Johnstones crocodile

Crocodylus johnstonii

TAXONOMY

Crocodylus johnsoni Krefft, 1873, Herbert River, Queensland. OTHER COMMON NAMES

English: Freshie, Australian freshwater crocodile; French: Crocodile de Johnstone; German: Australien Krokodi; Spanish: Cocodrilo de Johnstone.

PHYSICAL CHARACTERISTICS

Johnstone's crocodile has a very narrow snout. Adults average 6.5 ft (2 m) in length. Males grow to over 10 ft (3 m); females grow to 6.5 ft (2 m) and average 5 ft (1.5 m). Dark or light brown in color with black bands or spots on the body and tail. The underside is white. The dorsal scales are quite smooth, arranged in six neat rows.

DISTRIBUTION

Tropical regions of northern Australia.

HABITAT

This species inhabits freshwater rivers, streams, and pools, but occasionally estuarine habitats.

BEHAVIOR

Social animals, Johnstone's crocodiles may form dense aggregations during the annual dry season. Large males and females assert territoriality and dominance by chasing and biting the tails

of smaller ones. These crocodiles migrate considerable distances overland in the dry season. Where there is no water they seek refuge under embankments and in piles of leaves and dense vegetation. Johnstone's crocodiles are quite vocal and growl in response to loud noise or a human presence in "their" pond.

FEEDING ECOLOGY AND DIET

Crustaceans, insects, spiders, fish, frogs, lizards, snakes, birds, and mammals. Insects are the most common food item, followed by fish, which are caught by using a "sit-and-wait" strategy. Johnstone's crocodiles are also known to stalk larger prey; large crocodiles catch and eat wallabies and water birds.

REPRODUCTIVE BIOLOGY

These crocodiles court and mate at the beginning of the dry season (around May). Females dig nest holes in sand banks, sometimes communally, and lay an average of 13 eggs. Average incubation time is 74 days. Females rarely guard the nest and only become attentive when the young signal they are ready to hatch and emerge. The female opens the nest and carries the young to the water, sometimes inflicting puncture wounds on the hatchlings with her sharp teeth. The female stays with her crèche of hatchlings for a month or more. Juveniles that survive to maturity are known to return to the same breeding and nesting areas from which they were hatched.

CONSERVATION STATUS

Seriously depleted by the skin trade but recuperating. Threats to the species are habitat destruction and the introduction of the poisonous cane toad (Bufo marinus), which has led to mortality in otherwise healthy populations. Estimated wild population is at least 100,000. This species no longer appears on the IUCN Red List, but it is on Appendix II of CITES.

SIGNIFICANCE TO HUMANS

Johnstone's crocodiles and their eggs remain a traditional source of food for several indigenous groups and as part of their folklore. ♦

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