The Conscious Crocodile

My wife, Susan, claims to be afraid of crocodiles.

I find this charming, because it brings to exactly three the number of things I can name that Susan is afraid of. The other two are bears, because she’s been attacked by one, and clowns, because—well, that one needs no explanation.

But I’m not sure I’m buying her profession of fear where crocodiles are concerned. For one thing, it hasn’t kept her from kayaking among them on two occasions I can name (and probably a few we weren’t aware of). And also, when I spotted the crocodile in the photo at right, from the deck of the Casa Cenote restaurant a little south of Akumal, it was Susan who gleefully grabbed my iPhone and set out to see if she could get a little closer for a decent snapshot.

Can you find the crocodile in this snapshot?
Photo by Susan Fry


I say when I spotted it—actually nothing happened until a good five minutes after I spotted it, because I just sat there for the longest time not saying a word. You see, my life has been a cyclical process of painfully gaining a little credibility, and then squandering it all in a flash by saying something radiantly stupid, so my brain has stepped in and developed a defense mechanism to protect me from that. My brain now requires redundant fact-checking, and re-analysis from multiple perspectives, before it will allow my mouth to open and say something like, “Hey, guys, there’s a crocodile on the beach.”

I finally said it, though, and all the heads turned.

“Just past those sunbathers there. See it?”

Everyone peered out where I was pointing.

“Look about a hundred feet beyond that woman without the, uh, whatever you call that thing she’s not wearing.”

Everyone squinted.

“It looks a lot like the rocks. Really, it’s there.”

I thought I’d gone and done it again, but finally someone said, “Oh my God, he’s right!” and I sighed and sat back, saved again.

My assessment of how scary crocodiles are isn’t as interesting as Susan’s, because I’m just a normal guy with a whole closetful of normal fears, but for what it’s worth, I have to agree with her: There’s something about a crocodile. They slip into the water and you don’t know where they’ve gone, they attack from below, they have reptilian brains and vertical pupils and they look largely like they did when dinosaurs were walking the earth. There’s just something about the crocodile that makes you shudder. But to me, what is most unnerving about them is not that they are brute, prehistoric, instinct-driven killing machines.

It’s that they’re a lot smarter than you think they are.

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A while ago when an asteroid seven and a half miles across hit the earth 150 miles northwest of Akumal, everything large that was walking on the surface of the planet perished except the crocodiles. They were the largest vertebrate to survive that extinction event. So although they are classified as reptiles, scientists will tell you they are more closely related to dinosaurs and birds than they are to modern reptiles, and one thing they have that lizards do not is a cerebral cortex.

That makes them capable of a whole range of things that don’t seem terribly brute. They can do pattern recognition. If you’re an animal who tends to come down to the water’s edge at around the same time each day, they’ll figure you out, and lie in wait for you. If you’re lucky, the nostrils and eyes might be showing, but they might also be completely submerged, which is something they can do for up to fifteen minutes routinely, a couple of hours in a pinch. When the herons are building nests in the mangroves, they will decorate their snouts with sticks and twigs—and they know exactly what types sticks and twigs the birds are looking for. When the heron lights briefly to grab a choice one, that’s the end of that story. They can hunt cooperatively, circling around schools of fish to concentrate them, and then taking turns lunging in for a bite; or bringing down a large animal as a group effort, with one crocodile holding it down for the others to dismember. They have elaborate mating rituals, and a complex communication system involving a variety of sounds including chirps, whistles, hisses, and a low-frequency mating “bellow.” They are devoted and fiercely protective parents. They have the most complex behavior of any reptile, and they can be very social—but only when they’re in a social mood. When they’re not, there can be cannibalism. One nine-foot crocodile was found in Honduras with a five-foot crocodile in its stomach. Of the same species.

American Crocodile (Crocodylus acutus)
By Mattstone911 (Own work) CC BY-SA 3.0 via Wikimedia Commons


When you read up on crocodiles, half the articles you come across are biased one way or the other. They are either edge-of-the-seat thrillers about what savage killers they are, or they are fru-fru pieces about how they’re actually caring, intelligent, misunderstood and in need of a hug. Clearly what’s being provided by these articles is a look into our own minds. So what I’m going to try to do here is write a clear-eyed article about crocodiles. Open your round pupils and enjoy, because they are absolutely amazing for exactly what they are—and are not.

