Saltwater crocodiles are formidable apex predators.
There are so many of these crocodiles on the north coast of Australia,
that you can’t go far without seeing signs warning you of their danger. But only 50 years ago,
this king of the waterways was almost extinct. This is how they’ve bounced back.
This is the saltwater crocodile. It’s the largest reptile on earth and ferociously territorial.
Adults can grow to around 6m, and weigh 1000kg. Australia actually has 2 species of crocodiles -
the saltwater crocodile and the smaller freshwater crocodile - also known as salties and freshies.
In Australia, saltwater crocs are found extensively across the north coast.
They live in rivers, wetlands and swamps, and can travel out to sea or along the coast. The majority
of salties live in the mangrove-rich waterways of the Northern Territory.
The Territory has the most crocodiles and keeps the best data, so that’s where we’ll focus.
Given the ubiquity of crocodiles in the Territory today,
it’s hard to imagine that only 50 years ago they were under threat of imminent extinction.
In the mid-20th century, crocodile skin was very fashionable. This made crocodile hide incredibly
valuable. From 1945 until 1970 there was an intense period of hunting crocodiles for their
skin, as many people capitalised on this gold rush. Crocodiles were relentlessly killed, their
skin being exported to high end designer brands. Finally, in 1970 their numbers had dwindled enough
that saltwater crocodiles became protected in Western Australia, and the NT and
Queensland followed suit a few years later. But after a couple of decades of over-hunting,
the crocodile population in the Northern Territory had been thoroughly obliterated,
and was down to only about 3000 non-hatchling salties. Crocodile numbers are usually counted
as the number of non-hatchlings, because while breeding females lay around 50 eggs per year,
only 1% of hatchling crocodiles are expected to make it to adulthood.
Baby crocodiles are tiny, and routinely get eaten by birds, fish, and other crocodiles.
With only a small pool of crocodiles left, it wasn’t guaranteed that the population numbers
would recover. Conservation efforts were started and it was hoped the salties could bounce back.
And bounce back they did. Today there are up to 200,000 saltwater crocodiles in Australia,
and the Northern Territory is home to at least 100,000 of these, up from the nadir of 3000.
Crocodile monitoring is routinely undertaken on various rivers throughout the NT. Here are
the results for the Adelaide River, showing that we’re basically back to peak crocodile on
this particular waterway. Unlike some other apex predators, saltwater crocs are far from rare. In
2020 there were 4 non-hatchling crocodiles spotted per kilometre of river surveilled.
In fact, crocodiles have been so successful at replenishing their numbers that they’re now
routinely removed from areas of human population. Darwin, the capital city of the Northern Territory
is home to around 150,000 people. In the last 10 years, an average of 279
crocodiles per year are removed from waterways around Darwin. That is a crocodile caught and
removed on most days of the year. 98% of the crocodiles removed are saltwater crocs.
Their average length is well in excess of 2m. Imagine living in a city around which most days
a 2m territorial terror full of teeth is trapped, hopefully before posing any danger to people.
And crocodiles haven’t just increased their numbers - they’re also getting
bigger. Crocodiles can live a really long time - like, 70 years long. It takes decades for them
to reach full size. That means that most of the crocodiles hatched in the last 50 years
are still growing up. Remember that graph of the Adelaide River that showed the number of
crocodiles is plateauing? Well here’s a graph of the same river that measures
kilograms of crocodile per kilometre. In other words, how big the crocs are.
And crocodiles are huge in the territory in more than one sense. They’re also big business. The
wild population has rebounded so much, that it now supports harvesting of crocodile eggs
for farmed crocodiles. Companies are still making bags and clothes from crocodile skin,
and in 2016 59,000 skins were exported. And that’s not to mention the extra tourism that
these impressive crocs bring to the region. Not only has the conservation of saltwater crocs been
successful for business and tourism, but a healthy crocodile population also benefits the Territory’s
groups of aboriginal people, who aren’t bound by the hunting protections, and can continue to
hunt crocodiles in the Top End as they’ve done sustainably for tens of thousands of years.
So that’s how the largest reptile on earth was put at risk of extinction only 50 years ago,
and how in a remarkably short time their numbers have increased by at least 30-fold in the NT. It’s
a conservation success story, and its definitely a reminder to take any warning signs seriously.