Nile Crocodile

## Description

The Nile crocodile (Crocodylus niloticus) is a large crocodilian that lives in freshwater habitats in Africa. There it is present in 26 countries. The Nile crocodile is one of the most dangerous species of crocodile and is responsible for hundreds of human deaths every year. It is common and is not endangered, despite some regional declines or extirpations.

## Appearance

The Nile crocodile is one of the largest crocodilian species. Females are noticeably smaller than males. Their bodies are streamlined, the tails are long and sturdy, and the hind feet are webbed. Nile crocodiles have long and powerful jaws, which perfectly fit catching and holding the prey. Due to a special valve, found at the back of their throat, these crocodiles can move underwater with an open mouth, and grab and hold prey without ingesting water. Nile crocodiles are grey-olive in color and have yellowish bellies. Young individuals are identified by greenish or dark olive-brown coloration and black-colored cross-banding all over the body and tail. As they grow up, the banding on their bodies becomes fainter.

## Distribution

Nile crocodiles are found across Sub-Saharan Africa. They most frequently occur in the central, eastern, and southern regions of Africa as well as Western Madagascar. Nile crocodiles can live in a broad range of habitat types, including small brackish streams, fast-flowing rivers, swamps, dams, and tidal lakes and estuaries. In East Africa, they are found mostly in rivers, lakes, marshes, and dams, favoring open, broad bodies of water over smaller ones. They are often found in waters adjacent to various open habitats such as savanna or even semi-desert but can also acclimate to well-wooded swamps, extensively wooded riparian zones, waterways of other woodlands, and the perimeter of forests. In Madagascar, the remnant population of Nile crocodiles has adapted to living within caves. Although not a regular sea-going species, the Nile crocodile possesses salt glands like all true crocodiles and may occasionally enter coastal and even marine waters.

## Lifestyle

Nile crocodiles are solitary animals. However, they can occasionally be seen feeding in small groups, consisting of several individuals. They usually use a special technique, enclosing an area of water in order to concentrate fish within it. Then, dominance hierarchies decide, in what order the members of the group will feed. These reptiles are mainly nocturnal. By day, the crocodiles typically sunbathe or cool off in the water if needed. Male crocodiles are highly territorial; they patrol and defend their territories, which often include a part of the shoreline, extending about 50 meters into the water. Nile crocodiles usually dive for a few minutes, before they come to the surface; however, when threatened, they are able to remain submerged for up to 30 minutes. Moreover, when completely inactive, these reptiles are capable of holding their breath for as long as 2 hours. They are exceptionally fast runners, and in general, these crocodiles have very quick reflexes, but, unfortunately, tire quickly.

## Diet

Nile crocodiles are carnivores and scavengers. They feed upon a wide variety of animal species, including insects, amphibians, fish, and land mammals such as giraffes or Cape buffaloes. Newly hatched crocodiles usually start with insects, eventually going over to larger prey. Nile crocodiles also scavenge or steal kills from other predators, such as lions and leopards, and groups of Nile crocodiles may travel hundreds of meters from a waterway to feast on a carcass. They will also readily feed on dead hippopotamuses.

## Reproduction

Nile crocodiles have a polygynous mating system, where one male mates with a number of females. Male crocodiles usually attract receptive females, making a wide variety of noises through bellowing, slapping their snouts in the water, or blowing water of out their noses. Meanwhile, larger males are typically more successful in finding mates. The nesting season in this species occurs in November-December. During this period, a female crocodile digs a nest, which is a hole in a riverbank or sandy river bed. Then, 25-80 eggs are laid and incubated for 80 - 90 days. When the hatching time approaches, the female opens the nest, carrying her offspring to the water. After a while, the young join a crèche of juveniles, which is looked after by females. The hatchlings can remain in this crèche for the first 2 years of their lives. Nile crocodiles become reproductively mature at 12-16 years old.

## Population

### Population threats

The primary threats to this species have to do with humans. Thus, the reptile attracts hunters for its skin, which is used in the production of high-quality leather. On the other hand, being large and dangerous predators, the Nile crocodiles face aggression from humans, who destruct their nests and frequently kill the crocodiles. Attempting to remove caught fish from fishing nets, these animals occasionally damage the nets, which leads to conflict between the crocodiles and fishermen. In Greater St Lucia Wetland Park in South Africa, the animals are threatened by the invasion of exotic plants that shade and supplant their nesting sites, cooling their eggs, which can potentially bring an all-female population.

### Population number

Classified as Least Concern (LC) on the IUCN Red List, this reptile is currently not endangered. The overall estimated population of the Nile crocodile varies from 250,000 to 500,000 individuals.

## Fun Facts

Sex of the future offspring greatly depends on the temperature of incubation: when the temperature is less than 31 degrees Celsius, the hatchlings are likely to be females, while temperatures over 31-34 degrees Celsius usually yield males. As the hatching time comes, the young give out a “peeping” call; the female hears the call and unearths the eggs, helping the hatchlings come out.

Nile crocodiles, together with their eggs, have been found in Egyptian tombs.

The ectothermic metabolism of these crocodiles is highly beneficial for them. A large individual, weighing over 900 kg (2000 lb.), is capable of going for long periods of time without eating.

When hatchlings are threatened, the mother picks them up, taking them into her gular (throat) pouch, where they find protection.

Usually, both parents help the hatchlings come out of the eggs; they roll the eggs between their tongue and palate, cracking the eggs shell to make the escape easier for their offspring.