"To see her standing there, focused entirely on finding her cub – who was in serious danger – was one of the most affecting things I've ever seen."

On a stretch of river near Bardia National Park lies a 4km² island that has become one of the most remarkable tiger strongholds on the planet.

Nobody had ever filmed here before David Attenborough’s Asia, and what the film crew found gave producer Patrick Evans the idea to return for a deeper investigation. When he asked me to be involved, it was the easiest ‘Yes’ I’ve ever said.

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In February, when we arrive, it’s so cold that your breath sits in front of you. By May, the sweltering heat has taken over and the same place feels louder and more exposed, the air thick with insects and birdsong.

This is one of the last places on Earth where tigers, elephants and rhinos still move through the same ecosystem at meaningful densities. But it is no untouched wilderness. This patchwork of forest, floodplains and community land is shaped as much by people as by wildlife. It is productive, busy and unpredictable – and then there is the island.

Nepal’s tiger story is one of the genuinely good news items in conservation. In 2010, the government committed to doubling its tiger population by 2022 and, remarkably, it got there ahead of schedule, with numbers rising from 121 to an impressive 355. Bardia National Park has been a big part of that, spearheading decades of protection, anti-poaching effort and, crucially, the involvement of local communities.

Picture Shows: Tigress named locally as "Goma", Western Nepal.

The island is what that success looks like up close. I have spent more than a decade studying big cats, and I learned very early on that seeing these predators is rare. Despite their sometimes enormous size, large felids are mysterious, secretive and expert at avoiding people. To understand them, you often need to build a picture from fragments: a paw print in soft mud, a scrape on a tree trunk, a faint smell of musk at a marking site.

But as I was going to find out, the island is something entirely different.

Tiger Island

The first step in production of the series, Tiger Island, was to deploy and collect footage from a network of remote cameras. These were positioned on well-worn tiger paths and near known nursery sites – females prefer areas of thick undergrowth, where they can hide their cubs until they are around three months old. When we started checking the images and saw tigers in almost every frame, almost every day, it took a moment to accept what we were looking at.

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The island is in an area of community-owned forest. It is uninhabited, but villages lie nearby on adjacent land. During the dry season, water levels fall and the landscape connects in ways that make the boundaries between wild and human space feel very thin.

It is a beautiful mosaic of tall grassland, riparian forest, sandy riverbanks and shallow channels, and, as we discovered, home to two male tigers and three females, each with cubs. In total, we documented 17 tigers moving through this small space.

We would see the same individuals, identifiable by their unique coat patterns, at the same remote camera sites, sometimes within hours of each other. Such density is highly unusual. In most wild settings, tigers maintain vast territories that can extend to as much as 400km² in parts of Siberia, because prey is thinly distributed.

Picture Shows: Tigress named locally as "Goma", crossing a river back towards her island territory. Western Nepal.

But on Tiger Island, that traditional biology is turned on its head. It makes sense. Prey, particularly chital deer, is abundant here, a result of seasonal flooding, managed grassland and water sources. The rivers hem everything in, and farmland and villages occupy the space beyond. Prey concentrates, and the tigers follow.

As well as filming the cats, we wanted to understand what was going on – how animals that are built for solitude are managing to live virtually on top of each other, and what that means more broadly.

We spent eight weeks on location, across two separate expeditions. We based ourselves adjacent to the island, crossing the river at first light, laden with the technology critical to our mission. Tigers are most active around dawn and dusk, so we’d aim to be in position early, staying until after dark most days.

Our core team was small: just me and camera operators Anna Dimitriadis and Max Hug Williams, alongside three tiger trackers. Sushila, Manju and Ranju Mahatara are sisters who grew up here, and have an understanding of the territory that no outsider could ever replicate.

Their ability to read the landscape is unsurpassed, and they know more about these tigers’ movements than anyone. They’d see a pugmark or a scrape on a tree and know instantly which animal had made it and how recently. Within minutes they’d have an idea of where it was heading.

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A broader team of drone operators, producers, fixers and drivers helped us maintain near-continuous coverage across the island. We kept in constant radio contact and if a tiger was spotted, we would get to the location as quickly as we could, on foot or by quad bike. The island has no paved roads, which meant venturing into the heart of a very wild and unforgiving landscape.

