8 0 obj Once the eggs hatch, the female may lead the hatchlings to water, or even carry them there in her mouth, as female American alligators have been observed doing. The largest representatives, the Nile crocodile (Crocodylus niloticus) of Africa and the estuarine (or saltwater) crocodile (C. porosus) of Australia, attain lengths of up to 6 metres (20 feet) and weigh over 1,000 kg (about 2,200 pounds).Some fossil forms (such as Deinosuchus and Sarcosuchus) may have been between… Alderton, D. (1998). Poole, Alan F., Rob O. Bierregaard and Mark S. Martell. /Contents [73 0 R 74 0 R 75 0 R] [7][166], Predators of Nile crocodiles eggs have ranged from insects such as the red flour beetle (Tribolium castaneum) to predators as large and formidable as spotted hyenas (Crocuta crocuta). [6], An estimated 10% of eggs will survive to hatch and a mere 1% of young that hatch will successfully reach adulthood. 2��(w�_���jy�T�4 Storrs G. W. (2003). [139][140] Even heavier prey, such as black rhinoceros (Diceros bicornis), have been killed by crocodiles. [82][83], After Nile crocodiles reach 2 m (6 ft 7 in), the significance of most invertebrates in the diet decreases precipitously. The immense bite force, which may be as high as 5,000 lbf (22,000 N) in large adults, ensures that the prey item cannot escape through the grip. [7][141] An additional case of predation on an adult black rhino was reportedly observed in northern Zambia. https://doi.org/10.1017/S0030605311001712 [18][180] In yet another historic crocodile stronghold, the Olifants River, which flows through Kruger National Park, numerous crocodile deaths have been reported. /Filter /FlateDecode The crocodile population in this area is much more sparse, and has not been adequately surveyed. /ColorSpace << [7] After burying the eggs, the female then guards them for the three-month incubation period. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. [7][155] The female may micturate sporadically on the soil to keep it moist, which prevents soil from hardening excessively. /Rotate 0 /Contents [129 0 R 130 0 R 131 0 R] Thiollay, J. M. (1989). Downloaded from https://www.cambridge.org/core. For example, in Lake Turkana, Kenya, 48.4% of crocodiles had empty stomachs. However, compared to the narrow-snouted, streamlined gharial and false gharial, the Nile crocodile is rather more robust and ranks second to the saltwater crocodile in total average body mass among living crocodilians and third among all living reptiles - the massive leatherback turtle (Dermochelys coriacea) has a mean body mass slightly less than that of an average mature male saltwater crocodiles. [18], Females lay their eggs about one to two months after mating. African fish eagles can take crocodile hatchlings up to a few months of age and honey badgers can prey on yearlings. [49][150][152] 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. 13 0 obj >> /Type /Page [7] However, some large crocodiles have been recorded as predators of subadult hippos; anecdotally, the infamous giant crocodile Gustave was reported to have been seen killing adult female hippos. In some areas, the mother crocodiles will only leave the nest if she needs to cool off (thermoregulation) by taking a quick dip or seeking out a patch of shade. /Subtype /XML National laws, and international trade regulations have resulted in a resurgence in many areas, and the species as a whole is no longer wholly threatened with extinction. /Type /Page Based on these findings, it has also been suggested that crocodiles may act as seed dispersers. [18], Herodotus claimed that Nile crocodiles have a symbiotic relationship with certain birds, such as the Egyptian plover (Pluvianus aegyptius), which enter the crocodile's mouth and pick leeches feeding on the crocodile's blood, but no evidence of this interaction actually occurring in any crocodile species has been found, and it is most likely mythical or allegorical fiction. IP address: 104.131.187.206, on 16 Oct 2020 at 05:50:27, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. Preferred nesting locations are sandy shores, dry stream beds, or riverbanks. The two-year-and-younger crocodiles may spend a surprising amount of time on land, as evidenced by the range of terrestrial insects found in their stomachs, and their lifestyle may resemble a semi-aquatic mid-sized lizard more so than the very aquatic lives of older crocodiles. 