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The crocodile we get here on the Caribbean coastlines is the American Crocodile (Crocodylus acutus), and they’re not that hard to see around here. They love mangroves, estuaries and river mouths, so Sian Ka’an is great crocodile habitat. There’s a good-sized one that hangs out in the mangroves beneath the Boca Paila Bridge. They can approach twenty feet long and a couple thousand pounds, but fifteen feet is more normal. If you’re like most people who see that photo up there, you were surprised that a crocodile would be friendly enough with saltwater to hang out on a beach. Well, don’t feel too out-of-step—scientists hadn’t fully appreciated it either until fairly recently. It was always known that they sort of tolerated a little brackishness out of necessity, but it’s becoming more clear that they actually prefer it, and that they are full-on marine animals, with desalinators under their tongues, and the ability to make a living on tiny cayes and islands without a drop of fresh water around. They’re also learning that they can navigate long distances at sea. A hybrid of the American and the Cuban crocodile recently showed up in Cancun, and the only place those hybrids exist is in a swamp on the south coast of Cuba. Just the strait between Cuba and Cancun is 125 miles of open water. They also seem to have homing skills, and relocated crocodiles have returned 250 miles to their childhood stomping grounds.

Their mating and child-rearing behavior is a wonder, and amazing by reptile standards. They’ll start courting with the bellowing I mentioned, and when they find each other the male will do some head-slaps. If the female is turned on by this, she’ll arch her head and tail upward, and then the male vibrates his entire body in a complex display. Then they rub snouts, ride each other around, blow bubbles and seemingly have a great, playful time of it, and finally the male grasps her from the side, everts his penis, which was tucked inside him but is constantly erect, and he penetrates her.

When she lays the eggs (there will be from 30 to 80 of them), she digs a nest for them, and it’s worth remembering that she will usually be in a burrow nearby, ready to defend them. You’d think that would give pause to the nest raiders, but the mangroves are just full of animals ballsy or hungry enough to try it, and raccoons, coatis, foxes, skunks, vultures and iguanas are all known to give it a shot in a pinch. With mixed results.

And this is my favorite part: They will often cover the nest with vegetation, which will generate heat as it composts. I kid you not—they know how to build a compost heap. I’ve been trying to make a compost heap work since the seventies, but the crocodiles have had it dialed in since the Cretacious. The reason for this trick is that crocodiles do not have sex chromosomes. Instead, sex is determined as the fetus develops in the egg. Each fetus can go either way, and it’s controlled by temperature. At 86 degrees Fahrenheit and below you’ll get mostly females, but by 91 or 92 you’ll be getting mostly males, and evolution just hates single-gender situations, so the crocodiles carefully avoid a one-gender clutch.

When the eggs are ready to hatch, the babies will call out to their mom from within the eggs and the mother will assist them in breaking out, by rolling them around in her mouth, and then she’ll carry the hatchlings to the water, and continue to watch over them and even feed them for several weeks. If she’s not around the male may step in.

She may also carry the hatchlings some distance, even a mile or two, to get them to a good, safe nursery habitat. They will be in her mouth, peering out from between her teeth. The hatchlings have a ton of predators, but I guess there’s not a much safer place to be than inside the mouth of a large crocodile, depending on your relationship with the crocodile. Crocodiles are better at travelling overland than you might think. With their “belly walk,” which is a slithering motion with their legs out to the sides, they can hit eleven miles per hour, which is roughly as fast as you can run. But they also have a “high walk,” in which their legs are under them and their bodies are off the ground, and some species can even gallop. But really they are at their best in the water, where they accelerate with their tails, brake with their webbed feet, and are capable of powerful lunges and speeds of twenty miles per hour.

