Australia Released 100 Bilbies Into A Fenced Desert . What They Did To The Earth Changed Everything.

By 1912, the Greater Bilby had disappeared from New South Wales. The soil compacted. Native seeds stopped germinating. The mammals that had managed that land for tens of thousands of years vanished and almost nobody noticed. On a moonless night in September of 2024, two ecologists drove into the far northwest corner of New South Wales, opened the latches on plastic carriers, and released 100 bilbies into Sturt National Park. A small experiment in the wild training zone more than a century after the species had vanished from the region. At first, scientists expected slow ecological responses. Maybe some burrowing. Maybe a few native plants taking hold over time. Within the first years, the team at UNSW Sydney found something they had not anticipated. Soil samples from the rewilded ground showed changes the surrounding desert did not. Surveys documented darker patches around the pits, unseen for a century. How did one of Australia's smallest marsupials, with nothing but a long snout, oversized ears, and a few thousand foraging pits per hectare, outperform a century of failed restoration? This is the story of how Australia accidentally rebuilt a piece of desert with the most overlooked animal on the continent. If you're interested in these questions, subscribe. These are just the first ones. Before we get to how, we have to go back. To the ships, the colonists, and a chain of events that emptied a continent. The bilbies did not vanish on their own. They vanished the same century three other animals arrived from across the world. The British colonists landed in 1788. Their ships carried cats, kept aboard to manage rats. The cats jumped ship and spread inland faster than the colonists. In 1855, red foxes were released into Victoria for sport, a deliberate introduction of a new predator into an ecosystem that had never seen one. Four years later, 24 rabbits were turned loose near Geelong. Within 50 years, their descendants had colonized two-thirds of the continent. The chain reaction was severe. Rabbits stripped the vegetation. Exposed natives became dinner for the cats and foxes. A loop. The desert could not break. Feral cats alone now kill around 1.5 billion native animals a year, linked to at least 20 modern mammal extinctions in Australia. In most of the world, extinction risk falls on large species. In Australia, it came for the small. Mammal biologists call the critical weight range between 35 grams and five and a half kilograms. The ones that fit inside a cat's appetite. Bandicoots, bettongs, quolls, mulgaris, bilbies. By the early 20th century, the bilby had vanished from New South Wales. By the 1990s, it survived only in fragments of Western Australia, the Northern Territory, and a corner of Southwestern Queensland. 70% of mainland Australia reduced to less than 20. A small marsupial that digs for a living is not just a species. It is a job. When the bilbies disappeared, that job stopped getting done. The desert kept looking like a desert. But the workforce that had run it for 50,000 years had been quietly fired. So what exactly did that workforce do? And could putting it back undo 100 years of damage? Ecologists call animals like the bilby ecosystem engineers. Beavers shape watersheds with dams. Elephants convert forest into grassland by toppling trees. The bilby works through one behavior. It digs. A bilby weighs about one kilogram for a female, up to two and a half kilograms for a male. It does not drink water, pulling every drop of moisture from what it eats. Termites, larvae, grass seeds, bulbs, fungi. According to Animal Diversity Web research, bilbies press an earflap against the ground and hear termites moving in tunnels below the surface. When they hear one, they dig a pit up to 25 centimeters deep. They eat what they find, walk a few meters, and dig another. Every night. For about five to six years in the wild. According to Taronga data, a single bilby can shift up to 3.6 tons of soil per kilogram of body mass per year. Based on studies of digging marsupials where predator pressure is low, foraging activity can produce thousands of pits per hectare a year. The population also replaces itself faster than almost any other mammal. The greater bilby has one of the shortest mammalian gestation periods, 12 to 16 days. A healthy female can produce up to four litters a year. From 10 founders, a colony can build itself in a single rainfall cycle. Picture a small city. Streets, houses, electrical grid, all functioning. Then the sanitation department disappears overnight. Within months, garbage piles up. The soil stops absorbing rainwater. Within a decade, the city looks the same on a satellite map and works almost nothing like one. That is what happened to a desert without