The curious case of the tigers who changed their stripes
Decades ago, India’s tigers were on the brink of extinction. Slowly, their numbers have rebounded. But that ecological success has prompted a dire problem—and a race to save many of them from genetic collapse.
It took 50 days of searching before the jungle revealed its biggest secret to us. Fifty days of jostling along gravel roads in the Similipal Tiger Reserve, in India’s eastern state of Odisha, scanning between trees in the semi-evergreen forest, hoping for a glimpse of an elusive tiger called T12, whose striking appearance has made him a symbol of a population at a perilous crossroads.
My partner in the quest, Raghu Purti, a staffer with the regional forest department, had never set eyes on T12. Most of his colleagues had only ever seen the tiger in images from camera traps set up to study animal movements throughout the reserve. But actually laying eyes on Similipal’s tigers lets forest officials look for physical ailments that cameras may not capture—and also provides a reminder that there’s a living, breathing purpose to the countless hours they spend patrolling in the sweltering heat. A documented sighting of T12 would be particularly valuable, since the reclusive 10-year-old tiger—the eldest male in Similipal—was right then at the heart of a plan to ensure the survival of future generations.
It was late in the afternoon of day 50 when, in the blink of an eye, a dark shape dashed out in front of our pickup truck. I slammed on the brakes. Ahead of us, spanning the width of the road, an enormous tiger stared back at Raghu and me. It was an older male—clear from its size—and it had exactly the strange, distinctive coat we’d been looking for.
“It’s black,” Raghu said, in an insistent whisper. He pointed excitedly and repeated himself. “It’s black!”
The tiger, T12, had dark fur that draped over him like a ragged cloak. Slivers of orange peeked through along his body, with thicker patches appearing on his face and front legs. This uncanny widening of a tiger’s black stripes, a rare genetic mutation known as pseudo-melanism, is shared among roughly half the 30 or so tigers that roam the Similipal reserve. And it’s an indicator of a conservation success story facing a potentially catastrophic complication. Because while the number of tigers in Similipal is more robust than it has been in decades, the reserve is geographically isolated from other tiger populations—a tiger island, so to speak, with a dangerously dwindling gene pool.
But during the weeks that Raghu and I scoured the area for T12, work was under way elsewhere to find him a suitable mate. It was a crucial step in a targeted breeding program years in development, a mission shared between conservation agents and a team of groundbreaking molecular ecologists and genetic experts all working to save the tigers of Similipal from inbreeding themselves out of existence.
In many ways, India’s tigers have faced the same challenges as big cats throughout the world have, hunted to near extinction by trophy hunters amid relentless habitat destruction and fragmentation. In the 1970s alarm over the iconic species’ decline prompted the establishment of a state-run reserve system. But the reserves lacked coordinated monitoring and enforcement until 2005, when India created a dedicated central agency, the National Tiger Conservation Authority (NTCA), which today hires and trains rangers, manages scientific oversight, and guides habitat preservation across 58 reserves.
A key concept underlying the reserve system is that tigers are typically able to travel between protected areas using what are known as natural corridors—patches of connecting forest and other prey-abundant lands. There are a number of benefits to these corridors, but the most important is that they encourage breeding among neighboring tiger populations, improving genetic diversity. Similipal, at a little over a thousand square miles, is one of India’s largest reserves, and its closest neighboring ones—Satkosia to the southwest and Sundarban to the east—are both more than a hundred miles away, which isn’t too far for a tiger to walk.
But there are no tigers left in Satkosia. And no adequate corridor connects Similipal and Sundarban. The land between them is mostly urban or agricultural—Kolkata, its suburbs, and a vast area of rice fields—with very little forest cover, which is where tigers prefer to stay hidden. Dozens of towns and villages separate Similipal from its two neighboring reserves as well. For tigers, there is just no easy way in or out of Similipal.
When the NTCA surveyed wild tigers across India in 2006, the tally was roughly 1,400 animals—down from an estimated 40,000 a century before. In Similipal, the population bottomed out at just four tigers, in 2014, only one of them male. But in 2015, a year or so before he died, the male fathered T12, with his strange, predominantly black coat. And T12 has since fathered male cubs of his own.