They are nocturnal, which is why they have vertical pupils. Vertical pupils are an interesting adaptation—they actually evolved to help night hunters get through the day—they are better at excluding light from those extra-sensitive eyes. Their eyes have rods and cones, so they probably see in color. They tend to hunt in the first few hours of darkness, and they prefer moonless nights. They will lurk by a shoreline with nothing showing but the tiny bumps of their nostrils and eyes, and explode out at prey that comes down to the water’s edge. They prefer medium-sized mammals, reptiles and fish, but they’ll take down a large animal if they need to, including deer, peccaries and livestock. They have four-chambered hearts (also rare in reptiles), a high level of control of the oxygenation of their blood, and when they stay submerged for longer periods, they slow their hearts to a few beats per minute and shut down blood flow to non-essential organs. By the time they attack, their blood might contain mostly CO2, and then they do something extremely cute: They close a valve in their heart called the aortic arch, with the result that all that CO2-rich blood floods directly out of their muscles into their stomachs, and all that CO2 hugely increases the acidity of their digestive juices. They have the most acidic stomachs of any vertebrate, and can easily digest things like horns, hooves and turtle shells.

And it is absolutely true that they are fairly fearsome creatures. They have by far the most powerful bite of any animal, whether mammal, reptile or fish. There are five thousand pounds of force in the jaws of an American crocodile, and if you think that’s scary, be glad you weren’t around in the Cretacious period. Their ancestor Sarcosuchus lived in the lush, green wetlands and river systems of what is now the Sahara Desert, and it kept growing all its life (it’s called indeterminate growth), and could reach forty feet and ten to fifteen tons, and scientists think it probably had a bite force of twenty-three thousand pounds, from what they can tell by analyzing fossil jaw structures. That’s more powerful than any dinosaur, including Tyranosaurus Rex, but hey, T. Rex was not the largest meat-eating dinosaur that ever lived. That would be his relative Spinosaurus, who actually co-existed in those Saharan wetlands with this crocodile, and competed with him for prey. Scientists think there were probably some epic battles between the two that Steven Spielberg would have loved to film.

By Matt Martyniuk Dinoguy2 (work done by author) [CC BY-SA 3.0 (], via Wikimedia Commons


But for all that bite force, there are a couple of abilities crocodile jaws don’t have. They can’t shear meat. All their teeth are dagger-shaped things that hold but don’t cut, so they kill their prey by clamping down on it, which their jaws are very good at, and then rolling to rip it apart. People call it the death roll, but death is not instantaneous, and usually comes only through bleeding or drowning. As death by a predator goes, there are easier ways to die. A crocodile killing is, well, messy and protracted.

The other thing their jaws are not good at is opening. They are fearsomely good at closing them—most of the bulk you see in a crocodile’s head is those muscles, and they say that when you touch them they feel like bone—but the jaw-opening muscles are tiny, which is why researchers can safely work with a large crocodile by simply taping its shout shut. (Of course, getting that tape around the snout is a dicier proposition.)

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So on to the big question: Are they dangerous to humans? The answer is yes. They definitely are. The Nile crocodiles of northern Africa and the saltwater crocodiles of Australia are worse, but American crocodiles are plenty worthy of respect. There have been 36 crocodile attacks in the Cancun area since 1995, though fatalities are rare. Most are in the Nichupte Lagoon, which is the large body of water between the hotel strip and the mainland. There are warning signs all up and down that road. To stay out of trouble with crocodiles, all you really need to be is non-stupid, but that doesn’t seem to exclude a lot of folks. Back in July a drunk tourist waded into the lagoon to pee and lost an arm. In 2015 a man, also intoxicated, was pulled under and killed. His body was found floating the next day. This is why it’s an extremely bad idea to feed crocodiles, which is commonly done around here for the amusement of the tourists. It’s a bad idea because it teaches the crocodiles that (a) people are no threat, and (b) people mean food, and those are two thoughts you don’t want rubbing together in the cerebral cortex of a crocodile.

But it’s important to keep these things in perspective. By far the animal that causes the most human deaths on this planet is the mosquito.

And it is followed as a close second by our own sweet selves.

Now you know.

