The Origin of a Species: Saltwater Crocodile (Crocodylus porosus)

Oh my God! I love it! They either appear so relaxed or full-murder, there’s no intermediate setting on a saltwater crocodile, affectionately known as a ‘saltie’. They are much broader, especially larger adults, than other crocodiles, leading some to misidentify them as alligators. Either way if they weren’t aggressively territorial and opportunistic hunters I’d hug ’em all! (Credit: pen_ash via pixabay)

I figured my Top Ten animals lists often perform quite well but I like to talk about animals, nature and wildlife often without a theme! So I am introducing a new series ‘The Origin of a Species’ in which I talk about a specific species (or possibly genus).

Today is inspired by a short bit I did for a recent article about monsters. In there I mentioned how early humans and pre-human hominids would have grown up in the midst of dangerous predators.

I included a photo of a very large boy, a saltwater crocodile, and made mention of the fact that they are one of few species that still actively hunt humans.

To be honest that’s not as scary as it might sound, frankly the saltwater crocodile actively hunts just about anything made of meat. They are a hypercarnivorous species, that means their diet is made up for 70% or more of meat, and they basically eat their food whole. Most things are smaller than a saltie.

The large boy I included in my ‘Monsters’ article. His name is Maximo and he lives at the St. Augustine Alligator Farm. What a beauty. He’s about a fifteen footer, or around 4.5m. Just chilling in the mud he looks so docile but he’s ready to spring at a moment’s notice. (Credit Public Domain)

Widely regarded as dangerous in its territory (which is basically the waters between India, Asia and Australia) it’s very much an apex predator – especially once fully grown. Females clock in at a respectable 3m in length (10 feet) and probably weight somewhere in the region of 500kg. Males, however, become very big boys, large males usually hit around 6m (20 feet) and in the region of 1,000-1,3000kg, although their maximum possible size is estimated to be up to 7m.

We’re talking 6m and a metric ton of murder. I love these guys. If you follow my wildlife stuff you’ll know I have a penchant for predators and the saltwater crocodile doesn’t mess about. They are savage.

Now, inevitable comparisons between dinosaurs and crocodiles always come up but they’re actually surprisingly distantly related. Crocodilians didn’t first show up until around 95 million years ago, only 30-or-so million years before the extinction of most dinosaurs. Their semi-aquatic nature is one of the reasons they are believed to have succeeded where most dinosaurs did not. Basically crocodilians are no more a ‘living dinosaur’ than birds are, in fact they are members of the same clade. A clade is a taxonomic group of organisms with a common ancestor, so technically crocodilians are the closest living relative of modern birds.

So no, crocodilians, even the saltie, are not living dinosaurs. I am sorry to say for all your dinosaur fans.

They are still incredible beasts, though.

The range of the saltwater croc is shown in black. (Credit:
Froggydarb CC-BY-SA 3.0)

Listed as of ‘least concern’ to the IUCN, it shouldn’t really surprise people. Despite the fact that environmental exploitation, habitat loss and (particularly up until about the 1970s) hunting for its skin for crocodile leather are common problems the relative levels of danger involved around saltwater crocs I think helps redress the balance. As far as I know they are one of few species capable of successfully biting back when we try to hunt them! I have massive respect for them for that.

So what are their numbers? It is hard to tell but estimates of the Australian population alone are between 100,000 and 200,000. Considering we’ve spoken of species before with fewer than 10,000 adults, or 5,000 breeding pairs – It’s nice to talk about a species, particularly a dangerous predator, with numbers on its side.

The saltwater crocodile is the largest living reptile on planet earth (that we know of) and, obviously then, the largest crocodilian.

They tend to be an ambush predator. I know it’s hard to think of something as lethargic and dopey looking as the saltwater croc to ‘ambush’ anything, but make my words they can put a spurt on when there’s dinner on the table and for as chill as they may seem they are always ready to strike.

It’s a surprisingly versatile hunter. It’s not called the Saltwater Crocodile for nothing and, despite the fact that it likes to spend most of its time in brackwish waters, deltas, estuarine areas, mangroves etc. it is perfectly capable of swimming great distances out at sea. This puts a diverse range of species on its menu from land animals, cattle, birds, other reptiles, or fresh and saltwater fish and even many of the sharks it shares its habitat with would not have a lot of defence if a saltie took a fancy for them.

