ExtinctZoo - How Crocodiles Survived The Ice Age

Episode Date: April 4, 2026

How Crocodiles Survived The Ice Age

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And you can tell this by the giant blocks of ice that exist year round in the north and south poles. As in a general sense, as long as there's permanent glaciers and ice sheets on the planet, many consider that good enough evidence for that an ice age is occurring. And this particular one began about 34 million years ago during the Eocena-legacine boundary. After Antarctica can move south enough, got a new cold current, and froze, leading to a domino effect, and the rest is history. So, in other words, it's been happening for a while. Of course, though, like anything, the intensity of this event has fluctuated from the start, with some parts of the ice age being pretty tame, while others got pretty sketchy,

and this included a few smaller events within, such as the last glacial maximum, a period where the ice sheets reached their maximum extent. And this sub-event, if you will, happened much more recently in time, you might believe, a bit over 30,000 years ago, give or take, with global temperatures dropping over 6 degrees Celsius or 11 degrees Fahrenheit, and thus leading to an expansion in the ice. And even during the summer, it's believed that 25% of the Earth's land could have been covered with ice, with ice sheets expanding over much of North America, Europe, and even small parts of Asia and South America.

And these ice sheets were absolute monsters, at least in size, being up to 4 kilometers or 2.5 miles thick, which is for reference nearly five times the height is the world's tallest building and thus resulting global sea levels dropping by quite a bit and making the world look like this on a map. Now again, this is just one extent of extreme cold, which as far as we know seems to have been the most severe spell, representing the coldest point the Earth has been for possibly a few hundred million years, maybe even more. Yet with that said, it does seem that there was multiple similar cold spells sprinkled throughout.

And so unsurprisingly, this extreme climate mixed in with the physical ice sheets, impact on sea levels, and the change of environments, led to many animals perishing directly. or indirectly due to the Ice Age. In one group that suffered many losses, it underwent a significant paradigm shift, if you will, was our cold-blooded pals, the reptiles. Now prior to the Ice Age, reptiles had been doing surprisingly well, contrary to what the Sinozoic's nickname, The Age of Mammals, may have you believe. And actually, in various continents and bodies of water, reptilian groups their top dogs

around, not mammals. Not to mention that many were seriously giant, such as the sea serpents, terrestrial snakes, Crock, Sepachids, and the list goes on. And their size was probably things with the warmer temperature seen in the early Sinozoic, especially during events such as the Eocene Thermal Maximum, which was a bit like an extended summer. And all this heat aided reptiles growing bigger, as with their cold blood in nature, it's much harder for reptiles to generate their own body heat compared to mammals. And thus they rely on external factors. So when things are warmer, they have to worry less about that requirement, and also allows them to perform other functions better and preserve more energy.

In contrast, when things get really cold, they tend to suffer. And studies have found that the Ice Age heavily impacted the overall size of reptiles as well as their extinction rates. With studies on certain islands throughout the Ice Age, for example, finding that numerous reptiles simply cannot withstand the changes. And then when you add in the fact that a colder environment typically means less productive environment as well, meaning less prey, it's no surprise that the bigger reptiles struggle the most.

And so, with all this said, the reptiles of today are typically much smaller than those of old. However, if you take a look at every group, you'll find one that is strangely resisted bending to the cold, so to speak, and are a pretty unlikely survivor of the Ice Age, as they are known to Love Heat and are still absolutely massive, occupying eight of the top ten spots for the largest reptiles on Earth from a weight standpoint, and the largest of them is literally ten times bigger than the largest snake. And of course, I'm talking about crocodiles, or rather crocodilians. Yeah, these carnivous reptilians are among what I think would be the strangest survivors

of the Ice Age. I mean, we lost things like Sabretoothed cats, various alphanids, etc., etc. But crocodiles? Nah, they made it out. And this does lead to a rather interesting question of how did crocodilians of all things actually survive the Ice Age? And as it so turns out, it wasn't just one thing that saved them, but a few, with the only true single statement being that they are simply built different. They are truly wonders of evolution. And you have to remember that modern crocodilians, i.e. members of the order crocodilia, had already survived some pretty messed up stuff prior, such as the KT extinction event, which, as you may know, killed all the non-avian dinosaurs, yet the Crocs somehow brushed it off and were among Earth's largest

survivors, despite the fact that the planet got a bit chilly afterwards back then as well, you know, with all that ash and dust blocking out the sun. So basically, these guys have survived asteroids, mass extinctions, ice ages, you name it. And yet they're still here. And their survival through that event, and the Ice Age, are in some ways a bit linked, as Crocs use some of the same traits to creep by both events, including one that simply had to do with their lifestyle. As you may know, crockies are very fond of water, having evolved to be semi-aquatic, and many can stay submerged for long durations of time, with each having evolved unique ways

to maximize their breath, including drastically slowing down their metabolism and in some cases even utilizing a specialized heart shunt that helps redirect oxygen from the lungs to vital organs. And all this doesn't include the simple fact that they can also just chill on the surface of the water if they want. And this is all to say that crocodilians do just fine in water, and don't often need a leave, helped them a lot during the Ice Age. As contrary to what a hot or cold bath may have you believe, water is actually very hard to heat or cool, relatively, essentially requiring more