Copyright © 2017 Randy Fry
By | 2017-12-09T07:43:58+00:00 September 19th, 2017|Uncategorized|16 Comments

The Great Pacific Garbage Patch

Above the tropical north Pacific waters, over a thousand miles west and a little north of the Hawaiian Island chain, a laysan albatross (Phoebastria immutabilis) wheels in the wind.  She is a large and beautiful bird, almost three feet from beak to tail, but with an especially breathtaking wingspan of over twice that.  In the air she is poetry, using a flight technique called dynamic soaring, taking advantage of different wind speeds and directions at different altitudes to get where she needs to go with hardly a wing beat.  This bird is pelagic, meaning ocean-going.  She has a desalinator on board, and the only thing she needs a coastline for is her annual breeding cycle—but then that’s why she’s out here today.  She left a mate and a chick in a nest back on Midway Island nine days ago, and they are waiting for her to return with food.  She forages mostly at night, sitting on the surface and snagging anything that comes by.  She is not discriminating in what she grabs.  She needs anything she can get, and after all, out here, thousands of miles from land, there are only two types of substances on the surface: there is water, and there is food.  She eats squid, crustaceans, fish and carrion, digesting them in her stomach into a high-nutrition oil for her chick.


Laysan Albatross (Phoebastria immutabilis)
By Narrissa Spies (Own work) CC BY-SA 4.0, via Wikimedia Commons


By the time she shows up again at the nest, she has been gone for 17 days and has traveled to points over 1,600 miles distant, but her mate had complete faith that she would return.  After all, their courtship period was five years long.  That’s what it takes to have this kind of trust.

Her mate is also a female.  This is common among laysan albatrosses, in whom the females can outnumber the males by a third.  They are a same-sex couple committed for life, and their lives may be over sixty years long.  They successfully raise chicks together, fertilized by unfaithful males from nearby nests.

But when this female opens her beak to regurgitate her precious haul down her kid’s gullet, something happens that is getting increasingly common:  Out comes a cascade of bottle caps, picnic forks, cigarette lighters, pull-tabs and unidentifiable multi-colored plastic shards.

The chick gulps them down.

These birds cannot know it, but the waters they forage in are in the middle of a slowly rotating gyre of trash that is bigger than the state of Texas.  It’s called the Great Pacific Garbage Patch.


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GarbagepatchLaysan_albatross_plastic_filled_stomach (1)

Laysan albatross killed by plastics
By Claire Fackler [Public domain], via Wikimedia Commons


Probably you’ve heard of it.  And probably, like me, you’ve had a few misconceptions about it.  First of all, it is not a “patch” in the sense of a dense, visible layer of garbage.  It doesn’t look like a landfill.  Actually, if you’re not paying close attention you can sail a boat through it without noticing it.  A racing boat captain (and now conservationist and oceanographer) named Charles Moore was observant enough to notice it in 1997 when returning from Hawaii after the Transpac sailing race.

Some of the litter is large, like laundry baskets and flip-flops, but most of the items are small, unidentifiable chips and fragments.  They are mostly in the top four feet of water, and they’re not obvious, but if you pull a plankton net through the area you get six times more plastic than plankton.  The size of the patch is also very open to interpretation.  You usually hear it compared to the state of Texas (poor Texas always gets these analogies), but it depends on how you draw the line around it, and it also changes and moves around constantly with the winds and currents.  Ocean gyre expert Curtis Ebbesmeyer says that the patches drift and lurch “like a large animal with no leash,” and when one hits an island, it “barfs” its garbage all over the beaches.

A second misconception is that, I’m very sad to tell you, this is not the only garbage patch.  It’s not even the only garbage patch in the North Pacific.  There’s another one straight across the water from it, off the coast of Japan.  There are five in all, slowly rotating in the world’s major ocean gyres.


