World’s biggest maternity ward? Over 41,000 giant turtles found nesting together in the Amazon

A remarkable scene from the Amazon is drawing global attention. Along the Guaporé River, which runs between Brazil and Bolivia, scientists recently spotted an enormous gathering of giant South American river turtles coming ashore to lay their eggs. The number was striking.

Researchers say that more than 41,000 turtles gathered at the site, making it the largest known nesting place for this endangered species. The study was done in 2025 by the University of Florida (UF) and the Wildlife Conservation Society (WCS) and was later published in the Journal of Applied Ecology.

Counting turtles from the sky

The giant South American river turtle, also called the Arrau turtle, is one of the largest freshwater turtles in the world. As mentioned in a report by Discover Wildlife, some can grow up to 90 centimetres long and weigh nearly 80 kilograms.

Every year, female turtles gather on sandy riverbanks to lay their eggs. But counting thousands of turtles across a wide area is not easy. Researchers say traditional methods often take a lot of time and can disturb the animals.

As mentioned in the report, lead author Ismael Brack explained that counting animals directly on the ground can take a lot of time, disturb the wildlife, and may not always be accurate. He said that using drones to take aerial photos is a quicker and less disruptive way to count animals, although this method also has some limitations.

To improve accuracy, the research team marked 1,187 turtles with white paint on their shells. According to the report, over the next 12 days, drones flew over the nesting area several times a day, capturing thousands of photographs from above.

Later, these images were stitched together to create detailed maps. This helped scientists track the turtles and see which ones were moving, resting, or returning to the same spots.

A better way to estimate the population

Even with drone images, counting animals can still be tricky. Turtles move around; some may get counted twice, and others might not appear clearly in photos.

To deal with this, the team used statistical models to correct such errors. The results showed how much estimates could vary depending on the method used.

As mentioned in the Discover Wildlife report, ground surveys counted about 16,000 turtles, while basic drone counts suggested almost 79,000. After applying the improved model, researchers estimated the actual number to be around 41,000 turtles.

“These numbers vary greatly, and that’s a problem for conservationists,” says Brack, as quoted by Discover Wildlife. “If scientists are unable to establish an accurate count of individuals of a species, how will they know if the population is in decline or whether efforts to protect it are successful?”

Why protecting these turtles matters

Giant river turtles play an important role in the Amazon ecosystem. They help spread seeds and also become food for other animals, helping maintain balance in the river environment.

Because of this, scientists say getting accurate population counts is essential. It helps conservation groups understand whether their efforts are working and where protection is most needed.

Brack also pointed out that the same counting approach could be useful for other animals that move frequently, such as seals, elk, or mountain goats.
Thumb image: Canva (for representative purposes only)