Blue, Green, and Huge Aquatic Reptiles
My God, it’s been so long since I last wrote a word for this blog. Paraphrasing Alessandro Manzoni, one of the greatest Italian authors of all time, I hope my two readers (at best) will forgive me- if this piece works as it should, you will at least have a reason to.
As unreal as it still sounds to me, it’s been three months since I left Australia to return home on the shores of Lake Garda, where I hadn’t stayed for longer than a month or so since Summer 2015. In this unemployment hiatus until I hopefully return to Brisbane (oh, right- I officially completed my Master’s degree, meaning that I can’t even use the excuse of being a student anymore), I often find myself reminiscing about the best moments I had down under. The second-last week was particularly dense, if not hectic to put it plainly. The pandemic had forced us to entrench ourselves in Brisbane, which for many inevitably implied the end of any travel plans. However, thanks to Australia’s masterful handling of the situation, the spread of the virus was contained well enough to reopen within-state travelling starting mid-June. As soon as I got the news, I grabbed my laptop and booked the first flight I could find. Destination: the Wet Tropics of Queensland.
To give you a bit of context, the Wet Tropics are a UNESCO World Heritage Site cluster of protected areas stretching along the coast of North Queensland, parallel to the arch-famous Great Barrier Reef. Truth be told, the biodiversity up there (well, up from Brisbane at least) is just as rich on land as it is in the ocean: the Wet Tropics harbor the oldest surviving tropical rainforest on the planet, dating back to a staggering 180 million years ago. A major hotspot within the area is the Daintree river, which cuts through the impenetrable forest for 120 km before flowing into the Pacific. Both the reef and the jungle were high on my bucket list from the very moment I received my acceptation letter in June 2019. When my plane landed at Cairns Airport on a cloudy winter afternoon, it all started to feel like reality.
Now, “winter” is a strong word for tropical Queensland- July is supposed to mirror January in the Southern hemisphere, yet temperatures never dropped below 25 degrees during the day (“dry season” is a much better term in this case). Combine this with Cairns being the lovely town that it is, with a laid back vibe and overall joyful atmosphere (at least to a mere tourist like myself), and you get why my little escapade appeared more than promising right from the very start. Energized by this cheerful atmosphere, I checked in at the place I had booked a few days prior and immediately reserved a spot on an excursion to the Great Barrier Reef scheduled for two days later- the earliest available. Here comes the big letdown, though: I had no waterproof camera and was planning to focus on observing marine life rather than chasing fancy shots in any case, so no Little Mermaid-ish seascapes for you to admire unfortunately. What I can swear to all deities known and unknown is that the reef was simply too overwhelmingly beautiful to be real- well worth the infernal boat trip I had thanks to my dear old sea-sickness. The weather was not particularly favorable (those pesky clouds stalked us all the way to the open ocean), but we could see life teeming in every direction even under somewhat reduced visibility.
As much as the reef warmed my heart, I was happy to set foot back on solid land later that day- not exactly a water person, you know. Besides, I had business to do in the lush rainforest of North Queensland. Two species in particular were carved into my mind, animals I had been dreaming to observe in the wild since I first saw them in documentaries and/or books. With the scrub python (Simalia kinghorni), an unfathomably beautiful six-meter long snake whose already mesmerizing livery radiates flashes of amethistine purple under sunlight, luck sadly was not on my side. Make no mistake, scrub pythons are more than common in the Wet Tropics- however, they are primarily nocturnal and mostly active in summer, although they can still be found out and about occasionally in the colder months. After a full day of herping around Mt. Whitfield National Park, I surrendered to the hard truth that it just wasn’t meant to be. One day, jewel of the jungle. One day.
For my second target species, hopes were way higher. The saltwater crocodile (Crocodylus porosus) is a major tourist attraction in the Wet Tropics, with several tours being offered far and wide specifically to see these imposing predators. To make sure I wouldn’t miss out on such an opportunity, I prepared well in advance: about a week before boarding the aircraft, I reached out to David White, a guide with two decades of experience leading crocodile tours along the course of the Daintree river right into the rainforest. Aboard his boat, the Solar Whisper, encountering crocs is virtually a guarantee- so I was told from friends who enthusiastically recommended him over more publicized (and pricy) companies. I was all set up and ready to go- except for a tiny little detail: I had no car. David’s outpost is located near Cape Tribulation, 150 km north of Cairns and well out of reach for any form of public transport. With only two days left in the Wet Tropics, I had no time to spare and was in dire need of help. Thankfully, I was in a great place to find it.