Visibility on tiger island comes and goes. In some places, the grass is tall enough to hide a rhino (and more than once it was doing exactly that). When walking in an environment like this, you stay alert, experiencing a primal awareness that only comes when you’re on the ground alongside megafauna – it’s a relic of what our ancestors would have needed in order to survive.

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The three tigresses

Tiger Island tells the story of its three tigresses: Goma, experienced and steady, a matriarch with two cubs; Mala, Goma’s daughter (from a previous litter), now with three cubs of her own; and Jugni, possibly another relative of Goma’s, also mother to three cubs.

Each female has her own territory, areas of which overlap. Related females can tolerate some level of crossover, but the extent of it here felt very tight. The resident male, Bandheil, held a territory encompassing all three females.

The ever-present fleet of drones was one of our most invaluable tools to uncover the tigers’ secret lives. From the air, behavioural patterns emerged that would have remained unseen by cameras on the ground and undetected by traditional research methods.

We could see how often individual tigers crossed paths and pinpoint how small their ranges really were. We witnessed cubs beginning to test the boundaries of their world, brand new social dynamics and intimate parenting moments. We captured incredible sequences of Mala’s playfighting cubs and of Goma targeting chital deer with laser-focused precision, dragging her kills back through dense cover.

Picture shows: Tigress named locally as "Goma", crossing shallow river with her two cubs. Western Nepal.

A new arrival

It was early on that a new male appeared on one of the remote cameras. He was identified as a newcomer, as none of his facial or flank patterns matched our ID guide – a tiger’s stripes and markings are as unique as a human fingerprint. Sushila and Manju named him Anjan, meaning ‘stranger’. He’d likely come from the national park, drawn by the prospect of finding a territory of his own with a high concentration of females.

A new male quickly changes things. Infanticide is well documented in tigers: an incoming male will routinely kill cubs that aren’t his, which brings the females back into breeding condition faster. In the days following Anjan’s arrival, our females became less predictable. They turned up in unexpected places, keeping their cubs close and shifting their core areas.

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Goma, despite her experience, was not immune to the pressure. During a tense moment, she became separated from her cubs. One of them had crossed the river to the village on the opposite bank, where a wedding was in full swing. Goma appeared in full view of the crowds and started calling across the water. She stayed there, even with so many human eyes on her.

Wild tigers just don’t do this sort of thing. They avoid people, especially in broad daylight. To see Goma standing there, focused entirely on finding her cub, who was in serious danger, was genuinely one of the most affecting things I’ve seen in years of doing this kind of work.

The risks to humans in this landscape are constant, yet it is worth clarifying that tigers are not usually the primary concern, as they tend to shy away from people. Rhinos and elephants are far less predictable and account for significantly more dangerous encounters and fatalities. We experienced several moments that reinforced this emphatically.

One morning, we were at the drone camp, the staging point on the riverbank from which the team flew and managed the aerial equipment, when an adult rhino emerged from the water and started heading our way. It kept coming, closing the distance with a deliberate purpose that quickly became uncomfortable.

When it reached a critical point, the ranger team, led by Sushila, stepped in, making enough noise and movement to give the animal pause. The rhino grunted, swung away and disappeared at a trot into the long grass, becoming swallowed almost immediately by the vegetation. It was very unnerving, yet an entirely routine interaction by the standards of this landscape.

Success and its complications

From a conservation perspective, the island is both encouraging and complicated. The increase in Nepal’s tiger population is a success story that reflects decades of committed work by government agencies, NGOs and local communities, yet it also brings tension. Higher densities bring more overlap, more competition and thus greater potential for conflict, both between tigers and, at the margins of the park, with people.

What we observed while filming Tiger Island contradicts what we thought we knew about tiger biology. These individuals are adapting to conditions that wouldn’t have existed a generation ago, demonstrating behaviour that we haven’t properly documented before. That’s hugely exciting.

You learn a lot when you stay with animals long enough. Not just about what they do, but the texture of it – how they shift when things change, how they use space, how they seem to read each other. And I don’t think this island is a one-off. There will be other islands, corridors and patches of forest where large predators are living in ways we haven’t caught up with yet.

And that’s what I keep coming back to. Not just what we found on this particular island, but the sense that there’s a lot more out there that we humans are only just beginning to discover with the tools we have now. Even with a species as globally loved and studied as the tiger, there’s still so much to learn.

Watch Tiger Island on BBCI Player

All pictures @ BBC Studios