East and West Pacific Garbage Patches
By NOAA [Public domain] via Wikimedia Commons


The size of the patch is not surprising when  you consider the sheer volume of the plastics we discard.  The L.A. Times estimates that the Los Angeles River alone washes enough plastics out of its mouth each year to fill the Rose Bowl two stories high.  There are probably over seven million tons of plastic in these garbage patches.  Some has been there for decades and decades.  Some has been there since plastic was invented.  Plastic does break down, into water and carbon dioxide, given enough exposure to heat and ultra-violet light.  It’s just that it doesn’t happen in the ocean, or at least it doesn’t happen much, because the water keeps it cool and algae and encrusting organisms shield it from the UV light.  (It also doesn’t happen underground in our landfills.)  So all the plastics gradually concentrate in these gyres, from which there are few exits, and the result is that the first plastic litter ever tossed into the ocean is probably still there.  One piece of plastic (which was pulled from the stomach of a dead albatross) bore a serial number that identified it as a piece of a WWII seaplane that was shot down in 1944.  Ocean current simulators calculate that it spent a decade in the western garbage patch off Japan, then drifted 6,000 miles across the ocean to the eastern garbage patch, where it spent several more decades before getting eaten by an albatross.  Twenty tons of plastic washes up every year on the islands of the Midway Atoll, and five tons of it gets fed to laysan albatross chicks by their parents.  The Midways are their biggest rookery.  Five hundred thousand chicks are born there each year.  Two hundred thousand of them don’t reach adulthood.

Plastic is an accumulator of oily, “hydro-phobic” toxins like DDT and PCBs.  The concentrations of these carcinogens in a piece of free-floating plastic in the ocean can be a million times that of the background sea water.  The plastics are also sponges for “micro-pollutants” like pharmaceuticals, for instance estradiol, which is the chemical used in birth control.  Shellfish like mussels have been observed actually changing sexes.  As the plastic litter breaks down into smaller and smaller pieces, it does not change molecularly—it remains plastic, but it can now enter the food chain through the most efficient and abundant collectors on the planet, which are the filter feeders in the surface waters of the ocean, the zooplankton, which are exactly one level above the very basement of the food pyramid, and from there, these chemicals and pollutants magnify further as they ascend the entire food chain and end up on our seafood menus.  When they break down even further to the sub-one-millimeter size, almost the molecular level, they are still plastic molecules, but are now capable of being absorbed directly into a cell, and what that will end up meaning no one really knows.


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So I know that I have just depressed you and put you in a state of complete despair about the planet we are leaving to our descendants, but believe it or not, I’m about to give you some good news.  And it’s not banal, greenwash good news, either—I’m not going to tell you that carrying your recycling to the curb will solve this problem (it won’t).  No, this good news is real.  The good news is our children.  The good news is that there are kids like Boyan Slat on the planet.


Boyan Slat
Courtesy of The Ocean Cleanup


Boyan Slat was a Dutch high school kid returning from a diving vacation off Greece several years ago in 2011, thoroughly disgusted after seeing more plastics than sea life.  (His diving partner had been enchanted by all the jellyfish.  There were no jellyfish.  They were all plastic bags.)  No sooner did he get back in school than he was asked to do an extra-curricular science project.  Okay, he said.  He knew about the garbage gyres.  He’d read that they couldn’t be fixed.  He’d read that they were bigger than the state of Texas.  He’d read that cleaning them up by towing nets behind ships would take approximately 79,000 years.  The consensus was in from the grown-ups who had created the problem:  It couldn’t be fixed.  He launched his science project anyway.

“Human history,” Boyan says (he’s a pretty quotable kid), “is basically a list of things that couldn’t be done, and then were done.”  The first thing he realized is that it’s dumb to talk about towing nets around behind ships when you’re sitting in the middle of the most famously gigantic gyre of moving water on the planet.  It was obvious to him that the thing to do is to anchor something to the bottom and let the currents do the work.  “Why move through the ocean,” he says, “when the ocean can move through you?”

Even the fact that the plastics are sponges for toxins was a problem that he turned on its end.  That’s a good thing, he said.  Hey, sponges are for clean-up.  Remove the plastics from the ocean, and you’ve removed the toxins too.

And he hated that word, “nets.”  Nets have a mesh size.  Nets catch some things and not others.  Nets catch things they shouldn’t.  Nets ensnare “by-catch” and kill huge numbers of marine organisms.  If the plastic trash floats, which it does, then you should only need a fairly shallow boom, impermeable to everything,  to cause the floating trash to accumulate on the surface.  Any organism under its own power would go under the booms.  Plankton, which by definition is not under its own power, would have to be worked with.


