Picture a stretch of sandbank on the border between Brazil and Bolivia, baking in the July sun. Now picture it covered — almost entirely covered — by enormous turtles.
Forty-one thousand of them.
A team of scientists from the University of Florida and the Wildlife Conservation Society (WCS) has confirmed the **world's largest known nesting site** of the giant South American river turtle (*Podocnemis expansa*), also known as the Arrau turtle. The study, published in the *Journal of Applied Ecology*, reveals a single stretch of the **Guaporé River** as the most extraordinary turtle maternity ward on Earth — and it took drones to finally see it properly.
**The Turtle That Time Almost Took**
The giant South American river turtle is the largest freshwater turtle in South America. Adult females can weigh up to 90 kilograms and live for over 80 years. They were once found across the Amazon Basin in their millions, nesting in vast gatherings along riverbanks every dry season.
Then came centuries of hunting. Their eggs — large, oil-rich, and nutritious — were harvested industrially. Adults were killed for their meat and fat. By the 20th century, populations had collapsed across much of their range. Conservation status: endangered.
But the Guaporé River — forming part of the remote border between Brazil and Bolivia — has always been exceptional. Its relative inaccessibility has sheltered one of the species's last great strongholds.
**The Drone Revolution**
Counting tens of thousands of turtles on a sandbank is harder than it sounds. Traditional ground surveys are slow, dangerous, and prone to underestimating numbers — turtles move, scatter when disturbed, and nest at different times. Previous estimates for the Guaporé site existed, but researchers suspected the true scale was being missed.
Lead author Ismael Brack and his team turned to drones combined with advanced statistical modelling — an approach that compensates for turtles not captured in any single frame, accounts for movement, and generates population estimates with far greater accuracy than raw image counts.
The result: **41,000 adult female turtles** at a single nesting aggregation. The largest ever documented.
'We describe a novel way to more efficiently monitor animal populations,' says Brack. 'And although the method is used to count turtles, it could also be applied to other species.'
The implications go beyond turtles. The drone-plus-modelling methodology could transform wildlife surveys for everything from nesting seabirds to basking crocodiles — anywhere that traditional ground counts fail to capture the full picture.
**What 41,000 Turtles Mean**
For the giant South American river turtle, this discovery is both heartening and clarifying. It confirms that the Guaporé River system is one of the most important freshwater turtle habitats remaining on Earth — and that protecting it matters enormously.
The turtles don't just nest here; they gather in communal groups, their warmth helping to incubate eggs buried in the sand. Hatchlings emerge together, overwhelming potential predators through sheer numbers. The aggregation isn't just remarkable to witness — it's ecologically essential to the species' survival.
For conservationists, knowing exactly where the largest gatherings occur helps direct protection efforts: ranger patrols, egg protection programmes, and advocacy for the river's preservation from dam development and gold mining, which both threaten the Guaporé ecosystem.
**The Biggest Maternity Ward in the World**
Every year, tens of thousands of ancient, armoured creatures haul themselves out of the water and onto the sandbanks of the Guaporé — following an instinct encoded over millions of years. They dig. They lay. They return to the river. And somewhere beneath the sand, the next generation begins.
For a species that was being hunted toward oblivion within living memory, the sight of 41,000 nesting females is, in the deepest sense, extraordinary.
Nature, when given the chance, endures. 🐢
*Sources: Journal of Applied Ecology · University of Florida · Wildlife Conservation Society · Discover Wildlife / BBC (March 7, 2026)*