It was 10 years ago when I first saw a croc in Parliament Lake. My five-year-old son and I, pedalling our bikes along the exercise track opposite Parliament, noticed it just a few metres from shore facing our way. Nate said ‘whoa!’ as we braked to a halt. With snout and eyes clearly visible above the water, it peered at my little boy with malevolent ideation.
I’ve glimpsed crocs in and around the lake several times since then: one time, a huge one, jaws agape, basking at the edge of a large island; another time, a top jaw slanting out of the water’s edge a few dozen meters from the deck where I sipped coffee outside Bakery at the Lake. Slowly, the jaw went down and disappeared.
This past December, while driving down Japan Friendship Road, we spied a little crowd by the lakeside, phone cameras up. Our trusty tuk driver Ajith pulled quickly to the curb. The rear two thirds of a massive croc splayed on a small tree-topped island just out from shore, its head hidden by underbrush. I estimate its length at maybe four metres, which would make it an adult male saltwater croc.
On a day in January, we again saw a saltie, probably the same one, on the same little island. Ajith wheeled over. No one else was there this time. Nate grabbed my phone and snapped a great pic. This time its head, clearly visible, lay jaws agape facing the lake.
Everyone’s heard the legend that President Chandrika Kumaratunga stocked crocs in the lake to keep terrorists from swimming out to Parliament. Another version holds that she inadvertently created a croc-friendly habitat with engineering projects like the Water’s Edge complex. The truth of course is that croc presence in the lake requires no human agency. Crocs got here long ago, probably before people.
Even before anyone built canals connecting Kotte with the sea, crocs prowled the marshes in between. Marshland extended into the area now occupied by Parliament Lake. It remains possible, however, that recent canal upgrades to improve drainage has helped salties move to the suburbs.
Another bit of lore concerns the Dutch stocking crocs in today’s Beira Lake to keep slaves from attempting escape by water from nighttime quarters on Slave Island. This tale also sounds like a crock (Sorry!). It gets repeated in journalistic history pieces without documentation on the alleged practice. We can wonder why the Dutch would bother stocking a water body already quite croc-friendly.
Experts confirm that salties predominate in Colomboland’s waterways, pushing its smaller cousin mugger croc to the margins. Local saltie numbers may be on the rise, even if Lanka’s overall population lies under threat. My golf-playing friend Gayan reports frequent sightings at the Club.
Salties withstand prolonged exposure in saline ocean water, but that is not their exclusive or even favourite habitat. They thrive in brackish lagoons and river mouths. They seek low-saline water for breeding. Their hatchlings may best enjoy low-salt waterways, which means that Parliament Lake might be prime breeding and nursing territory. It also means that salties probably evolved away from mainly freshwater habitat towards stronger seawater tolerance.
Each other’s closest relatives, salties and muggers diverged from a common ancestor between four and nine million years ago (mya), with salties starting their journey into enhanced saline tolerance. But the saltie/mugger common ancestor already possessed a bit of that tolerance. It achieved this through special glands under its tongue for excreting salt. Muggers retain this gland, which allows brief stints at sea. With intensification of this nifty apparatus, salties can ingest seawater while hunting without harm from over-salination.
Muggers and salties could both bid for Top Reptilian Mommy. Like birds, they build nests from mud and vegetation. They guard eggs for many weeks from hungry monitor lizards, snakes, jackals, birds, and other crocs. In their eggs, infants start chirping, telling Mommy it’s time to dig them out.
She will roll shells gently around her mouth to help them perforate safely. Then she will tuck hatchlings in her mouth a few at a time and carry them to a spot of water where they can remain as safe as possible. She spends months protecting them from predators, responding to distress calls and feeding them when they can’t catch enough bugs, minnows, and tadpoles on their own. For all this care, precious few hatchlings survive to maturity.
Salties inhabit a huge oceanic range stretching from the Philippines, New Guinea, and Australia across southeast Asia to the Indian subcontinent. Sri Lanka lies at the western edge of their range. Muggers command a smaller range, limited to the greater Indian subcontinent from eastern Iran to eastern India. They once reached farther east but have fallen extinct in Bangladesh and Myanmar.
Working sea, lagoons, and rivers, salties prevail along Lanka’s southern and western ‘wet zone’ coasts. Muggers cozy up mainly in the dry zone, finding their sweet spot especially in the numerous tanks dotting Lanka’s landscape even far inland. Those ancient irrigation tanks give muggers a higher density in Sri Lanka than anywhere else.
Scientists have only recently fathomed how and why salties acquired their huge range. Giant saltie size lies in males, not females. Males reach lengths of 20 feet and weights of 1,000 kilograms, while females rarely exceed 10 feet and 200 kilograms. Male size differential over females (‘sexual dimorphism’) goes hand in hand with fierce male territoriality for hunting ground, basking spots and control of females. Violent clashes among males cause serious injury and death.