energy to change in aquatic environment than a terrestrial one, and thus spending large amounts of their life in the Agua helped crocodilians. As the longer time it took for the temperature to change in the water, the better it allowed populations to deal with climate shifts, whereas on land, the shifting climate could have been more severe, sudden, and drastic. Additionally, throughout the Ice Age, certain watery environments did seem to be more stable than other environments. when it came to the food chain, with collapses being less common, which helped keep crocodilians nice and plump. And that was, and still, is another key advantage of crocodilians. As simply put, crocs are not picky eaters. I mean, I guess you could argue that some kinds, such as the

gharials, want sushi only, but generally speaking, this group eat about just whatever they can. I mean, there is a reason why crocodiles are one of the few animals considered to be natural predators of humans. If it moves, it's game. And the same largely goes from members of the the alligator a day too. I mean, just take a look at the American alligator, who's known to eat everything from insects all the way up to cattle with the opportunity presents itself. And because of this generalistic lifestyle, crocodilians weren't as heavily impacted as others when a few animals vanished here or there, or when a new species popped up every once in a while. And it certainly helps that these guys possess some ridiculously overpowered offensive and defensive

capabilities that allow them to compete with pretty much most animals evolution throws with them. For starters, many crocodilians have evolved giant, robust, monstrous skulls capable of dishing out ridiculously high bite forces, with the saltwater crocodile actually holding the title for the strongest bite force on the planet currently, at least from verified tests, with one study measuring a bite to over 16,000 newtons in force, which is easily more than enough power to shatter your femur, the strongest bone in your body. Then on top of having ridiculous bites that can crush bone, the vast majority are also capable performing the infamous death roll, including some garials even.

Where in a croc will bite down on its prey, hold onto it like your mom might have pinched your ear, and then we'll start to spin continuously, using their powerful tail for rotation, which allows them to tear massive chunks of flesh off, or many times even limbs. So as you can see, and as you probably knew, they've got quite the ability to kill, and then on the flip side, they themselves are not the easiest to kill. Seeing that this group has homemade built in armor, which comes in the form of seriously tough skin, scales, and boating scutes, known as osteoderms, to lay underneath their epidermal scales

and provide these creatures an immense level of durability. And I think one real-world example that shows us pretty well is a recent story about an Australian. It's always them, isn't it? And one day, said Australian was nicked by a crock while walking near the water. Lucky for him, though, he... Ambition comes in all shapes and sizes.

At First Citizens Bank, we roll with your goals, because we're built for what you're building. fit for your ambition for citizens back. Get a knife, which he used to stab the crock out repeatedly in the head. And while the croc did let go, it was perfectly fine, minus a few superficial scrapes in the blade, which mind you was on the larger size, not a butter knife. And this level of defense and offense has made these guys nigh untouchable and ridiculously hard to get rid of, a benefit to have wherever, whenever, and especially during a time of heightened hardship,

and final turnover is high. But with this said, one of the biggest reasons why we're not going to be able to be able to get rid of, But Crocodileans made out of the Ice Age actually has nothing to do with their physical features, rather just simple geography. As for the most part, they simply stayed away from where the ice was. To be a bit more specific, while movies and documentaries may have you believe the Earth was a giant snow globe during the last glacial maximum, it wasn't. Some areas didn't even have ice or snow, with warm and tropical areas still existing, albeit these regions were a bit more limited than presently, with these two maps showing the difference between now and the last glacial maximum. And as you can see, while yes there was much more ice prior, hot spots definitely remained.

And if you take a look at where crocodilians are found today, you can see that their global range aligns pretty well with where the ice was absent thousands of years ago. However, this isn't to say that all of them got off scot-free, seeing that during warmer interval periods, some species, such as the American alligator, were known to live closer to the poles than they do now. And when things started to get a bit too cold, they did see a reduction in their range, and a drop in overall population. But with this said, don't let this take away from the impressiveness of the situation.

As again, all places did see drops in temperature, tropics included, and multiple kinds of crocodilians did in fact experience and survive at least temporary freezing conditions, conditions that would likely kill most other large reptiles. The head crocs have some pretty nifty tricks of their sleeves, or scales, that they bring out when things get a little chilly. And one of the coolest examples of this, no pun intended, is seen again in the American alligator, which has developed a pretty nifty ability known as formation. Think of this as being like hibernation in a way, but still different. And essentially what it is, is that when things get too cold for alligators, and for other animals that brumate, they will go into a state of dormancy, where their metabolic rate will drastically slow down and they will become extremely lethargic. And in this state, they won't fall into

a complete slumber, but they will stop doing certain activities, such as eating. Whilst on the flip side, they will keep up drinking in order to stay hydrated. And so obviously, this slowdown allows them to conserve energy and store resources for when it's really needed. things get exceptionally cold, they've also been known to construct mud holes that add a little extra warmth, and not to mention shelter, which during the ice age would have been a bonus during any winter storm. And to go along with brumation, gators have another funky trick as well, which consists of transforming their snouts into biological snoracles.