India’s tiger population has begun to rebound over the past 20 years, thanks in large part to the conservation work of the NTCA and forest officials. As of a 2022 estimate, the country is home to more than 3,100 tigers. And as Similipal’s population climbed slowly but steadily over the past decade, the growing number of tigers at first seemed like a microcosm of the national success story. Soon, though, the reserve’s managers began noticing more and more young tigers sporting the same dark coat as T12. The mutation, as far as both foresters and genetic scientists can tell, is harmless, merely a cosmetic oddity caused by a random and naturally occurring quirk of DNA.
But, experts say, it is also a tangible manifestation of a very real problem. If this mutation was able to pass so quickly through Similipal’s population, with all the tigers sharing very similar genetic makeup due to rampant inbreeding, then so too could more serious abnormalities. Now the task facing some of India’s foremost tiger authorities has shifted from recovering tiger numbers to breaking this cycle of inbreeding before it’s too late.
Playing genetic matchmaker for tigers is tricky. In order to find the ideal breeding partners for T12 and his offspring, the would-be saviors of Similipal needed to understand the differences among not only the tigers that roam today but also the tigers of the past.
That’s what led molecular ecologist Uma Ramakrishnan, not long ago, into a dimly lit trophy room in a grand home in Akaltara, a small town in central India. Ramakrishnan, a National Geographic Explorer and the head of a lab at Bengaluru’s (Bangalore) National Centre for Biological Sciences, was invited there by Anupam Singh Sisodia, whose family had once held the role of chieftains across 51 villages and the surrounding forests and farmland, responsible for protecting the locals from dangerous wildlife. His family had done its share of hunting, and the room was full of mounted black bucks, sloth bears, and four-horned antelope collected between 1920 and 1970. But laid out on a table before Ramakrishnan was a set of tiger pelts, their massive heads intact and seemingly snarling.
“Killing problematic tigers,” Sisodia acknowledged, “was more of a political necessity than a pleasure.”
Since 2005, Ramakrishnan and her fellow researchers and students at the lab have been collecting samples of tiger DNA in order to build an extensive genetic map of the diversity among India’s tigers. She’s secured roughly 250 specimens from historic estates like the Sisodias’. She has plumbed taxidermy collections at sites like the Natural History Museum in London and ventured into Indian jungles to procure scat, blood, hair, and saliva from live tigers. All that evidence has given her critical insight into how the animals have changed over generations as they moved throughout the region.
Closely inspecting one of the tiger heads, Ramakrishnan slid her scalpel into the 80-something-year-old pelt. Practiced and precise, she sliced off a small piece. She slid the sample into a vial and held it up.
“This is the real treasure,” she said.
When Ramakrishnan first began building her DNA database, her goal was to answer questions about tigers that couldn’t be answered by observing them in the field. As their population was decimated, tigers lost not only territory but also substantial genetic diversity. Historical DNA offered important clues about what else might exist within the gene pool.
Her research became ever more relevant in 2017 when the NTCA, alarmed by the dark-coated tigers in Similipal, asked her to formally study the reserve’s tigers. The forest officials clearly saw that the impacts of the reserve’s isolation were becoming measurable. They hoped Ramakrishnan could both verify the genetic culprit and help them find a solution.
Once she took a closer look at the animals sequestered within the reserve, Ramakrishnan quickly realized that the recessive pseudo-melanism gene was spreading through the population. The genetic isolation on display, she said, was a ticking time bomb—left unaddressed, it could prove devastating to the reserve’s tigers.
It’s impossible to know precisely what other maladies genetic mutations among big cats might introduce. But when Ramakrishnan and her colleagues analyzed a genetic mutation dataset for the closest available comparison—domestic cats—they found that these not-so-distant cousins faced issues like retinal atrophy, kidney disease, and hyperthyroidism. And with female tigers averaging litters of two to three cubs every two to three years, health issues can quickly and dramatically compound.