Steve Backshall capturing a ‘problem’ saltie in his ‘Deadly 60’ show. Saltwater crocodiles habitats often overlap with humans, and one of the means we have to ensure no conflicts between the people and the crocs is to capture them and move them to safer locations, with better resources. This protects both the people and the crocodiles. You may notice the use of tape over the jaw. The saltwater crocodile is measured as having the strongest bite in the animal kingdom, however the muscles it uses to clamp down, and the muscles it uses to open up, are completely different. Whilst salties have a strong clamping bite, they have relatively weak jaw-opening muscles, so you can keep their jaws clamped shut with a bit of tape! (Credit: BBC)

We’re on the menu, too. Humans aren’t a regular part of the diet of saltwater crocodiles, with only an estimated average of 30 attacks a year (compared to several hundred attacks per year from the Nile crocodile) of which only around half are fatal. In terms of danger to humans, the Nile crocodile is by far our bigger threat however the areas the Nile crocodile inhabits are also a lot more populous so that might have a lot more to do with the numbers of attacks more than anything else.

That and, as discussed in the shark articles, frankly we’re skinny, relatively fat-free and bony. Any hypercarnivore attempting to eat us is either taking advantage of a good opportunity (e.g. a couple of people out swimming alone in the creek) or is very hungry (crocodilians are known to go a long time without food thanks to their slow digestion and metabolism).

Another similarity they share with sharks is utilisation of ocean currents to help them swim efficiently over long distances. Sometimes they even just float and let the current carry them! For as much as we want to think about them as always-alert, prowling predators I think there’s much to respect for the crocodile’s ability to just relax and literally go with the flow.

This lethargy is a common crocodilian trait, resting, relaxing, basking, chilling in the water, hunting in the cool of the night but always being ready to strike if an opportunity presents itself is, pretty much, the modus operandi of the crocodile.

It’s widely believed that crocodiles are stupid. They have one of the lowest brain mass to body-weight ratios of any animal (with only approximately 0.05% of its total mass being brain) but the truth is they just don’t need to think much. The behaviours they have are very finely honed and they are capable of learning, following changes in migrations of prey for example, surprisingly quickly.

Salties are known to breach like this for food. A behaviour most often associated with humans throwing or dangling food for them, but that it is a common behaviour would lead me to believe this is part of its ambush repertoire. When animals are feeling safe on branches 2m above the water, what better time for a croc to ambush, breach up like this, and strike!? (Credit: yaruman5 CC-BY-NC-ND 2.0)

Another thing that might be quite surprising is they are, comparatively, doting parents. Generally saltwater crocs will mate only once in the wet season, with the female laying a clutch of approximately 40 eggs. The female will select the nest site but both parents will guard it vigilantly. As a result of this guarding saltwater crocodiles experience very little predation on their eggs, with most loss accounted for by environmental factors such as flooding of nests. Female salties have also been seen helping their young to hatch (by rolling the eggs gently in their mouths) and depositing the young into the water, where she will continue to guard them.

Sadly the wilds of the water are a different ball game to the nest sites and only around 1% of all saltwater hatchlings will make it to adulthood. By the time they’re in the water they are fair game for all kinds of predators and even their own siblings. Saltwater crocodiles are viciously territorial and siblings have been known to fight the moment they get into the water.

Hatchling salties – Apparently they are aggressive from the moment they are born. Like a lot of other crocodilians their sex is determined by the temperature the eggs have been incubated at. Isn’t that incredible!? (Credit: Little Gate Publishing, used without permission.)

By the way, hatchlings are tiny and adorable. Despite huge discrepancies in their adult size, the eggs and young of saltwater crocodiles are not that much larger than their freshwater counterparts, so they come out tiny and have to grow into the monsters we might think of.

So that’s the saltwater crocodile. To some it might seem like an ugly monster, but we’re talking about a reptilian super-predator that has stood up to some of the worst behaviour humans have managed to throw at it. Once massively persecuted for their leather, and despite habitat loss, environmental exploitation and human exploitation of their prey species they continue to thrive and survive despite us. For me, any animal that manages to do that deserves respect.

A short video about saltwater crocs, watch through to the end for a short clip of a mother saltie keeping her babies safe in her mouth. So cute! (Credit: Jordan Theobold)

That about wraps up the Saltie, but be sure to check out our other Wildlife related articles here.

Published by Karl Anthony Mercer

An overly curious lovechild of Grumpy of the Seven Dwarfs and the kitsch pen section of Paperchase. Karl is on a mission to expose the seedy underbelly of academia, and thus making it appealing to wrong 'uns.

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