15 0 obj /Contents [19 0 R 20 0 R 21 0 R 22 0 R 23 0 R 24 0 R 25 0 R 26 0 R 27 0 R 28 0 R] They are agile predators and wait for the opportunity for a prey item to come well within attack range. One of the most striking differences between the American alligator and Nile crocodile is size. [6][15][184][185] While these species are much more aggressive toward people than other living crocodilians (as is statistically supported by estimated numbers of crocodile attacks), Nile crocodiles are not particularly more likely to behave aggressively to humans or regard humans as potential prey than saltwater crocodiles. [11] Most fatal attacks occur when a person is standing a few feet away from water on a non-steep bank, are wading in shallow waters, actively swimming or have limbs dangling over a boat or pier. Occupied with nesting and hatchling care for a total of nearly 6 months (Cott 1975) Communal nesting sites. [10][49] Despite the attentive care of both parents, the nests are often raided by humans and monitor lizards or other animals while she is temporarily absent. Parental care in Crocodilia, with special reference to, Hancock, James A.; Kushlan, James Anthony and Kahl, M. Philip (1992). [3][7] At other times, the female will fiercely attack anything approaching their eggs, sometimes joined by another crocodile which may be the sire of the young. /CropBox [0 0 595 794] In some areas, some number of baboons is taken, such as in Okavango Delta, where chacma baboons (Papio ursinus) are eaten and Uganda, where olive baboons (Papio anubis) are taken. stream /MediaBox [0 0 595 794] WALLACE Abstract Concern has been raised about the lack of population data for the Nile crocodile Crocodylus niloticus in the lower/middle Zambezi valley. [152] Most females nest only every two to three years while mature males may breed every year. Much of the contamination of crocodiles occurs when they consume rancid fish themselves killed by pollutants. As it matures, Nile crocodiles become darker and the cross-bands fade, especially those on the upper-body. [21] Though the Nile crocodile has been hunted since ancient times,[172] the advent of the readily available firearm made it much easier to kill these potentially dangerous reptiles. (2008). The hatchlings are also protected for a period of time, but hunt by themselves and are not fed by the parents. endobj Nile crocodiles normally crawl along on their bellies, but they can also "high walk" with their trunks raised above the ground. /Resources 83 0 R [3][70] Although they can remain practically motionless for hours on end, whether basking or sitting in shallows, Nile crocodiles are said to be constantly aware of their surroundings and aware of the presence of other animals. [42][49] In Lake Kyoga and Lake Kwana, 73.1% of the crocodiles that did not have empty stomachs had fish in their stomachs. [6], Like all crocodiles, they are sexually dimorphic, with the males up to 30% larger than the females, though the difference is considerably less compared to some species, like the saltwater crocodile. >> /Type /Page Predation on amuplariid water snails was especially heavy in Bangweulu Swamp, Lake Mweru Wantipa, and the Kafue Flats, where mollusks representing 89.1, 87, and 84.7% of all prey in these locations, respectively. /F3 149 0 R [8] Young crocodiles feed more actively than their elders according to studies in Uganda and Zambia. << [174] Recovery for the species appears quite gradual and few areas have recovered to bear crocodile populations, i.e. >> In fact, probably much of the food from crocodile stomachs may come from scavenging carrion, and the crocodiles could be viewed as performing a similar function at times as do vultures or hyenas on land. When groups are sharing a kill, they use each other for leverage, biting down hard and then twisting their bodies to tear off large pieces of meat in a "death roll". [3] Specimens shot near Mpondwe on the Semliki River had gastroliths in their stomach despite being shot miles away from any sources for stones, the same applies to the Kafue Flats, Upper Zambesi and Bangweulu Swamp, all of which often had stones inside them despite being nowhere near stony regions. The average estimated size of Nile crocodiles involved in fatal attacks is 3.5 m (11 ft 6 in).

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