“We’re still trying to understand the full impact of this inbreeding,” she says. “But one thing’s for sure—there’s no upside to this kind of genetic erosion.”
Given Similipal’s lack of connection to other reserves, Ramakrishnan’s recommendation was that wildlife managers identify a few tigers from a separate reserve and translocate them. Once in Similipal, the tigresses (the forest managers elected to move females) would hopefully reproduce with T12 or with his male offspring, which have begun to claim pieces of T12’s territory as they mature and have cubs of their own. This, Ramakrishnan said, would begin the overdue effort to diversify the reserve’s genetic pool. By comparing Similipal tiger DNA to the array of records in her dataset, she found that the most genetically diverse tigers with the lowest chance of more negative genes showing up in any future offspring were located in a reserve called Tadoba-Andhari, in the dense teak forests of the district of Chandrapur, halfway across India.
Of course, Ramakrishnan knew that identifying the right reserve is one thing. Actually moving a 300-pound wild animal hundreds of miles across the country is another.
One morning last fall, Ravikant Khobragade stood up from his spot in the open-air back seat of a two-door Maruti Gypsy and looked out onto the Chandrapur landscape. The wildlife veterinarian turned his attention to his ace shooter, Ajay Marathe, who was cradling a tranquilizer gun, and gestured to a young tigress just up ahead.
“I can see her. She is sitting in that bush ahead looking at us,” Khobragade said.
The tigress, later named Jamuna, was 28 months old and had spent all her life in or near the Tadoba reserve. Her youth meant she hadn’t yet established territory there. And, crucially, she had no history of conflict with humans. Both of these things made her a prime translocation candidate.
(In another dense Indian forest, tigers and leopards are thriving.)
Translocation work, particularly for animals as large and territorial as tigers, is highly sensitive under any circumstances, and in India’s tiger reserves, it requires a large number of verifications and approvals before it can proceed. High on the list of considerations is whether an area identified as having candidates has a population healthy enough to withstand losing breeding-age females. In Tadoba, this is not a concern.
Although the reserve is two-thirds the size of Similipal, it is home to roughly 95 tigers, and it is no tiger island: Natural corridors connect Tadoba to the Umred Karhandla Wildlife Sanctuary around 40 miles to the north, the Nawegaon-Nagzira Tiger Reserve 70 miles to the northeast, and the Kawal Tiger Reserve 70 miles to the southwest. Tadoba’s tigers regularly venture out in search of more forested space. And as their numbers have swelled over the past decade, all that movement has meant that tigers and people in the surrounding mosaic of forests, villages, and farmlands have had to learn how to live alongside one another again. Most important for T12 and his kin, the network of connected reserves has allowed for a constant exchange of tiger genes.
Jamuna would be the first of two Tadoba tigers translocated to Similipal in a matter of weeks, with others to potentially follow in the coming months and years if the experiment went well. But first, she needed to be sedated.
“Is the dart ready, sir?” asked Marathe.
The tigress rose from her spot in the bush and marched closer to their vehicle. When she was around five yards away, Marathe calmly removed the safety key from his dart gun, brought the scope to his eye, and took the shot. The pink-tailed projectile landed in Jamuna’s thigh, prompting a loud growl that echoed across the landscape as she bounded away. She made it about 200 yards before the tranquilizer took its toll. The team found her laid out in a meadow.
It took seven men to carefully slide Jamuna onto a stretcher and move her into the shade. Khobragade checked her for injuries and drew a blood sample. After he fixed a GPS collar around her neck, the team moved her into a metal cage aboard a truck. Once safely inside, Jamuna was given a revival drug. Within minutes, the men heard rustling and banging, the sound of her nails scratching against metal, followed by a roar.
The road trip to deliver Jamuna to Similipal took 28 hours. The truck was joined by a small convoy of support staff. The route had been carefully mapped to circumvent major cities and other areas where loud noises could cause Jamuna distress. Every few hours, the vehicles pulled over for a while to allow her to rest.
Finally, the door opened and Jamuna leaped through the gate leading into her new home, a two-and-a-half-acre enclosure in Similipal, where she spent almost two weeks acclimating. After that, the gate opened once more, this time with no cage on the other side. She was set free into the territory of T12.
