Nile crocodile characteristics, habitat, feeding, reproduction

3696
David Holt

The Nile crocodile (Crocodylus niloticus) is the second largest reptile in the world. The adult male, who is larger than the female, can weigh up to 750 kilograms and measure between 3.5 and 5 meters.

This species is part of the Crocodylidae family. Regarding its distribution, it is native to southern, central and eastern Africa, where it inhabits bodies of fresh water and, occasionally, in brackish lakes and deltas. However, it is able to live in saline environments, although it rarely does..

Nile crocodile. Source: Muséum national d'histoire naturelle [CC0]

The body of the Nile crocodile has thick skin, which is covered by scales and osteoderms. These structures provide the animal with strong protection against injuries caused in fighting against predators or conspecifics..

Regarding coloration, the adult has a bronze-brown upper part, with black stripes in the posterior region of the body. In contrast to these shades, the belly is yellowish.

Article index

  • 1 Behavior
  • 2 General characteristics
    • 2.1 Size
    • 2.2 Skin
    • 2.3 Body
    • 2.4 Head
    • 2.5 Gastrolites
    • 2.6 Gular valve
  • 3 Danger of extinction
    • 3.1 Threats
    • 3.2 Actions
  • 4 Habitat and distribution
  • 5 Food
    • 5.1 Hunting method
  • 6 Playback
    • 6.1 The eggs
  • 7 References 

Behaviour

The Crocodylus niloticus It can remain motionless for long hours, either sunbathing or submerged in water. However, at that time, he is very attentive to what happens in his environment. The fact that it keeps its mouth open, apart from being essential for thermoregulation, could be associated with a threat signal, directed at other species.

Nile crocodiles are excellent swimmers, being able to swim for up to 30 minutes at a speed of 30 to 35 km / h. They can also be submerged under water for a few minutes.

On land, this reptile normally crawls on its belly, but it also tends to walk with its trunk raised off the ground. The smaller species gallop, although the larger ones can make a rapid and surprising movement at high speed, reaching up to 14 km / h.

General characteristics

Size

The Nile crocodile is considered the second largest reptile in the world, after the saltwater crocodile (Crocodylus porosus).

This species presents sexual dimorphism, where males are up to 30% larger and heavier than females. Thus, it can measure from 3.3 to 5 meters long, with a weight of 150 to 700 kilograms. As for the female, she is around 3.05 meters tall and has a body mass of about 116 kilograms..

Skin

The skin of the Nile crocodile is covered with keratinized scales. In addition, it has an ossified layer, known as osteoderm. The shields that are located on the face of this reptile are mechanoreceptors. These capture changes in water pressure, thus allowing you to track prey, by perceiving their movements.

Regarding the coloration, the young are gray or brown, with dark stripes on the body and on the tail. In contrast to the color of the upper body, the belly is yellowish green.

When the animal is adult, its skin darkens and the crossed bands disappear. Thus, the dorsal region acquires a bronze tone. Stripes and black spots stand out on the back, while the belly is yellow.

As for the flanks, they are yellowish green, with numerous dark patches distributed in oblique stripes.

Experts point out that there are some variations in the coloring patterns of this species. Those that live in fast-moving waters tend to have a lighter hue than those that live in swamps or lakes. This constitutes a camouflage, which allows the animal to go unnoticed in the environment that surrounds it..

Body

The Crocodylus niloticus it has short limbs and a long, powerful tail. Regarding the bone system, the spine has cervical, thoracic, lumbar, sacral and caudal vertebrae.

In the lower back there is a formation similar to the ribs, but with a cartilaginous constitution. These harden the abdominal region, thus protecting the internal organs found in that area..

Head

The reptile has a long snout, where 64 to 68 pointed teeth are found. If these are damaged, they are replaced. In the front area of ​​the upper jaw it has five teeth, while in the rest of the bone structure there are 13 to 14 mouthparts. In relation to the lower jaw, it has between 14 or 15 teeth.

The eyes of the Nile crocodile have a nictitating membrane, whose main function is to prevent desiccation of the eyeball. The tongue is a stratified, squamous, and keratinized muscle. It has a great variety of tactile corpuscles.

Because the animal spends much of its time submerged, its body has various adaptations. Among these are a membrane in the nostrils, which closes when the crocodile is underwater..

In addition, the ears, eyes and nose are located in the upper region of the head. Thus, the reptile can keep the body sunk, while these organs remain out of the water.

Gastrolitos

The Crocodylus niloticus he has gastroliths in his stomach. These are rounded stones that the animal voluntarily swallows. Its function could be associated with the contribution in the chewing of the food that it ingests.

Gastroliths are not present in the offspring, but they do exist when the animal measures between 2 and 3.1 meters. Thus, an adult species that weighs 239 kilograms and measures around 3.84 meters could have up to 5.1 kilograms of these stones in its stomach..

Gular valve

The gular or palatal valve is a kind of flap that is in the posterior region of the mouth. While the animal is submerged, this structure closes access to the esophagus, thus preventing water from entering the lungs.

Anatomically, the ventral and dorsal elements of this valve form an efficient seal, which divides the pharyngeal cavity from the oral cavity, according to its behavioral or nutritional needs. In this way, the folds of both regions are complemented by other smaller roughnesses, located on the edges of the palatal.

Danger of extinction

The populations of the Crocodylus niloticus they are progressively decreasing, due to various factors, such as the fragmentation of the environment where it lives. This situation has caused the IUCN to categorize this species within the group of animals that are at a lower risk of becoming extinct..

Threats

Among the threats that afflict the Nile crocodile is poaching. In this sense, some villagers capture the animal to eat its meat and eggs. Also, various parts of your body, such as fat, blood, and brain, are commonly used in traditional medicine..

