Crocodylus johnsoni Krefft, 1873

Species Nomenclature

The freshwater crocodile (Crocodylus johnsoni Krefft, 1873) is a relatively small crocodilian species.

Male Length

Dominant males typically reach a total length of 2.3–3.0 m (7.5–9.8 ft), though 4 metre long specimens have been reported, with a small number of confirmed 4-metre (13-foot) individuals recorded in areas like Lake Argyle and Katherine Gorge.

Female Length

Females reach a maximum total length of 2.1 m (6.9 ft).

Weight

Males commonly weigh around 70 kg (150 lb), while large males can weigh 100 kg (220 lb) or more; females typically weigh around 40 kg (88 lb).

Snout and Dentition

This species is shy, and has a more slender snout and slightly smaller teeth than the dangerous saltwater crocodile.

Body Coloration

Its body is light brown with darker bands across the body and tail, and these bands are usually broken up near the neck.

Head Markings

Some individuals have clear bands or speckling on their snout.

Dorsal Scales

Its body scales are relatively large, with wide, closely connected armored plates on the back.

Flank and Leg Scales

The flanks and outer sides of the legs are covered in rounded, pebbly scales.

Native Range

Freshwater crocodiles are native to Western Australia, Queensland, and the Northern Territory of Australia.

Core Habitat Types

Their main habitats are freshwater wetlands, billabongs, rivers, and creeks.

Saltwater Crocodile Exclusion Habitats

This species can live in areas that saltwater crocodiles cannot occupy, including regions above the escarpment in Kakadu National Park, and very arid, rocky habitats such as Katherine Gorge, where they are common and relatively safe from saltwater crocodiles during the dry season.

Sympatric Habitat with Saltwater Crocodiles

Even so, they are also regularly found in low-lying billabongs, living alongside saltwater crocodiles near the tidal reaches of rivers.

2013 Birdsville Sighting

In May 2013, a freshwater crocodile was sighted in a river near the desert town of Birdsville, hundreds of kilometers south of the species' normal range.

Birdsville Sighting Possible Causes

A local ranger suggested that multi-year flooding may have washed the animal south, or it may have been dumped there as a juvenile.

Ross River Population

A population of freshwater crocodiles has been repeatedly sighted for decades in the Ross River that runs through Townsville, and the leading theory is that frequent heavy flooding in the area washed multiple individuals into the Ross River Catchment.

Nesting Timing

Freshwater crocodiles lay their eggs in nests dug as holes during the Australian dry season, usually in August.

Hatching Timing

The eggs hatch at the start of the wet season, which falls in November or December.

Nest Incubation Defense

Adult crocodiles do not defend their nests while the eggs incubate.

Pre-Hatching Vocalization

Between one and five days before hatching, developing young begin calling from inside their eggs.

Hatching Trigger Function

This calling triggers and synchronizes hatching among sibling eggs, and stimulates adult crocodiles to open the nest.

Nest Opening Parentage

It is unknown whether the adult that opens the nest is always the female that laid the eggs.

Hatchling Transport

When the young emerge from the nest, the adult carries them to the water one by one, holding them in the tip of its mouth.

Hatching Assistance

Adults may also help young break through their eggshells by chewing or manipulating the eggs in their mouth.