When it comes to restoring diversity among India’s wild tigers, one critical step remains solely under nature’s control: mating. And tigers engage in selective courtships before they breed.
So in November, less than a month after Jamuna was released into the reserve, a second female tiger from Tadoba, called Zeenat, was sedated and transferred to an enclosure in Similipal. Whereas Jamuna settled in the Similipal landscape with relative ease, the stress of the relocation took a greater toll on Zeenat, and she quickly wandered beyond the reserve’s borders. The forest department, not wanting her to stray too far, sent a team out to tranquilize her and bring her back to spend several more weeks in an enclosure to acclimate before she was released into T12’s territory.
Both she and Jamuna wore GPS collars so that forest officials could track their movement and behavior. Knowing where the tigers were, forest officers on the ground used night vision cameras to observe them from a safe distance. They kept a close eye on the pair to see whether either of them would cross paths with T12 or other males.
But the observers only saw Jamuna and Zeenat alone. Tiger courtship, by contrast, is conspicuous. A pair of mating tigers might spend weeks together, walking through the forest and vocalizing. Yet as the tigresses established territory in Similipal, forest officials never saw any evidence that they’d so much as had contact with T12.
Until one night in May. Reviewing the feed from a mounted camera that takes thermal and visual images, the forest department captured footage of Zeenat with T12. It was unmistakable evidence: Their mating ritual had begun.
The courtship sighting signaled that the genetic rescue mission, if not yet an outright success, holds promise. Meanwhile, this summer, as the teams behind the translocation awaited Zeenat’s first litter of cubs, the work continued. Ramakrishnan and her students collected more hair and scat samples left behind by Similipal tigers to better understand the genetic variation within the population. Officials are hopeful that Jamuna will eventually find a mate. And everyone working in Similipal is eager to see whether Zeenat’s cubs are born with T12’s pseudo-melanism.
It’s not yet decided whether or when the reserve will receive more translocated tigresses—or how many more might be needed to introduce sufficient genetic variability. But until a corridor links Similipal to other populated tiger reserves, more translocations could be the only viable option. Looking ahead, Similipal field director Prakash Chand Gogineni said his personal hope is that Similipal’s tigers can become a source population that helps return the species to places like the nearby Satkosia reserve. That might happen with the help of a translocated Similipal tigress or perhaps via new corridors, even if the latter are still likely decades away.
Witnessing all of this firsthand, seeing the pitfalls that India’s tigers face as they begin to make their comeback, returns me to certain moments from my childhood. I grew up on a farm not far from Chandrapur, where my life revolved around animals and jungles, for better and for worse. Naming pet dogs was painful, as leopards regularly took them away. And every now and then we would encounter a pugmark similar to a leopard’s but much bigger. The air would fill with fear and excitement at the realization we were sharing space with a true apex predator. The experience of living alongside something that powerful and elusive shaped how I saw the forest and my place within it. I never came across a tiger at our farm. But I often dreamed of it.
In the years since, I have seen, studied, and photographed countless tigers. But none of them looked like what I saw that day in Similipal while sitting in the idling truck with Raghu. Locked in a momentary staring contest with T12, I didn’t reach for my camera. I didn’t move. There stood a black tiger, a testament to humans’ best intentions gone wrong. In the best-case scenario for Similipal, this will someday be a rare and unforgettable creature. One that inspired a new discipline for safeguarding the species. In that moment, for four seconds in the roadway, it felt like a miracle of nature. Then, without a roar or a snarl, T12 took a few powerful strides and vanished into the thick evergreen forest.
(Discover more from this photographer on footbridges in Meghalaya and Himalaya ghost cats.)
The nonprofit National Geographic Society, committed to illuminating and protecting the wonder of our world, funded the work of National Geographic Explorer and photographer Prasenjeet Yadav featured in this story.
An Explorer since 2014, Yadav spent nearly 14 months reporting and photographing this story. For his last National Geographic assignment, he captured incredible images of snow leopards in the Indian Himalaya.