Dominant males often direct their ire at juveniles, potential future competitors in their territories. Grown females do likewise for nesting grounds. Both sexes eat juveniles with no inhibition. After tenderly raising the little cuties, Mommy may later see them as lunch.
Faced with all this, juvies often migrate to survive. They take to the sea and swim or drift with tides and currents to distant locations, hopefully thin on grown-ups, so as to have their own chance of reaching maturity. For that matter, even full-grown salties migrate away from croc crowds to stake out fresh territory.
Low ice age sea levels made migration easier back in the day than it is today. Migrants now tolerate long months at sea without food, aided by super-slow metabolism. Oxygen consumption and heart rates drop. Like whales and dolphins, salties can sleep one half-brain at a time so as to remain responsive to changing conditions while catching needed shuteye. Satellite tracking reveals journeys covering hundreds of kilometers to final landfall. Females isolate sperm in preservative tubules, then self-fertilise their eggs upon finding good nesting grounds.
Saltie’s success is owed to some stunning additional physiological adaptation, besides what’s easily noticed. His close-set eyes give him excellent binocular vision, crucial for judging distance rightly. He carries a strong antibiotic called ‘crocodillin,’ which helps heal wounds and resist infection even in highly septic habitats. Elastic lungs can hold huge amounts of air. Special blood chemistry and slow heartbeat in water help him deliver nearly all his inhaled oxygen to cells, where humans manage only about one third.
Equally impressive is his prowess in extracting oxygen from what he inhales. Our mammal breathing is ‘tidal’. Inhalation and exhalation go back and forth through the same pathway, so that some recently inhaled high-oxygen air gets exhaled back out with depleted air. Like birds, by contrast, crocs feature ‘unidirectional’ airflow around a ‘loop,’ facilitating maximum oxygen extraction before exiting. Dinosaurs had it too, with birds inheriting it directly.
Fresh inhaled airflow divides, some channelled directly to lungs and some to a holding chamber below or behind the lungs. Oxygen arriving directly in the lungs passes quickly into blood. With exhalation, holding chamber air gets pushed forward into lungs for oxygen extraction, while stale air lingering in lungs gets pushed forward for expulsion. Oxygen extraction in the lungs takes place continuously through both inhalation and exhalation. Science has only recently learned that monitor lizards share this remarkable feature. Despite lifestyle resemblances, crocs and monitors are but distant cousins. ‘Convergent evolution,’ anyone?
Like birds and mammals, crocodilians also sport four-chamber hearts that keep oxygenated blood flowing in from lungs separate from stale blood returning from the working body. In most other reptiles, three-chamber hearts mix oxygenated and depleted blood in a single ventricle and thereby fail to maximise oxygen supply pumped out to muscles and brains.
Amazingly enough, monitor lizards share such four-chamber hearts also. Some dinosaurs may have had them as well. Four-chamber hearts do not automatically produce warm blood, but warm blood cannot happen without them.
The ‘crocodilian’ cluster includes ‘true crocs’ like salties and muggers, along with alligators, caymans and gharials. Crocodilians lie closer in lineage to birds than to other reptiles like turtles, snakes and lizards.
Birds and crocodilians both stem from a larger cluster called ‘archosaurs,’ also including dinosaurs and pterosaurs which both fell extinct in the cataclysm 65-66 mya, leaving birds and crocodilians to carry their legacy forward. Their similar nesting and prolonged nursing behaviours testify to ancient sisterhood.
What’s with those gaping jaws? Besides intimidating critters who might think to mess with him while he’s dozing, this serves a vital physiological function. Cold-blooded — unlike birds — he basks to warm his blood for strenuous activity (birds, being warm-blooded, routinely fly of course and practice other energetic behaviour). Danger in crocodile basking to get warm blood lies in potentially overheated brains, with serious and possibly fatal consequences. Air moving through his mouth cools blood lying close to the surface, thereby keeping his brain on chill. Like salties and for the same reasons, muggers also bask and gape simultaneously. The same goes for other crocodilians.
Today’s crocodilians fit within a larger ancient cluster, itself within the archosaur cluster, called ‘crocodylomorphs’ (similar to crocodiles). All its living and extinct members represent the same basic body plan, but with substantial variations, as will soon become clear.
It’s easy to grasp why scientists call our living crocodilians ‘semiaquatic’: they are comfortable with both water (hunting) and land (basking and nesting). Some of their extinct relatives, however, operated exclusively on land, while others functioned exclusively at sea. These clusters flourished at various times and places since the pre-dinosaur origin of the crocodile lineage some 250 mya. Science has identified nearly 600 extinct crocodylomorph genuses (OK, ‘genera’). On land, they included not only carnivores but also omnivores, insectivores, and herbivores.