On the other hand, this species is a great predator and the fact that its populations are close to urban areas creates fatal confrontations with man..

This generally occurs because the crocodile attacks livestock, when the bovid approaches the lakes to drink water. Because of this, the breeders, to preserve the herd, kill the reptile.

Overfishing and pollution are depleting fish, which are the main prey in their diet. This negatively affects the C. niloticus, since they are forced to migrate from their natural habitat, in search of food.

In relation to the degradation of the environment, the construction of dams in the bodies of water causes the flooding of the resting areas of the Nile crocodile. Also, the inhabitants are destroying the ecosystems, to allocate the lands to agricultural areas and urban planning.

Actions

In a large part of its distribution, the Crocodylus niloticus It is included in Appendix I of CITES. While, in other regions, such as Egypt, Mozambique, Ethiopia and Uganda, among others, this species is on Appendix II of CITES.

Habitat and distribution

The Nile crocodile is distributed in several countries in central, southern and eastern Africa. Currently, it extends from Lake Nasser in Egypt to tributaries of the Nile River in Sudan, the Olifants River (South Africa), the Okavango Delta (Botswana) and the Cunene (Angola).

Thus, this species inhabits Angola, Cameroon, Botswana, Egypt, Burundi, Democratic Republic of the Congo, Eritrea, Gabon, Ethiopia, Kenya and Equatorial Guinea. Also lives in Madagascar, Namibia, Malawi, Rwanda, Mozambique, Somalia, Sudan, South Africa, Swaziland, Uganda, Tanzania, Zimbabwe and Zambia.

In these regions it is found in deserts, swamps, lakes, rivers, coastal estuaries, and even underground streams in caves. Generally prefers bodies of fresh water, but could extend to brackish waters and even those highly saline, which present fresh water seepage.

Habitat use differs between juveniles, sub-adults, and adults. In this sense, the juveniles disperse when they are around 1.2 meters long. During the winter, the pregnant female locates rest and reproduction areas near the nest. Also, their home range is less than that of non-pregnant females..

Feeding

The Nile crocodile is a predator that can hunt its prey both in water and on land. Their diet is very broad and varies depending on the size of the reptile. Thus, the young mainly feed on insects, such as crickets, beetles, spiders and dragonflies..

They can also occasionally hunt mollusks, crabs, and amphibians, such as the common African toad and the cane frog. When the Nile crocodile is between 5 and 9 years old, it eats insects, arachnids, fish and amphibians, among which is the Goliath frog (Conraua goliath).

In general, juveniles and sub-adults prefer reptiles, such as turtles, and some small mammals, such as rodents and shrews. In relation to birds, they are also included in the diet of this species, especially pelicans, eagles, waders and aquatic birds..

Adults can capture monkeys, hares, bats, pangolins, gazelles, small primates, lemur, aardvarks (Orycteropus afer) and African manatees (Trichechus senegalensis).

Hunting method

If the prey is in water, the Crocodylus niloticus it is a fast and agile hunter, who uses its mechanoreceptors to locate the animal. However, on land, the reptile uses its limbs, which allow it to gallop to chase its prey..

In both cases, he uses the ambush as a surprising means of attack, a technique that guarantees success in capturing the animal..

Reproduction

Sexual maturity is reached by the Nile crocodile at around 12 and 16 years of age. In the male this occurs when he is around 3.3 meters tall and weighs 155 kilograms. As for the female, she can reproduce when her body is between 2.2 and 3 meters long..

During the mating season, the male attracts females by hitting the water with his snout. Also, at the same time, it emits some loud vocalizations. Also, strong confrontations can occur between males, for the option of joining a female..

When the female accepts the male, the couple emits loud vocalizations. During copulation, the male makes roaring sounds while holding his partner underwater..

The eggs

As for nesting, it occurs one to two months after mating. The time of the egg laying can vary depending on the region that the Nile crocodile inhabits.

In this way, those who live in the extreme north, in Egypt or Somalia, the nesting is between December and February, while those in the southern regions such as Tanzania or Somalia, it occurs from August to December.

The preferred locations for nest building are riverbanks, sandy shores, and stream beds. In the nesting area, the pregnant female digs a hole of up to 50 centimeters and lays between 25 and 80 eggs. These hatch after approximately 90 days.

References

  1. Somma, L.A. (2020). Crocodylus niloticus Laurenti, 1768. Recovered from nas.er.usgs.gov.
  2. F. Putterill, J.T. Soley (2004). General morphology of the oral cavity of the Nile crocodile, Crocodylus niloticus (Laurenti, 1768). II. The tongue. Recovered from pdfs.semanticscholar.org.
  3. Darren Naish (2013). Crocodiles of Africa, crocodiles of the Mediterranean, crocodiles of the Atlantic (crocodiles part VI). Recovered from blogs.scientificamerican.com.
  4. Isberg, S., Combrink, X., Lippai, C., Balaguera-Reina, S.A. (2019). Crocodylus niloticus. The IUCN Red List of Threatened Species 2019. Recovered from iucnredlist.org.
  5. San Diego Zoo Global Library (2019). Nile Crocodiles (Crocodylus niloticus & C. suchus). Recovered from ielc.libguides.com.
  6. Putterill JF, Soley JT. (2006). Morphology of the gular valve of the Nile crocodile, Crocodylus niloticus (Laurenti, 1768). Recovered from ncbi.nlm.nih.gov.
  7. Anne Marie Helmenstine (2019). Nile Crocodile Facts Scientific Name: Crocodylus niloticus. Recovered from thoughtco.com.
  8. Wikipedia (2019). Nile crocodile. Recovered from en.wikipedia.org.

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