its ecosystem engineers. A fair question. If digging mattered so much, why didn't feral rabbits fill the gap? Geometry. A rabbit warren is a horizontal tunnel below the surface, and rabbits compact the ground above through grazing, turning the soil into a hard pan that sheds water. A bilby pit is the opposite shape. A vertical cone that catches leaf litter, traps seeds, and funnels rain into the soil. Comparative studies have found higher seed retention and germination in native pits than in rabbit diggings. Rabbits also graze the vegetation that should feed those pits. Opposite forces, same ground. Two ecologists figured out how to test this. Dr. Rebecca West and Dr. Rhys Peddler, with Professor Richard Kingsford of UNSW Sydney, founded Wild Deserts Inside Sturt National Park, with NSW National Parks and Wildlife Service, Taronga, and Ecological Horizons. Their plan was not modest. Then it failed. In October of 2018, the project completed 40 kilometers of feral-proof fencing across two enclosures of 4 by 5 kilometers each. 40 square kilometers of sealed habitat ready for animals. The rain stopped that month. For nearly two years, the sky over Sturt stayed empty. The vegetation thinned. The team watched dust blow across the empty fence line season after season. The question hanging over the camp must have been a simple one. Had they spent five years building a tomb? In 2020, the rains arrived. What happened over the next three years did not resemble any conservation project Australia had attempted before. The fence was the first piece. The wild desert's perimeter is a layered exclusion system adapted from a design by ecologists Catherine Mosby and John Reed at Arid Recovery in South Australia. 1.15 meters of woven steel mesh formed the wall, with a 60 centimeter floppy overhang at the top. So a climbing cat reaches the lip, loses grip, and falls back. The fence skirts outward at the base, sunk into soil, so a digging rabbit or fox hits a horizontal apron of mesh. Inside the fence came the cleansing. Every rabbit, every cat, every fox within the perimeter had to be removed. Rabbits were eradicated through warren ripping and a viral biocontrol called RHDV. Foxes and cats were removed through cage trapping, baiting, and night shooting with thermal scopes. For maintenance, Wild Deserts deployed a device called a Felixi grooming trap. It used computer vision and laser rangefinders to identify a feral cat versus any other animal, then sprayed a measured dose of toxic gel onto its flank. Cats are obsessive groomers. They would lick the gel off and consume the toxin. Any other species walked past untouched. The first 10 bilbies, released into stirt in September of 2020, came from Taronga Western Plains Zoo in Dubbo. 30 more, released in May of 2021, came from wild populations at Arid Recovery and Thistle Island in South Australia. Funding came from the New South Wales Saving Our Species Program, which allocated 100 million Australian dollars to threaten species recovery between 2016 and 2021. The team did not build one enclosure. They built two. With a single fenced zone, you cannot separate the effect of the animals from the fence or the rainfall. Two enclosures, identical conditions, different management. A controlled experiment. In 2024, the project opened up. Outside the sealed exclosures, the team established the Wild Training Zone. Around 10,000 hectares enclosed by a conservation fence, where feral cats are kept at low densities On a single night in September of that year, 100 bilbies and 20 western quolls were released into the training zone. It was the first time in a century that bilbies had walked that ground without a sealed predator-proof fence between them and feral cats. The bilbies were out. Now the question was whether the desert itself would notice. Scientists predicted the bilbies would survive, breed, and slowly recolonize. What they did not expect was how quickly the soil itself would respond. Within the first year, researchers walking transects across the rewilded zone were counting thousands of fresh diggings per hectare. Bowl-shaped depressions. Conical pits. The team built a monitoring system as carefully engineered as the fence. Annual trapping. VHF radio transmitters on tagged animals. Motion-triggered camera traps. Track plot surveys at sunset to count species crossings by dawn. Soil chemistry measured inside and outside the enclosure. This led the team say with statistical confidence that what changed was the bilbies and not the rain. The pits were doing what ecology textbooks had predicted. Soil samples from inside them showed higher concentrations of labile carbon, the form microbes and plants can actually use. Water infiltration rates were dramatically higher. Seeds that had been blowing across the desert for years were lodging in them and germinating. The