If you are a student on a quest to find something in the tropical belt- be it your greater purpose in life or huge aquatic reptiles- chances are you will end up in a hostel full of people of the same sort (by the way, gentle reminder to please make sure to check your internalized neocolonial mindset before you set off on your adventure). Despite my visceral aversion for overly social environments, I am quite fond of hostels and their melting pot of people who wouldn’t possibly gather in the same place in any other context. The lovely little place I was staying at was no exception- which, according to a staff member who knew about my crocodilian fantasies, was a great resource. Everyone comes here to travel, he said. Just ask around and I’m sure you’ll find someone willing to join you. As it turned out, he was right. Specifically, “someone” came in the shape of Elisa and Marina (Eli and Mari hereafter), two kickass Argentinian young ladies who had left their hometown of Córdoba to pursue the Australian Dream a few months back. Eli in particular was especially afraid of crocodiles, which, for reasons that still elude me, persuaded her to agree with Mari on tagging along the weird reptile nerd and drive all the way to the Daintree with her car. It honestly baffles me how there are still people out there who genuinely believe I know what I’m doing.
Now that everything was in place, I phoned David again to book three places on the Solar Whisper for my last day in Cairns- my flight would leave in the early evening, so time was not an issue. With unbridled enthusiasm- which might have made me appear a tad insane to Eli and Mari, in hindsight- I donned my field clothes and camera and hopped in the car. Time to go. The road itself led us through some of the most beautiful sceneries I have ever seen: lush rainforest on the left, endless ocean on the right just on the edge of the asphalt. After just under two hours, the Daintree finally came in sight, as emerald green as you can imagine, with David’s outpost and the dock where the Solar Whisper was likely anchored when not in service standing where barely any other sign of humanity could be seen. A lovely lady who I presumed to be David’s wife welcomed us just before the boat came back from the previous tour. Our time had come.
Now, spotting animals is as hard a task as they come- and crocodiles are certainly no exception. The lush mangrove cover offered plenty of hides where even the largest croc could lay submerged without anyone noticing, perhaps only keeping its eyes and nostrils on the surface. If you consider that out of around 10 people on the boat, only David (who proved to be as friendly as they come, with a voice that could have come straight out of an audioguide) had proper experience tracking wildlife, you’ll easily understand why everyone fell silent as soon as the boat started moving. All eyes were meticulously scrutinizing every inch of terrain, every log, every maze of mangrove roots. And yet, the first animal we came across was right where none of us but David thought of looking: right over our heads.
I’m still not sure how David managed to detect this common tree snake (Dendrelaphis punctulatus) amidst so many leaves and twigs, especially since its livery was barely any darker than the leaves themselves. Be that as it may, I was still delighted to encounter this animal. The common tree snake is as harmless as they come (plot twist, not everything in Australia is deadly venomous) and highly common along the Eastern coast of Australia, reaching as far south as New South Wales. Nonetheless, it remains one of my favorite Australian snakes thanks to its beautiful coloration (ranging from vibrant green to pitch black through aquamarine) and elegant silhouette- the latter comes in handy for its generally arboreal lifestyle, which requires a slender and light body to cruise swiftly on trunks and branches. A mainly diurnal species, the common tree snake reaches almost two meters in length and can rely on an excellent eyesight that allows it to spot the lizards and amphibians it regularly preys upon. This ecological profile fits many of the Australian colubrids (family Colubridae), lonely representatives of what is arguably the dominant snake family virtually everywhere else in the world. Hell, the very genus Dendrelaphis itself comprises as many as 40 species found from India to Papua New Guinea, yet only two of them- our friend and the smaller Northern tree snake (Dendrelaphis calligaster)– have made their way into Australia. As I explained in previous posts, the reason fo such a paucity of colubrids in the land down under (only 9 species in total) is likely the late arrival of these snakes compared to pythons and elapids, which instead found the entire continent up for the taking and radiated explosively to fill nearly all available ecological niches. In fact, it is no coincidence that all but one of the Australian colubrids are either arboreal or aquatic- adaptations they had already evolved prior to their dispersal into the country, which gave them a great advantage over other colubrids that would have found themselves unable to overcome competition from a wealth of elapids and/or pythons with terrestrial or fossorial habits. When in Rome… Do what the Romans haven’t already done.
As much as I would have loved to wait for our serpentine friend to move and show off its beautiful colors, the Solar Whisper was on a tight schedule. Luckily, the Daintree rainforest has many tricks up its canopy when it comes to wildlife.
Look closely. There’s three of them. Once you see them, you won’t be able to unsee them anymore. This is a happy family of Papuan frogmouths (Podargus papuensis), a bird native to New Guinea and North Queensland that might well remind you of an owl but actually belongs to a completely different order- quite frankly, this applies to countless Australian species that look an awful lot like Old World animals and yet have little to do with them if anything at all. Frogmouths specifically are part of the family Podargidae, which has its largest representative in the Papuan frogmouth itself. To be fair, these quirky birds do share certain physical and behavioral traits with owls: they are nocturnal and have particularly large eyes to assist them in nighttime- in fact, the three in the picture (likely a pair with their offspring) were sleeping on the branch they regularly perch on according to David’s recount. Their perfectly camouflaged plumage helps them elude diurnal predators when resting, which works just as great with photo-hungry tourists. Oh, how silly of me to forget- their name comes from the humongous gape of their beak when they open it, which resembles the mouth of a frog in that sense. However, no need to worry: frogmouths are generally insectivorous. Sure, they will also take the occasional small vertebrate every now and again, but pose no danger whatsoever to humans- the only way a frogmouth could kill you is via cuteness overdose.
