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Crocodylus johnsoni
Freshwater Crocodile, Johnstone River Crocodile


By Nikoma Boice

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Crocodylia
Family: Crocodylidae
Genus: Crocodylus
Species: Crocodylus johnsoni

Geographic Range

This species of crocodile is found in the Northern Territory of Australia and Queensland, and also in northern and western Australia.

Biogeographic Regions
australian (Native )

Habitat

This species occupies various fresh water areas such as lagoons, rivers, billabongs, and swamps.

Aquatic Biomes
lakes and ponds; rivers and streams

Physical Description

Crocodylus johnsoni can reach a maximum length of three meters. It has a light brown body with darker bands on its body and tail and lighter brown bands on its snout. It has a morphologically distinct narrow snout with approximately 68-72 teeth total consisting of 5 premaxillary teeth, 14-16 maxillary, and 15 mandibular teeth. The body is covered with scales that are generally large and provide wide armor on the back.

Reproduction

The females nest in holes that are exposed on sandbars during the dry season from August through September. Mating occurs three to six weeks before laying. Clutches average in size between 13-20 eggs and hatch in about 65-95 days. Egg laying usually occurs at night. Eggs are faced with predation by monitor lizards and feral pigs. High and low temperatures (33-34C) produce female embryos while intermediate temperatures (32C) produces male embryos. The nests of eggs are left unguarded, but the mothers reappear in late October. At the end of the incubation period, the mothers carry the newly hatched young to the water in their mouths. The mothers then stay close to the young and protect them for a short period of time. In addition to being hole nesters, they are also sometimes called "pulse nesters" because all females in a given population nest within a brief three week period each season. Individuals reach reproductive maturity when they reach 1.5 meters in length.

Lifespan/Longevity

Average lifespan
Status: captivity

20 years
[External Source: AnAge]

Behavior

When hunting, these animals use a sit-and-wait method of grabbing prey with a swift sideways motion of the head.

Food Habits

This creature eats fish, insects, small invertebrates, amphibians, mammals, birds, and other small vertebrates. Large individuals may consume terrestrial prey.

Economic Importance for Humans: Positive

Humans benefit from this species by using it for its meat, eggs, and its leather-producing hide.

Economic Importance for Humans: Negative

Occasional attacks on humans have been reported.

Conservation Status

IUCN Red List of Threatened Species [Link]
Lower Risk - Least Concern
More Information

Long-term aboriginal hunting did not significantly affect the population despite advances made in tanning processes at the end of the 1950s that allowed the skins of this species, instead of those of the preferred saltwater crocodile, to be used as leather. Hunting did cause a decrease in populaton size but protective measures were taken in the early 1960s. In western Australia they were protected by law in 1962, and in 1964 in the Northern Territory. Queensland did not pass its protective laws until 1974. Illegal hunting continues but the main threat is the destruction of habitat. Small scale ranching and farming of these crocodiles exists.

Other Comments

Other common names include: Johnson's/Johnston's (river) crocodile, "Freshie", and fish crocodile. There are no recognized subspecies although darker-colored dwarf specimens have been identified. Also called Crocodylus johnsoni.

For More Information

Find Crocodylus johnsoni information at

Contributors

Nikoma Boice (author), University of Michigan.

References

Grnard, Steve. 1991. Handbook of Alligators and Crocodiles. Florida: Kreger Publishing Company.

Levy, Charles. 1991. Crocodiles and Alligators. London: Quintet Publishing Limited.

Thorbjarnarson, John. 1992. Crocodiles: An Action Plan For Their Conservation. Switzerland, IUCN.

http://www.flmnh.ufl.edu/cnhc/csl.htm

To cite this page: Boice, N. 2000. "Crocodylus johnsoni" (On-line), Animal Diversity Web. Accessed May 21, 2012 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Crocodylus_johnsoni.html

Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

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