WILD LIFE | 06.05.18
Basking on the Brink
An "unholy" river in India may be the last, best hope for one of the world's largest and most imperiled crocodilians.
At the time, there were thought to be just 200 to 250 breeding-age gharials (Gavialis gangeticus
) left in the world. And while only a dozen or so of the victims had reached reproductive age, many were close. A loss of more than 100 of them represented a major blow for a population already in crisis. Having been classified by the International Union for Conservation of Nature (IUCN) as critically endangered even before the die-off began, the species was clearly in trouble—including here on the Chambal, its last remaining stronghold.
“We opened a Pandora’s box. There was all this stuff we didn’t know,” says Lang, now a scientific advisor for the Madras Crocodile Bank Trust and the Gharial Conservation Alliance. To help fill the many knowledge gaps surrounding these imperiled creatures, Lang—along with conservationist Rom Whitaker and croc researcher Dhruvajyoti Basu—launched a research project on the Chambal that would reveal many new details about basic gharial natural history and ecology, from their movements and breeding behaviors to the many threats they face over the course of their lives.
Even as the mystery lingered over the 2008 die-off, study results began to provide clues about how best to protect the gharial—both from the potential for similar catastrophes and from the growing pressure of development that threatens the species’ very existence.
Chambal River, India
According to ancient Indian legend, thousands of cows were once slaughtered along the banks of the Chambal, causing the river to run red with blood. Because of this, unlike other major rivers in India, the Chambal has long been considered unholy. That belief has deterred development along the river and left the ecosystem here relatively pristine. Few roads lead to the water and few bridges cross it, despite the fact that it flows through one of the most densely populated regions of the world. What’s more, since 1979, more than two-thirds of the river has been designated a sanctuary to protect South Asian river dolphins (Platanista gangetica), red-crowned roofed turtles (Batagur kachuga), gharials, and other wildlife that nest along its wide, sandy banks during the dry season.
“The Chambal is a uniquely stark and dangerous-looking landscape, especially if you know the history,” Whitaker says. “Walking through the tall ravines is a bit like traversing a miniature Grand Canyon, with a bit of an extra edge knowing you are in leopard, cobra, and viper country.”
The creature’s most peculiar feature is the male gharial’s ghara—a spherical and flexible lump of cartilage near the end of its snout that grows as an extension of the nasal chamber after males reach a length of 4.5 meters (14 feet) or so. Researchers don’t yet know what function the ghara serves, but one theory is that it somehow helps to amplify hissing and underwater popping sounds that, according to recent research, help males establish and maintain breeding territories and entice females into courtship.
“If the species is going to survive, it’s going to survive in the Chambal.”
—Jeffrey Lang, Gharial Conservation Alliance
Results have provided a variety of basic information about the species—much of it carrying conservation implications. Mid-sized gharials (which were, strangely, the only ones affected by the die-off), for example, rarely travel more than 20 to 30 kilometers (12 to 18 miles) from their home base, and they usually cover less ground than that. According to Lang, this suggests that the die-off likely resulted from a single, localized toxic source, as opposed to more widespread river pollution.
Other research sparked by the die-off—and funded in large part by the international zoo community—has revealed surprising and elaborate parental-care behaviors among gharials. After hatching on the river’s sandy banks just before the rainy season begins in July, hundreds to more than a thousand little gharials typically gather in one place. Multiple mothers of this mixed brood take turns checking on the hatchlings day and night, protecting the babies from herons and other predators. When dangers mount, a single male may join in on the defense effort. This vigil will last until the young finally disperse as September’s monsoon rains cause the Chambal to swell once again.
While this annual cycle still occurs today, what remains unclear is what the future holds for a species that, over the last half century, has been defined by precipitous declines.
Another 20 years of hunting and fishing, coupled with additional dams, irrigation projects, and other infrastructure had decimated gharial populations and damaged the species’ habitat. In the last 50 years, Lang says, the species has ceased to exist in six locations. By 2025, it’s expected to disappear from four more. Already gone from more than 90 percent of its original range, the gharial is now limited to 14 populations. Just five of these are actively reproducing. Most groups contain fewer than 50 individuals of breeding age (10 to 15 years old for females, 20 to 25 for males). Today, there are just 650 to 700 mature gharials, living only in India and Nepal.
The relatively healthy breeding population on the Chambal is precisely why the massive 2008 die-off here caused such alarm. The Chambal contains nearly 80 percent of all the gharials left on Earth. It is the only population large enough to be stable, says Perran Ross, a crocodile expert at the University of Florida in Gainesville, and co-author with Lang on the latest IUCN Red List assessment, which is currently under review.
“In that one die-off, a huge proportion of what we thought were there died,” Ross says. “It’s not a good thing to lose 100 of a critically endangered species.”
Early theories focused on widespread pollution. Based on a variety of clues, however, Lang suspects illegal or accidental dumping of the non-steroidal anti-inflammatory drug diclofenac that was once commonly used on livestock but was banned in India in 2006. A few years earlier, also in South Asia, the drug was responsible for a sharp decline of vultures, which all showed signs of kidney dysfunction like the dead gharials examined in 2008.
Definitive proof has remained elusive, and fortunately another gharial die-off has yet to come. In the meantime, as Lang and his team began to monitor various threats and population trends, they found a sign of hope: There were more gharials than they had expected to see on the Chambal. Before the die-off, annual counts by the local forest department had produced the estimated total of 200 to 250 adult gharials that was often repeated at the time. But even after more than 100 gharials died in the winter of 2008, there seemed to be plenty of the animals in the river. “That sort of opened our eyes,” Ross says, “that something was wrong with the population estimates.”
But threats remain, including the illegal extraction of sand and gravel to make concrete, as well as the tapping of the Chambal’s waters to irrigate seasonal crops along the riverbanks. The greatest threat, according to Whitaker, is the rising demand for water in one of the driest regions of India, home to millions of people who need the precious resource to survive. Managing this demand in order to balance the needs of people with the requirements of gharials and other wildlife in the Chambal will require creative solutions.
Although a decade has passed since 110 gharials mysteriously died here, experts know that a similar catastrophe could happen again. That possibility has added a simmering sense of urgency to research and conservation efforts along the Chambal. The die-off also illustrates the potentially catastrophic consequences that disruptions to water bodies can have on aquatic species that are close to the brink. For a species that is struggling, the fate of this river will determine its future. “If the species is going to survive,” Lang says, “it’s going to survive in the Chambal.”
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ABOUT THE Photographer
Dhritiman Mukherjee is one of India’s most renowned nature photographers. He has received numerous national and international photography awards, including the 2014 RBS Earth Hero Award and the 2013 Carl Zeiss Conservation award. Mukherjee’s photos have been published inNational Geographic
,The New York Times
, BBC, and Lonely Planet, to name a few. He typically spends 300 days a year in the field, capturing photos in a wide range of habitats, from deserts and rainforests to mountaintops and rivers. Mukherjee recently published a book titled “Magical Biodiversity of India.”
ABOUT THE Writer
Emily Sohn is a freelance journalist in Minneapolis whose stories have appeared inNature
,The Washington Post
, and many other publications.
Emily Sohn Dhritiman Mukherjee
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