Artist’s Impression of Boyan Slat’s Passive Cleanup Array
By Erwin Zwart/The Ocean Cleanup



What he ended up with was a passive system that just sits there, a V-shaped system of booms tethered to the ocean floor, and, at the crux of the V, a solar-powered, automated processing station.  At the processing station there is a slurry pump, along with a centrifugal device which, he had figured out, would separate plankton from plastic, and then a mesh conveyor belt to carry the plastic into a holding chamber for collection.  Because the booms are not being towed around, they could potentially be hundreds of kilometers long—which they would need to be to get the job done.  He confirmed that the plastics collected are recyclable, and ran some numbers on that.  The plastics from all five gyres could bring in $500 million U.S. dollars.  The project stood a good chance of becoming self-sustaining, or even profitable.  He ran more numbers.  He calculated that a 100-kilometer array of booms could clean up half the Great Pacific Garbage Patch in ten years.  He put the idea out on social media.  He gave a TEDx talk.  That created some buzz—and also a lot of scoffing and criticism—but then it all sort of faded.  He put his head back down and refocused on the engineering.  He worked with a professor to develop a list of fifty questions that would have to be answered in order to call the idea feasible.  Answering them would require money.  He didn’t have any of that.  He was a kid in his bedroom with an idea.

Then, quite suddenly—it happened on March 26, 2013—he looked at his personal email and had 1,500 messages in it.  His phone started ringing off the hook.  The next day he had thousands more emails.  He had gone viral.

Seizing the moment, he launched an on-line crowdfunding campaign.  Fifteen days later he had eighty thousand bucks to work with.  Volunteers started flocking to him.  He started a foundation called The Ocean Cleanup, and launched his feasibility study.

Boyan is twenty-two now, and The Ocean Cleanup has 2.2 million dollars from crowdfunding plus some corporate sponsors, and over a hundred volunteers and staff.  They have printed their 523-page feasibility study (between covers of recycled garbage patch plastic).  Last month (June of 2016) they deployed a prototype off  the coast of the Netherlands.  It’s only 100 meters long.  They’re going to learn from it, and use what they learn in a pilot project off the coast of Japan that will be two kilometers long.  They hope to deploy the full-sized 100-kilometer system in the Great Pacific Garbage Patch by 2020.  They still have plenty of critics, people both skeptical of the engineering, and people concerned about the possible environmental consequences.  After all, this would be the largest man-made structure ever deployed on the ocean’s surface.

But Boyan understands that developing something new is an iterative process, and the software engineer in me just loves that he already gets that.  (It took computer programmers about six decades to figure it out.)  Boyan says, “We are testing not to prove ourselves right, but to learn what doesn’t work.”  So he’s out there doing stuff—building something, listening to his critics, testing, and building something else.  Even if The Ocean Cleanup is the most spectacular kind of failure, I will remain humbled by Boyan Slat.


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A week’s worth of plastic trash, before and after our first few lifestyle changes. We’ll get there…


Susan and I are trying to remove plastics from our lives, or at least from our garbage and recycling.  We launched the project after returning from a particularly trashy beach hike somewhere between Akumal and Tulum, here on the Yucatan Peninsula.  I have to admit here, with all due humility, that generally in our marriage, I am the writer and Susan is the doer, so it is she who is the driving force behind this, and you wouldn’t believe how daunting it looks at first—I mean, look around you.  There is just so much plastic in our lives.  In fact, Susan and I probably will not be able to get to one hundred percent.  But we probably have already gotten to sixty or so, and in only a handful of weeks, and that’s remarkable, and worth doing all by itself.  And we’ve gotten there by making changes that are nothing you would call radical.  We’re keeping notes and taking photographs.  But I won’t go into it all here, because I’m trying to talk Susan into launching her own blog of the project.

We’ll keep you posted.



Copyright © 2016 Randy Fry

By | 2017-05-24T00:03:01+00:00 July 24th, 2016|Uncategorized|6 Comments