TOP OF THE CROCODILE POPS
Not only do India’s fish-eating gharials look strange, they make unusually attentive mums and dads. These reptiles are among the best in the world, says Janaki Lenin.
February fog blankets the wide River Chambal in northern India and shrouds from view the settlements along its banks. A new tension fills the air. Until now, one particularly impressive scarred 5m-long male gharial, sporting a magnificent bulbous lump called a ghara on the end of his long snout, has been civil. He has been lazing alongside his fellow gharials as their dark hides soak up the rays. But now, suddenly, he can’t bear the sight of another big male.
The rival reptiles rise out of the water with their snouts in the air, sizing each other up. They nip one another, taking the skin off the slender jaws. Blood oozes from puncture wounds in the ghara; the delicate snouts of gharials can’t withstand violent ramming. When neither animal backs off, the contest progresses to a wrestling match. The mighty combatants jostle for hours until one succeeds in mounting the other.
The defeated rival surges forwards in a serpentine movement, possibly to shake the other off his back. He concedes this round and watches the victor patrol his fiefdom. Snorting noisily, the dominant individual shows off his size by arching his back and his tail’s serrated horny plates, called scutes, above the water. The trounced male tests his mettle again and again over the next few
days, until he finally realises that he cannot unseat the winner and gives up.
Female gharials watch the outcome of the titanic battle with keen interest, because the victorious male will father their offspring. But Jeffrey Lang, a retired professor of biology from the University of North Dakota, says it’s not so simple. Some females may not settle for just one mate, instead travelling along the river to visit other dominant males. In 2008 Lang founded the Gharial Ecology Project after a mysterious die-off the previous winter, when more than 100 gharials were found floating lifeless in the Chambal River.
UNCERTAIN FUTURE
When vets cut through the cadavers, they saw uric acid crystals caked on the internal organs and solidified in the joints. Gout. Their kidneys had failed. Some toxin had killed gharials of a particular size: 2–4m in length. Mugger crocodiles, turtles, Ganges river dolphins, fish and waterbirds escaped its clutches. It didn’t even affect small gharials or the big adults. In 2006, experts had declared that only 200 adult gharials survived in India and Nepal, so the catastrophe had severe implications for the species’ future.
Despite being a tributary of the holy but polluted Ganges, the Chambal is a relatively clean river. How were the gharials poisoned then? Suspicion pointed to the Yamuna River, which drains industrial effluents and sewerage from cities like Delhi and Agra. Did gharials of the Chambal swim 50–60km downriver to the septic Yamuna? No one knew.
By setting up the Gharial Ecology Project, Lang hoped to find out. One of its key aims is to understand how gharials use rivers. It is supported by international zoos through the Madras Crocodile Bank Trust, an Indian reptile and amphibian conservation organisation, and over the past decade has attached radio and GPS transmitters to more than 50 gharials and installed trail cameras at nesting sites to study their behaviour. Lang’s main finding: these animals are unlike any other crocodilian in the world.
As spring lifts the low-lying mist from the Chambal, flocks of winter migrants – bar-headed geese and Brahminy ducks – take to the skies heading for their summer homes. And egg-heavy female gharials labour up steep sandbanks to dig nests under the cover of darkness. Their stubby legs barely support their weight. Females of most other crocodilian species put distance between each other. But gharials do it differently. Each nest is no more than a gharial body-length or two away, and as many as 20 or 30 females may share a sandbank, often the same one year after year.
Lang has observed the females don’t make nests at the very top of a sandbank but about two-thirds of the way up. This strategy makes it difficult for predators such as jackals and hyenas to reach them. Gharial eggs, as big as geese eggs, are the largest of any crocodilians. An average clutch has between 35 and 50 – a feast for any egg thief that manages to dig its way into a nest. But the predator has to bolt as many as it can, for the mother gharials aren’t far away. They lie soaking in the deep waters below the sandbank, keeping an eye out for prying claws.
Although they have sharp teeth and could seriously injure their enemies, gharials do not eat them. Their teeth have custom-evolved to grab slippery fish. Despite their enormous size, these reptiles have no gastronomic interest in birds or mammals (including humans), alive or dead. No other big crocodilian eschews mammalian flesh to this degree.
With their mothers keeping the sandbanks clear of intruders for two months, the embryos develop in the underground incubation chambers. As spring gives way to summer, the heat builds up. The sand temperature assigns the sex of the hatchlings, since crocodilians have no sex chromosomes. At the height of summer, when daytime temperatures touch an infernal 45–50ºC, the young are ready to hatch. They can’t dig themselves out of the 45cm-deep hole, though. From inside their eggs they call for help – sounds the expectant mothers have been waiting to hear. How each mother knows where her nest is located remains a mystery.