most visible change at ground level was color. The red sand of Sturt, undisturbed, sits in a flat, compacted crust ecologists call a biocrust. A thin skin of cyanobacteria, lichens, and mosses. Inside the rewilded exclosure, that uniform red was broken by thousands of darker patches. Each pit became an organic trap. Leaf litter fell in. Seeds fell in. Moisture pooled. Decomposition accelerated because conditions inside were sheltered, humid, and nutrient-rich. Based on the soil chemistry, the result was small patches of organically enriched soil scattered across the landscape. Given the density of pits the team was documenting, the cumulative pattern would likely have been visible from above, an effect the unmanaged side had not produced in a century. When researchers analyzed soil biology inside the pits, the bacterial and fungal communities had shifted measurably from those in the surrounding crust. Every foraging hole was a biochemical reactor in ground that, two years earlier, had been functionally dead. What was returning was not just a marsupial. It was a working chemistry that had been switched off for a century. The crest-tailed mulgara population, started with 19 founders, climbed to between 160 and 240 in three years. 13 Shark Bay bandicoots translocated in 2021 doubled in six months. Between 2024 and 2025, the team released 305 bilbies, 51 quolls, and 234 golden bandicoots into the wild training zone. Late 2025 monitoring confirmed bilbies and quolls had survived more than 12 months in the open. As Dr. Rebecca West put it, seeing their tracks in the red sand for the first time in a century was a thrill. One species, one set of fences, one change to the soil, and the entire system began to function again. But the numbers tell only part of the story. The change was visible, and the team had been documenting it from two angles at once. The team set up two motion-triggered cameras, same model, same height, pointed at similar patches of red sand. One inside the exclosure, one 100 meters outside in the unmanaged outback. Outside the fence, very little moved. Wind, an occasional cat or kangaroo. The crust stayed undisturbed across thousands of frames. Inside the fence, the same hours produced a different recording. Bilbies emerged from burrows and dug within meters of the camera. Bandicoots crossed the frame multiple times a night. Skinks sheltered in the pits by day. Birds dropped in to forage for insects. The inside ground was pocked with bilby pits. The outside remained flat and compacted. Same latitude, same rainfall, same temperature, same seed bank. The only difference was the presence of one species inside the fence and its absence outside. Wild Deserts now employs ecologists, technicians, and field staff in one of the most remote corners of New South Wales. Dr. West and Dr. Peddler raised their three children at the field station. Tourists once drove past Sturt without stopping and many now route their trips through the Talpero lookout. The state government has committed to expanding the model to 10 feral predator-free areas across New South Wales. And yet, the most important part of the project has not happened yet. The Wild Deserts roadmap calls for the reintroduction of seven locally extinct mammals over 10 years. Honesty matters here. The open release is still young. Feral cats remain at low densities and predation events happen. Whether bilbies can survive long-term outside sealed fencing has not been answered. It is being answered every night by every bilby that walks out at dusk, digs a few pits, and makes it back home before dawn. What the project has demonstrated is something else. When the right animal returns to the right ground, it responds quickly. In a single rainfall cycle, the chemistry begins to shift. In three years, the changes are measurable. In five, other species begin arriving on their own. The most important pieces of an ecosystem are not always visible. Some work in the dark, doing one task no other species performs the same way. When those engineers disappear, the landscape looks the same for a generation or two. And then everything that depended on them starts to fail. Wild Deserts has put a small piece of that vanished workforce back into one corner of an empty continent. The animal weighs less than a bag of sugar. It works after sunset. It does not appear in the tourism brochures. And yet, for the patch of red sand where it has been released, it may turn out to be the most consequential ecological intervention in 100 years. The next episode follows a botanist on the South Island of New Zealand who refused to follow national weed control law for 40 years and accidentally rebuilt one of the country's most diverse native forests in the process. If you want the rest of these in your feed, subscribe. The pattern underneath them is...