Home: Animals: Reptiles: : Nile Crocodile

Bio Facts
Common Name: Nile Crocodile Nile Crocodile
Scientific Name: Crocodylus niloticus
Family: Crocodylidae
Order: Crocodylia
Class: Reptilia
Range:

Mostly found in south and central Africa and Madagascar, rare in North Africa
Habitat: Rivers, freshwater marshes, estuaries and mangrove swamps
Description: As with all crocodiles, the lower 4th tooth is exposed when the mouth is closed.  Eyes, ears, nose are on top of the head and can close when submerged.  The snout of the crocodile is triangular.  Skin is heavily armored with a protective covering of bony plates called osteoderms that lie within the skin.  The Nile crocodile can reach lengths of 16 feet and may easily exceed 1000 pounds.  The tail makes up about half the length of the animal.  Juvenile crocodiles are dark olive to brown with darker cross-bands on the tail and body.  Adults are uniformly dark with cross-bands on the tail.
Life Expectancy:

Approximately 45-50 years but can exceed this in captivity.  Some large Nile crocodiles (18+ feet) are reputed to be 100 years or older.
Sexual Maturity:

Females reach their sexual maturity around 10 years of age (6 ½ feet).  Males reach maturity around 10 years of age (10 feet).
Diet: In the wild, they eat a variety of vertebrates.  In the Zoo, they are fed rats and chickens.  As with the alligators, they are fasted three to four months per year during the winter.
Status: USF&WS – Threatened; CITES I & II
Behaviors:

Cooperative hunting and feeding has been observed.  When fish are migrating, Nile crocodiles may form a semi-circle across the river and herd the fish.

Although the juveniles are generally restricted to eating small aquatic invertebrates and insects, they soon move onto larger vertebrates like fish and reptiles.  Adults take in a wide range of large vertebrates including antelope, zebra, hippo, porcupines, pangolins, wildebeest and large cats.  Up to 70% of the adult diet consists of fish.  Nile crocodiles have a reputation as being man-eaters.  A number of deaths and disappearances are attributed to them each year.

They do not chew their food.  They swallow mouth-size pieces.  When a larger animal is captured, Nile crocodiles shake their heads violently from side to side or spin rapidly to break off chunks of meat to swallow.  They often scavenge from carcasses, together with a number of other animals, seeming to tolerate each other’s presence.

Breeding occurs in shallow water.  Females build nests in November and December on sandy shorelines, dry streambeds, or riverbanks.  A clutch of 50 to 80 eggs is laid.  Incubation usually takes 70 days.

Adaptations:

Unlike other modern reptiles, crocodilians have efficient four-chambered hearts similar to birds and mammals. The epiglottis blocks water enabling them to capture prey under water as well as on land. Their clawed feet help them climb.  Nile crocodiles can even jump.  Eyes have vertical pupils that open wide in low light making them formidable nocturnal hunters.

The Nile crocodile’s teeth interlock when the mouth is closed.  Jaws are hinged at the bottom.  Their teeth are conical and made for grabbing and holding, not for cutting.  These teeth are replaced should they become worn or damaged.

he crocodile will align itself with the sun to direct more light on the rises of the osteoderms.  Blood is shunted into the osteoderms where it is warmed, much in the same way as a solar panel, and then circulated through the crocodile’s body.

Special Interest:

The Nile crocodile has a rather well known relationship with several species of birds (e.g. spur-wing plover), which are reputed to pick pieces of meat from between the teeth of the crocodiles as they gape.  The birds gain a meal; the crocodiles have their teeth cleaned of scraps they could not eat themselves.  Whether such a mutual relationship actually exists is hard to determine from literature and anecdotal reports.

It has been observed that social status may influence an individual’s feeding success.  Less dominant animals tend to eat less in situations where they come into frequent social contact with other more dominant individuals. 

everal prey animals have been found wedged under submerged branches and stones, leading to reports that crocodiles store unwanted prey until a later date. Some claim that it is necessary for the prey to decompose before the crocodiles are able to tear portions of flesh off, but this is unlikely to be true. The flesh may become softer if the prey remains in water after death, but crocodiles will certainly avoid rotting meat.

Folklore: The phrase 'crocodile tears' is one that has permeated many languages.  Its origin stems from a traditional Indian belief. Having killed the prey, and having proceeded to eat the body, the crocodile was thought to hang over the victim's head and shed tears before finishing the meal. It was also thought that to attract victims the crocodile would utter a curious sound similar to a human moan. When the prey came to investigate the apparent distress signal the crocodile would leap.
Conservation:

Nile crocodiles are ecologically important as predators. They keep barbel catfish, which are predators themselves, in check. Barbel catfish eat other fishes that are food for more than 40 species of birds. If birds leave an area because there are no edible fish, the amount of bird droppings, which provides nutrients for the fish, declines, and the food chain is disrupted. Unfortunately, the Nile crocodiles' population suffers from pollution, hunting, and entanglement in gill nets.
Jacksonville Zoo History:

According to records, the first Nile crocodile arrived here in October 1972.  This species has been consistently on exhibit since April 1980.  It has successfully bred here.