Wild - 50 years
Captive - 50 years
Australia's Slender Snouted Crocodile!
The freshwater crocodile is the smaller of the two crocodile species which naturally occur in Australia with the other being the saltwater crocodile. They reach a length of up to 3m (9.8ft) long.
These animals are efficient predators who hunt fish, crustaceans and insects in the waters of Northern Australia. To aid in their digestion they will swallow stones.
Appearance - What does a Freshwater Crocodile look like?
The freshwater crocodile is a light brown colour with darker bands on their bodies and tails. On the belly they are coloured white.
The body scales are quite large and the back has wide, closely-knit armoured plates.
They have a narrow snout which has 68-72 very sharp teeth inside.
On each leg is a webbed foot and the body ends with an incredibly powerful tail. Their eyes have a special clear eyelid which protects the eye while they are underwater.
The freshwater crocodile is one of the smaller crocodile species. These animals are considered sexually dimorphic meaning males and females differ in their appearance.
Males can grow up to 3m (9.8 ft) long and females up to 2.1m (6.9 ft), however the average size of these crocodiles is about 1.5m (5ft) long. They are slow growing animals and it usually takes a male about thirty years to reach 3m long. Males weigh 60kg (132.3lbs) while females weigh about half of that at 30kg (66.1lbs).
In upstream escarpment habitats individuals typically weigh 10% less than individuals found downstream.
Adaptations - How does the Freshwater Crocodile survive in its habitat?
This species is well adapted for life in the water. Their eyes and nostrils sit high on the head allowing them to sit above the rest of the waterline while the remainder of the body is safe below the surface.
When diving below the surface the freshwater crocodile has a nictitating membrane. This is a clear membrane over the eye which closes to protect the eye below the water while still allowing the crocodile to see.
Diet - What does a Freshwater Crocodile eat?
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. Recent research has seen
Adults have been known to feed upon the juvenile crocodiles.
They will swallow stones to help with their digestion. They only drink freshwater.
Range - Where do you the find the Freshwater Crocodile?
Australia is the native home of the freshwater crocodile. Here they can be found in the states of Western Australia, the Northern Territory and Queensland.
Habitat - Where can a Freshwater Crocodile survive?
Freshwater crocodiles are generally found in freshwater billabongs, rivers, creeks and wetlands. A small population inhabit a river within the Tunnel Creek Cave in Western Australia.
They can live in saltwater but find it hard to compete with the bigger saltwater crocodiles. In some areas the two species will occur alongside one another.
Reproduction - How does a Freshwater Crocodile produce its young?
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. Laying typically takes place 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 predators.
Once the young hatch 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.
Behaviour - What does the Freshwater Crocodile do during its day?
They are not really a threat to humans unlike saltwater crocodiles, there is only one recorded attack on a human which on caused minor injuries.
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.
In areas where there is not water year-round freshwater crocodiles will spend the time from late winter to late spring dormant in a shelter dug in to the creek bank.
Adults can produce a wide range of vocalizations including a roar, bellow or hiss.
Predators and Threats - What stops the Freshwater Crocodile from surviving and thriving?
Adults have very few predators. They are eaten by other crocodiles and hunted by humans.
They also attempt to eat introduced cane toads which can lead to poisoning. Despite this they have persisted in areas with large cane toad populations for many years. Cane toads have also led to decreased numbers of monitor lizards which were a key predator of freshwater crocodile eggs. With the decrease in monitors an increase in freshwater crocodile hatchlings has been seen.
Cane toads may have assisted this species as they reduce varanid (monitor lizards) populations which are a main predator of this species.
Their population is considered stable across their range.
In some areas they may become entangled in a fishing gear causing them to drown. Degradation of water courses is also increasingly impacting this species.
Previously they were hunted in large numbers for the skin and the stuffed specimen trade. This continued until they were offered legal protection. Small numbers are farmed but the low quality of the skin has made this uncommon.
In some areas across Australia the species may be kept as a pet and small numbers are traded for this. Most of these individuals are taken from farms and other captive centers.
Other names for the freshwater crocodile include freshie, Johnson's Crocodile or Johnstone’s Crocodile.
The freshwater crocodile was first described for modern science by Krefft in 1873. It was intended that the species would be named for Mr. Robert Johnstone but this was misspelt as johnsoni. Overtime this has lead to confusion over their scientific name though in 1983 the name was formally updated to Crocodylus johnstoni by Cogger et. al.
Crocodiles have existed mostly unchanged for over 200 million years.
Swanson, S. and Parish, S., 2011. Field Guide To Australian Reptiles.
Webb, G.J.W. and Manolis, S.C. (2010). Australian Freshwater Crocodile Crocodylus johnstoni. Pp. 66-70 in Crocodiles. Status Survey and Conservation Action Plan. Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.
Somaweera, R. et al. (2018) “Observations of mammalian feeding by Australian freshwater crocodiles (Crocodylus johnstoni) in the Kimberley region of Western Australia.” Perth: Western Australian Museum.
Somaweera, R., Sonneman, T. and Woods, D. (2014) “A note on the Australian freshwater crocodiles inhabiting Tunnel Creek cave, West Kimberley.” Perth: West Australian Museum.
2nd ed. New South Wales: Pascal Press.Environment | Department of Environment and Science. 2011. Freshwater Crocodile. [online] Available at: <https://environment.des.qld.gov.au/wildlife/animals/living-with/crocodiles/about-crocodiles/freshwater> [Accessed 25 April 2020].
The Australian Museum. 2020. Freshwater Crocodile. [online] Available at: <https://australianmuseum.net.au/learn/animals/reptiles/freshwater-crocodile/> [Accessed 25 April 2020].
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