95% of the clutch if discovered), but are relatively unlikely to eat saltwater crocodile eggs due to the vigilance of the imposing mother, with about 25% of the eggs being lost to goannas (less than half as many Nile crocodile eggs are estimated to be eaten by monitors in Africa). A majority of the loss of eggs of saltwater crocodiles occurs due to flooding of the nest hole.
  As in most crocodilian species, the female saltwater crocodile exhibits a remarkable level of maternal care for a reptile. She excavates the nest in response to "yelping" calls from the hatchlings, and even gently rolls eggs in her mouth to assist hatching. The female will then carry the hatchlings to water in her mouth (as Nile crocodile and American alligator females have been observed doing when their eggs hatch) and remains with the young for several months. Despite her diligence, losses of baby crocodiles are heavy due to various predators and unrelated crocodiles of their own species. Only approximately 1% of the hatchlings will survive to adulthood. By crocodilian standards, saltwater crocodile hatchlings are exceptionally aggressive to one another and will often fight almost immediately after being transported to water by their mother. The young naturally start to disperse after around 8 months, and start to exhibit territorial behaviour at
caption: Seen here is a juvenile crocodile, which grows considerably in length over several years but is easily distinguished by slender build and size.
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