09/08/2026
The Australian freshwater crocodile (Crocodylus johnstoni), often simply called a “freshie”🐊. Smaller and much less aggressive than the estuarine or saltwater crocodile, freshwater crocodiles are an important predator in the river ecosystem and are regularly seen basking along the banks or floating quietly near the river's edge during the dry season when water temperatures are below 27 degrees.
The Upper Ord has historically supported an exceptionally large population of freshwater crocodiles. This is partly a consequence of the construction of the Ord River dams. The Diversion Dam created Lake Kununurra in 1963, while the Ord River Dam created Lake Argyle upstream. These permanent bodies of freshwater provided extensive habitat for C. johnstoni.
Historical surveys give us a fascinating glimpse of just how abundant they became. In 1989, spotlight surveys estimated approximately 7,500 non-hatchling freshwater crocodiles in Lake Kununurra and around 25,000 in Lake Argyle. The WA crocodile management program cautioned that the Lake Argyle estimate may have been high, but subsequent spotlight and helicopter surveys continued to demonstrate a very large population, with Lake Argyle considered to contain 10,000 or more freshwater crocodiles.
Then Came the Cane Toad 👎
An important complication when discussing crocodile numbers today is the arrival of the cane toad (Rhinella marina) in the East Kimberley.
This matters because freshwater crocodiles will attempt to eat cane toads. The toxins contained within a toad can be lethal to a crocodile, and studies elsewhere in northern Australia have recorded dramatic population declines following invasion. Research on the Victoria River system in the Northern Territory, for example, recorded declines of up to 77 per cent in some freshwater crocodile populations after cane toads arrived.
However, the effect is not the same everywhere.
This makes the story of the Upper Ord particularly interesting—but it also means we need to be cautious about quoting historical population estimates as though they represent today's population.
What Do We Know About Crocodile Numbers Today? 🤔
This is where there is an important gap in the story.
The Upper Ord and Lakes Kununurra and Argyle were subject to extensive crocodile surveys during the late 1980s, 1990s and early 2000s. Those surveys provide excellent historical baseline information. I have not been able to locate an equivalent, publicly available long-term survey dataset for the Upper Ord/Lake Kununurra population following the establishment of cane toads that would allow a reliable comparison with those earlier estimates.
Consequently, figures such as the historical estimate of 7,500 freshwater crocodiles in Lake Kununurra should not automatically be presented as the current population.
As a regular operator on the Ord River, I have seen many dead freshwater crocodiles and the larger crocs are no where near in abundance as they once were. Big wet season rains have washed away vital nesting grounds in some places for the crocodiles making it difficult for population growth. What we can say with confidence is that freshwater crocodiles remain a characteristic part of the Upper Ord River ecosystem and are still regularly encountered. What is much harder to quantify is how their overall population and age structure have changed since cane toads became established in the East Kimberley.
That distinction is important. Seeing plenty of crocodiles does not necessarily tell us whether the population is the same as it was 20 or 30 years ago. Long-lived animals can remain conspicuous even when recruitment or survival in particular age classes has changed.