WARM WELCOME
After nightfall, the devoted mothers heave themselves out of the water once again. In the heat the river has receded farther from the bank, yet they hike up the towering sandbanks – almost in unison, since all the nests hatch simultaneously. In other crocodilian species, the mothers help their babies hatch by rolling the eggs in their mouths and squeezing gently. The long narrow gharial snout doesn’t allow this. So the females simply open the nest and let the young hatch on their own.
The freed hatchlings scurry and slide to the water to their
DESPITE THEIR ENORMOUS SIZE, GHARIALS HAVE NO INTEREST IN EATING BIRDS OR MAMMALS. THEIR TEETH HAVE EVOLVED TO GRAB SLIPPERY FISH.
dad, and by dawn hundreds of them are floating in a crèche near the shore. A couple of dominant mothers take turns protecting all the hatchlings – their own and other females’ offspring. If the adults had been watchful earlier, now their protectiveness reaches exaggerated proportions. They have reason to worry.
Throughout the day, the crèche attracts predatory eyes. River terns and Pallas’s fish eagles perform aerial raids, swooping down to snatch one helpless hatchling at a time. The guarding females have to be ever vigilant, leaping and snapping their jaws to keep these birds at bay. They’re especially wary of woolly-necked storks, the main devourer of their young. They can’t relax even after dark, when golden jackals and striped hyenas are on the prowl.
EASY PICKINGS
Occasionally, young 3m-long male gharials, on the threshold of adulthood, sneak in and take any unhealthy or weak stragglers. The females chase them away before they can do any further damage. Cannibalism of young is well-known among crocodilians; this hot time of year hasn’t much prey to offer. “There’s tremendous pressure on the smaller growing males to reach peak condition, which may drive this behaviour,” says Lang.
Childcare is not the sole preserve of a few females. At each colony, a ghara- sporting single male assumes the role of crèche guardian, working in tandem with the attentive females to protect the vulnerable hatchlings. He positions himself between any intruder and the crèche, hissing loudly and inflating his body to show off his size.
The large male may be feisty, but he’s one of the most attentive fathers in the animal kingdom. When the coast is clear, he offers his head and back as floating platforms for the little ones to rest. But if anything threatens their survival, he’s quick to take action, unceremoniously dumping the hatchlings in the water. This superdad is a full-time bodyguard. Yet often he may not even be the father of the offspring he defends with such devotion.
“I don’t call this parenting anymore, because the guarding male may not be a parent,” Lang says. He has recorded a young male assume superdad duties for two consecutive years. This particular male definitely did not court or mate in those years. In 2017, he became the dominant breeding male in the same area he had guarded in previous years. But then he was the sole guardian of a crèche that included many of his own offspring.
“Maybe he was apprenticing,” Lang speculates. “Males and females communicate in some manner during
AT EACH COLONY, A SINGLE MALE ASSUMES THE ROLE OF CRÈCHE GUARDIAN AND PROTECTS THE VULNERABLE YOUNG.
protection. They work together when multiple predators approach the hatchlings. These younger apprentice males may become familiar with nesting females, giving them an advantage in future breeding attempts.”
On another occasion, an adult male gharial chased away one of the superdads and guarded his rival’s brood. He may do this to “maintain his dominance as a breeder”, says Lang.
LEFT BEHIND
The behaviour, unique among crocodilians, lasts a few weeks until the monsoon reaches full swing in July or August. Then the situation changes completely.
At that point the adults abandon the young and head downriver. They swim many kilometres in a matter of days to reach the confluence of the Chambal and Yamuna. One female with a GPS transmitter coasted more than 200km downstream in less than a week. Meanwhile, the young scatter. “When the water comes up it creates a lot of shallow habitat for the hatchlings,” explains Lang. “The crèche loses its integrity when the adults are no longer nearby.”
The turbulence of the waters at the Chambal–Yamuna junction is a rich fishing spot. Here, the adult gharials do nothing but gorge on fish for the next two months. “They seem to get as much as two-thirds to three-quarters of their energy requirements during the warm monsoon months, when water temperatures are high and food is abundant,” says Lang.
HANGING AROUND
However, the half-grown and subadult gharials don’t budge, staying year-round in the Chambal. This is one reason the poisoned victims couldn’t have died from toxins in the Yamuna in the winter of 2007. Instead, a one-time toxic event in the local area probably killed them. The mystery hasn’t been solved. But Lang’s research is nonetheless revealing much that was unknown about this species.
In the decade since, gharials are faring better than they were. Lang conservatively estimates the total adult gharial population at between 650 and 750. The bulk of these animals, about 80 per cent, live in the 428km-long National Chambal Wildlife Sanctuary.
“The Chambal is the crown jewel in terms of the remaining wild gharials, living in an open, dynamic big river,” says Lang.
When the monsoon recedes in September the adult gharials, with their bellies full of fish, glide upriver back to their old haunts. Very few of their hatchlings will have survived in their absence. But, come February, there will be plenty of opportunity to have a go at it again.