After a delighful snake and bird appetizer, we were more than ready for the crocodile main course- all metaphors people, rest assured that not a single animal was harmed for the sake of this blog post. Lucky as we were that day, a crocodile did show up right after we left the frogmouths behind. If you’re picturing a monstrous behemoth thundering its way through the water, you’re in for a big surprise.
Talking about cuteness overload, just look at this little goofball of a baby saltie (yes, that’s how they call saltwater crocodiles in Australia) we found basking on a floating log. That tiny snout made us all melt, as if we had a cute puppy before us. However, life for a neonate crocodile is most often nothing short of hell on Earth. At this age, they are vunerable to a myriad of predators down there in Australia- other crocodiles, birds, fishes (including sharks), monitor lizards, snakes, and dingoes, some of which are also habitual nest raiders that gladly feast on crocodile eggs. Like most extant crocodilians, the saltwater crocodile displays maternal care, with mothers often defending their offspring as best they can at least in the first days/weeks after hatching (this individual, however, was alone). Still, mortality remains high: it is estimated that only 54% of a given clutch of salties will live to celebrate their first birthday- and for crocodilian standards, that’s quite a big number. To make up for this, neonate saltwater crocodiles have to grow a lot, and quickly- which they happen to be great at. In fact, juvenile salties have a remarkably high food conversion rate (i.e. the ability to convert food into biomass), which results in growth rates of about 0.15 mm per day. No wonder, then, that 30-cm long babies like this one stretch past 1 m by the time they turn one year old. When they reach around 1.5 m, the world turns upside down for them. No more hiding, no more watching every step- in Australia, an adult saltwater crocodile has no predators except for large sharks (likely mutual predation), even larger conspecifics, and (of course) humans. That is the kind of saltie Eli was so afraid of- and the Daintree promptly handed her an opportunity to face her demons.
Just as we turned past a bend of the river, the unmistakable silhouette of this stunning female crocodile appeared in the distance. There she lay, over 3 m in length, completely unfazed by our presence even when the boat got literally at a few meters’ distance. How do I know she was a female? Oh, I wouldn’t have been able to tell at first sight- David, however, knew that and much more. You see, his knowledge of this patch of land (and water) is so deep that he learned to recognize every single adult crocodile in the area at a glance- and that’s not all. He named these animals too, and loves to recount their everyday life in delightfully funny stories he posts on his Facebook page under the title Days of the Daintree– much like a reptilian version of Beautiful, I dare say. This lovely lady here is Lizzie, one of the main characters in the show. She was casually resting on the river bank with her right hind leg still submerged, which amused Eli and Mari greatly- if we were to stick to the celebrity vibe, Marilyn Monroe’s swimming pool scene in Something’s Got To Give or Ursula Andress’s iconic emergence from the sea in Dr. No would likely would probably come to mind.
Since Lizzie was kind enough to show herself on land from head to tail, we can use her as a template to address some key features of crocodilian anatomy. Let’s start from the tail itself: dragon-like in appearance, that’s where the real muscle power is- crocodilians use it to propel themselves in water and launch themselves in bursts of amazing speed when hunting or escaping from a threat. When it comes to long-distance movements, these animals are capable of surprisingly long voyages and possess an incredible homing ability- emblematic is the case of a male saltie that was translocated 411 km of coastline away from his territory and yet managed to travel all the way back in under a month. In your face, Captain Cook.
Moving along Lizzie’s spine, we have the trademark armored scutes, aptly named osteoderms (“bony skin”) to reflect the fact that they are more or less heavily ossified. Osteoderms protrude throughout the entire length of the body, but there is great interspecific variation in how heavy this natural armor is. In fact, huge species like the saltwater crocodile itself, the American crocodile (Crocodylus acutus) and the Nile crocodile (Crocodylus niloticus) generally have a much more scattered and punctuated osteoderm cover compared to the panzer-like pattern found in smaller (and therefore more vulnerable to predation) species such as the African dwarf crocodiles (genus Osteolaemus). Then, of course, there is the mouth. Those teeth you see there are ideal to ensure a tight grip on even the most slippery prey, while the sheer crushing power of the jaw arguably equips large crocodilians with a tremendous bite force, arguably the strongest among all living animals.
With all this in mind, it goes without saying that Lizzie is a truly impressive creature. Yet, she’s not even close to the largest size a saltwater crocodile can attain- as in nearly all crocodilians, female salties are significantly smaller than males. In fact, usually a large male will set aside a large swathe of territory for himself and multiple females to mate with, patrolling and defending it against rival males intent on replacing him. So, if Lizzie was but one of several ladies, who was the “main man” in the yard? As it turned out, it would take us only a couple of minutes after leaving Lizzie behind to meet him. The king of the Daintree, his unconventional lover, and so much more will feature in Part 2 of this piece- coming next week. In the meantime, stay tuned: believe me, you do not want to miss it.