Scientific name: Crocodylus johnstoni
Conservation status: Least concern

Appearance

freshwater crocodileThe freshwater crocodile is one of the smaller crocodile species. Males can grow up to 3 metres (9.8 ft) long and females up to 2.1 metres (6.9 ft), however the average size of these crocodiles is about 1.5 metres long. They are slow growing animals and it usually takes a male about thirty years to reach 3 metres long.

The freshwater crocodile is a light brown colour with darker bands on their bodies and tails. The body scales are quite large and the back has wide, closely-knit armoured plates. They have a narrow snout with has 68-72 very sharp teeth. They have strong legs, webbed feet and an incredibly powerful tail. Their eyes have a special clear eyelid which protects the eye while they are underwater.

Lifespan

The lifespan of the freshwater crocodile is usually at least 50 years.

Diet

The diet of the freshwater crocodile consists mainly of fish, insects and crustaceans. The tapering snout of the freshwater crocodile is believed to be an adaptation to a diet of fish. As they are opportunistic feeders they will also prey on small animals, birds and reptiles when they are around.

They will swallow stones to help with their digestion and they only drink freshwater.

Habitat

The natural habitat of the freshwater crocodile is the Australian states of Western Australia, the Northern Territory and Queensland.

Freshwater crocodiles are generally found in freshwater billabongs, rivers, creeks and wetlands. They can live in saltwater but find it hard to compete with the bigger saltwater crocodiles.

Reproduction

Freshwater crocodiles court each other during the early part of the dry season (around May). The female will dig a hole in a part of a sand embankment to lay the eggs usually around August-September, mating occurs three to six weeks before the eggs are laid. The female will place the eggs about 12-20cm (5-8in) below the surface of the nest otherwise the eggs are at risk of being overheated by the sun. The eggs are generally laid at night.

Usually all the females within a certain area will nest within a three week period in the season, and so there can be a lot of nests in the same area. If there are too many nests in a certain area, a female may dig up another females nest and destroy it.

The average clutch size is about 13 eggs however there can be as many as 20, and the incubation period for the eggs is 65-95 days. The temperature of the nest is very important as eggs incubated at 32 degrees (89.6 f) or higher will produce male embryos, while temperatures of 20 degrees or lower will produce female embryos. A nest that fluctuates in temperature is best as it will produce embryos of both sexes. The female will try and guard the nest but a lot of eggs are taken by lizards and feral pigs. Once the young are hatched the mother will help them out of the nest and will carry them to the water in her mouth. She will guard over the young for a short period of time to guard them from predators, the exact time she does this for varies but she will leave them quite young.

Quick facts

They are not really a threat to humans unlike saltwater crocodiles, there is only one recorded attack on a human which only caused minor injuries. It is generally considered safe to swim with freshwater crocodiles as they will only attack if they feel threatened.

They have sharper, less blunt teeth than the saltwater crocodile.

All the females in a certain area will usually nest within three weeks of each other in the breeding season.

Only 1% of the hatchlings live long enough to reach maturity, and some years so many eggs and hatchlings are killed that it is thought no new adults are added to the crocodile population.