page_title: Nile crocodile
section_title: Reproduction
hierarchical_section_title: Nile crocodile / Reproduction
caption_attribution_description: Juvenile Nile Crocodiles
context_page_description: The Nile crocodile is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. Due to its widespread occurrence and stable population trend, it has been listed as Least Concern on the IUCN Red List since 1996. It is widely distributed throughout sub-Saharan Africa, occurring mostly in the central, eastern, and southern regions of the continent, and lives in different types of aquatic environments such as lakes, rivers, swamps, and marshlands. Although capable of living in saline environments, this species is rarely found in saltwater, but occasionally inhabits deltas and brackish lakes. The range of this species once stretched northward throughout the Nile, as far north as the Nile delta. On average, the adult male Nile crocodile is between 3.5 and 5 m in length and weighs 225 to 750 kg.
  However, specimens exceeding 6.1 m in length and weighing up to 1,089 kg have been recorded. It is the largest freshwater predator in Africa, and may be considered the second-largest extant reptile in the world, after the saltwater crocodile. Sexual dimorphism is prevalent, and females are usually about 30% smaller than males.
context_section_description: On average, sexual maturity is obtained from 12 to 16 years of age. For males, the onset of sexual maturity occurs when they are about 3.3 m (10 ft 10 in) long and mass of 155 kg (342 lb), being fairly consistent. On the other hand, that for females is rather more variable, and may be indicative of the health of a regional population based on size at sexual maturity. On average, according to Cott (1961), female sexual maturity occurs when they reach 2.2 to 3 m (7 ft 3 in to 9 ft 10 in) in length. Similarly, a wide range of studies from southern Africa found that the average length for females at the onset of sexual maturity was 2.33 m (7 ft 8 in). However, stunted sexual maturity appears to occur in populations at opposite extremes, both where crocodiles are thought to be overpopulated and where they are overly reduced to heavy hunting, sometimes with females laying eggs when they measure as small as 1.5 m (4 ft 11 in) although it is questionable whether such clutches would bear healthy hatchlings.
  According to Bourquin (2008), the average breeding female in southern Africa is between 3 and 3.6 m (9 ft 10 in and 11 ft 10 in). Earlier studies support that breeding is often inconsistent in females less than 3 m (9 ft 10 in) and clutch size is smaller, a female at 2.75 m (9 ft 0 in) reportedly never lays more than 35 eggs, while a female measuring 3.64 m (11 ft 11 in) can expect a clutch of up to 95 eggs. In "stunted" newly mature females from Lake Turkana measuring 1.83 m (6 ft 0 in), the average clutch size was only 15. Graham and Beard (1968) hypothesized that, while females do continue to grow as do males throughout life, that past a certain age and size that females much over 3.2 m (10 ft 6 in) in length in Lake Turkana no longer breed (supported by the physiology of the females examined here); however, subsequent studies in Botswana and South Africa have found evidence of nesting females at least 4.1 m (13 ft 5 in) in length. In the Olifants River in South Africa, rainfall influenced the size of nesting females as only larger females (greater than 3 m (9 ft 10 in)) nested during the driest years. Breeding females along the Olifants were overall larger than those in Zimbabwe. Most females nest only every two to three years while mature males may breed every year.
  During the mating season, males attract females by bellowing, slapping their snouts in the water, blowing water out of their noses, and making a variety of other noises. Among the larger males of a population, territorial clashes can lead to physical fighting between males especially if they are near the same size. Such clashes can be brutal affairs and can end in mortality but typically end with victor and loser still alive, the latter withdrawing into deep waters. Once a female has been attracted, the pair warble and rub the undersides of their jaws together. Compared to the tender behaviour of the female accepting the male, copulation is rather rough (even described as "rape"-like by Graham & Beard (1968)) in which the male often roars and pins the female underwater. Cott noted little detectable discrepancy in the mating habits of Nile crocodiles and American alligators. In some regions, males have reportedly mated with several females, perhaps any female that enters his claimed territory, though in most regions annual monogamy appears to be most common in this species.
  Females lay their eggs about one to two months after mating. The nesting season can fall in nearly every month of the year. In the northern extremes of the distribution (i.e. Somalia or Egypt), the nesting season is December through February while in the southern limits (i.e. South Africa or Tanzania) is in August through December. In crocodiles between these distributions egg-laying is in intermediate months, often focused between April and July. The dates correspond to about a month or two into the dry season within that given region. The benefits of this are presumably that nest flooding risk is considerably reduced at this time and the stage at which hatchlings begin their lives out of t
caption: A grouping of yearling baby Nile crocodiles.
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