Among the earliest crocodylomorphs, land-going bipeds prevailed. In what is now North America 230 mya, ‘Carnufex carolinensis’ walked and ran exclusively on hind limbs and played top predator at nine feet long. At maybe 220 mya, lanky ‘Saltoposuchus’ reached four or five feet in length and 15 kilograms in weight. It ran quickly on long hind legs, snatching small lizards, insects, and early mammals with slender pointed teeth. At around 200 mya, ‘Postosuchus’ preyed on early dinosaurs with a massive skull and dagger-like dentition.
Bipedal crocodylomorphs declined after that as bipedal dinosaurs like the giant ‘Allosaurus’ took the stage. We can’t know for sure whether they disappeared entirely for a time. At 115 mya, however, biped crocodylomorph ‘Batrachopus grandis’ left footprints which later fossilised in what is now South Korea. Known only from those prints, it stood three or four meters in length.
Unlike bipeds, which may have emerged and fallen extinct separately from one another, fully sea-going crocodylomorphs saw one unified and extended run. ‘Metriorhynchids’ emerged around 170 mya and met their final demise probably somewhere around 100 mya. They clustered in perhaps as many as 20 distinct genera.
Some functioned as apex predators. They shared small paddle-like forelimbs, precluding movement on land, and smooth scaleless skin. Long and tubular for efficient swimming, they used shark-like vertical tail flukes for propulsion. A wide hip gap indicates birthing live babies at sea. Their enlarged salt-excretion glands need no explanation.
We can distinguish two types of extinction: ‘cataclysmic,’ with mass worldwide die-offs like the dinosaur catastrophe, and ‘retail,’ where a certain animal type cannot survive fluctuations in its environment and habitat. Darwin wrote plenty about retail extinctions in ‘On the Origin of Species’, emphasising how they open room for the emergence of new and better-adapted types. He dismissed mass extinctions as implausible, doubting that conditions on Earth could change drastically over short time periods.
That was before we knew about projectiles hurtling thousands of miles per second into Earth, triggering relentless wildfires, glass-particle rain, colossal tsunamis and other unpleasantness, nor about continent-size volcanic eruptions lasting a million years or so, spewing debris, poison gases and CO2 that blocked the sun (global cooling), blanketed the globe (warming) and turned seas to de-oxygenated acid. Some crocodylomorphs, today’s crocodilians, somehow made it through all this.
In any case, the metriorhynchid extinction was the retail variety. Like most retail extinctions, it came gradually like bankruptcy, until like bankruptcy it came all at once. Typical of retail extinctions, it also came, like bankruptcy, multi-causally: climate change, fluctuating sea levels and temperatures, vagaries of prey species and competition with other seagoing predators. Rivals included sharks, ichthyosaurs, pliosaurs, plesiosaurs, and maybe even those seaborne and sea-born mosasaurs: massive, monstrous Mesozoic monitors.
Conservation outlooks for salties and muggers in Sri Lanka run contrary to world outlooks. Salties receive a grade of ‘least concern’ from the International Union for the Conservation of Nature (IUCN). Worldwide, they’re doing just fine, as Australia can attest. In Sri Lanka, however, their habitat intersects a lot with prime coastal real estate. Salties rate as ‘endangered’ under Lanka’s national conservation index. Only some 300 adults may remain, sharply down from a century ago, so say the experts. Shrinking seaside habitat may drive salties increasingly towards inland spots…like Parliament Lake.
Muggers, meanwhile, rate as ‘vulnerable’ under IUCN classification. Numbers went plummeting in India over recent decades as rising rural populations munched away at mugger ranges. World numbers now may lie below 10,000. But numbers remain substantial in Sri Lanka (around 3,000) and may even be rising, thanks in part to those ancient tanks. More good news lies in declining human population pressure as rural Lankans move increasingly townward.
We should shun complacency of course. Salties and muggers both rightly claim protection under our Fauna and Flora Protection Ordinance. Meanwhile, however, and on the other hand, someone should be thinking about possible blowback from protection. In the US, protected deer, coyotes, and mountain lions cause problems. What if our local salties start roaming farther afield?
Author, lawyer, and ex-professor, Mark Hager lives in Pelawatte with his family.
Further Reading:
Kelly, Crocodile: Evolution’s Greatest Survivor
De Silva, The Crocodiles of Sri Lanka
Daniel, ‘Urban Crocodiles: Should We Be Worried?’ (Roar Media, April 27, 2018)
Rodrigo, ‘Colombo’s Seagoing Crocodiles Under Pressure After Diver’s Killing’ (Monga Bay, Jan. 26, 2022)
Amarasinghe, ‘Human-Crocodile Conflict and Conservation Implications of Saltwater Crocodiles in Sri
Lanka (Journal of Threatened Taxa, 7(5): 7111–7130, 2015)