Even now, if water freezes over, and you live somewhere with gaiters, you might see a gator or two sticking your little snouts out through the ice while the water around them freezes, and thus allowing them to stay a bit warmer, allowing them to stay submerged without the need to get out of the water to breathe, and thus keeping them a bit warmer. And while not as adapted for the cold, other crocs have some dandy tools as well, they can help make cold spells a bit more tolerable, and this includes timing their days, as they will shift activities to make the most of the small pocket of warm weather, while planning nothing, so to speak, when it's gloomy.

Then during integral activities, such as basking in the sun, they are able to flatten their skin in order to increase surface area, and this increased amount of sunlight they're exposed to. And we're looking at specific species, we see that some types of the same types of the the Mugger crocodile have been known to slither into burrows when it's cold, while Nile and saltwater crocs take advantage of their usually larger environments by swimming into the deeper areas, where the water is less impacted by the cold air. So clearly, it seems that this group has not one, but a few tricks to pull out when the going gets tough.

And that's what makes them so crazy, the fact that crocodilians have this huge array of tools, whereas some other animals only have one or two to help out. And even with all this, there is still more madness that help them out than Ice Age. I mean, take a look at a large saltwater crocodile, for example, an absolute unit, which can weigh over two tons. And with this size, you'd expect it to need to eat a cow every single day just to survive. And yet, many times, adults in zoos, for example, are given less than 100 kilos or 220 pounds of it per, per year. Wait for it, year. Yes, year.

220 pounds or 100 kilos per year. While an American person, on the other hand, eat closer to a ton of food, despite being about 10 times smaller. And this isn't some sick form of torture done by zoos, it's just that Crocody Lane's have crazy slow metabolisms that allows them to survive without food for multiple months if need be. And they also possess extremely efficient digestive systems that leads to almost no energy from their food going to waste. And as a result, during an ice age, when the mere thought of hunting and the cold sounds horrible, Croxon just give a sigh of relief and stay in the nice warmth, thanks again to their

metabolisms, which allow for some much-needed flexibility. And to make the situation even better, when they do eat, they can still eat a poop load if they need to. So unlike a human that may be starving, finds a giant carcass and then can only eat some of it, a crock can eat huge portions, with some species being capable of devouring half their body weight in one go, which is, for reference, like an American eating 14 full-sized chickens in one sitting. So yeah, a lot of food. And then, to really seal the package with their already energy-saving kit, Crocody Lane's mainly killing a fashion that's not very taxing.

Like, for example, let's say you find yourself in the Ice Age and you need to go get some food. Well, that's going to be a whole process. You're going to need to gear up, get out there into the cold weather, trek around and hopefully find some tracks, track said animal, kill said animal, and then if you succeed at that, you now have to bring the meat back to home base. So kind of a involved process. Whereas in the crocodilians case, the food just usually comes straight to them, like Uber Eats. As again, they live in the water and all animals got to drink, allowing them to utilize ambushes were only a quick burst of power. is needed, not much more. And this was a huge deal in the culture days, as though for all these

adaptations allow the group to take as much energy as they could, whereas others still to operate at full capacity just earn a snack. And then to pair with the impressive ability that allows them not to eat for a long time, Crocodileans have also evolved to be highly resistant in low-oxygen environments, which doesn't just let them hold their breath for a long time, but thrive in more environments, giving them a wider range of places to live, which is nice when half of the world is already off-limits due to the ice. But what may have been an even bigger advantage over their ability to avoid oxygen, or with their ability to beat up pathogens. And what I mean by this is that crocodilians are not only resistant when it comes to taking

damage and being messed up, but they're also highly durable from an immune system perspective, with their innate and adaptive systems being much stronger in what's typically seen in mammals, for example. And this is partially thanks to their blood, which contains very high concentrations of multiple antimicrobial peptides that allow them to get rid of numerous bacteria, viruses, fungi, and parasite, with it in fact being so potent that in one study where they introduced alligator blood to human blood that was teeming with HIV, the HIV was completely eradicated once the crocodile blood entered the scene. And so, the advantage of having a powerful immune system is pretty obvious, but it might have

been especially helpful during the Ice Age, as with the fall into global temperatures, colder conditions can negatively impact immune systems defenses, resulting in it being a bit weaker than normal. And crocodilians can not only get over sicknesses quite quickly, but also general injuries as well, as their regenerative capabilities are almost in par with their immune systems. Wounds they sustain not only clot exceedingly fast, but can also be observed fully healing within a few days, and they've also been seen to partially grow their tails too. And this again is an advantage in general, but it's especially useful when everything is going

to H.E. double hockey stick. Or maybe the opposite of that? Either way, when you combine this with every other trait I've talked about, you realize that crocodilians survived essentially because they are superhuman, or super animal rather, and then also because they had prime real estate. And truthfully, there are other reasons for their survival too, which I just didn't mention, as Crocs are really just one of the most metal creatures evolution has yet to cook up. And there's a pretty good reason why throughout Earth's history, many animals at Croc-like builds and lifestyles. It's just that darn Opie. Thanks for watching, and until next time, on Extinct Zoo.

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