\u201cWe describe a novel way to more efficiently monitor animal populations,\u201d says lead author Ismael Brack. \u201cAnd although the method is used to count turtles, it could also be applied to other species.\u201d<\/p>\n
A drone flies over the giant South American river turtle nest site: Credit: Omar Torrico, Wildlife Conservation Society<\/p>\n
Counting giant river turtles<\/p>\n
The giant South American river turtle (Podocnemis expansa) \u2013 also known as the Arrau turtle \u2013 is one of the largest freshwater turtles in the world, reaching up to 90cm in length and weighing as much as 80kg. It can vary in colour from dark grey to brown or olive green. <\/p>\n
The turtle is known for its highly social nesting behaviour. Every year in July or August, females gather in large numbers along the sandy banks of the Guapor\u00e9 River (one of the major tributaries of the Madeira River in the Amazon basin) to lay their eggs. Yet despite legal protections, the species remains under threat from poaching and habitat loss.<\/p>\n
In order to conserve species such as the giant South American river turtle, it’s important to work out accurate population sizes \u2013 to know if the species is in decline or whether efforts to protect it are successful. But counting wildlife has always posed challenges for scientists, says Brack.<\/p>\n
On-the-ground surveys can be time consuming, invasive and inaccurate, he explains. Aerial photos taken by drones provide a faster and less disruptive way to count animals, but even this method has limitations. Animals move around, and it\u2019s easy to miss individuals or count the same one more than once.<\/p>\n
![\"Guapor\u00e9](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2025\/08\/Guapore-River-scaled.jpeg\")
Look closely and you’ll see the turtles’ nest site on the sandy banks of the Guapor\u00e9 River. Credit: Omar Torrico, Wildlife Conservation Society<\/p>\n
To tackle the issue of inaccurate counting, the research team used a more refined approach. At a site on the Guapor\u00e9 River, they developed a system to account for errors such as double counting or missed animals. The team marked the shells of 1,187 turtles with white paint and monitored their movements over 12 days using drones.<\/p>\n
Each day, the drones flew over the site four times, capturing 1,500 images per flight. These were stitched together into detailed orthomosaics \u2013 high-resolution composite images created from overlapping photographs. Scientists then reviewed the images, recording whether each turtle was marked and if it was walking or nesting.<\/p>\n
![\"Giant](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2025\/08\/Giant-South-American-river-turtles-1-scaled.jpeg\")
The researchers marked the shells of 1,187 turtles with white paint and monitored their movements over 12 days using drones. Credit: Omar Torrico, Wildlife Conservation Society<\/p>\n
Using this information, the team built probability models to better estimate the true number of turtles present. Traditional counts and counts based on drone images had very different results: ground observers logged around 16,000 turtles, while researchers who reviewed drone images and didn\u2019t account for animal movement counted nearly 79,000. The new method produced what the researchers believe is a more accurate estimate of 41,000.<\/p>\n
\u201cThese numbers vary greatly, and that\u2019s a problem for conservationists,\u201d says Brack. \u201cIf 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?\u201d<\/p>\n
Ground-level footage of the giant South American river turtles. Credit: Omar Torrico, Wildlife Conservation Society
\nWhy the study matters \u2013 and what’s next<\/p>\n
The giant South American river turtle plays a key role in the Amazon\u2019s ecosystem<\/a>. As seed dispersers and prey for larger animals, they help maintain a healthy balance in the riverine environment. Protecting their nesting sites is therefore vital, and accurate population estimates \u2013 such as those provided by this new drone-led approach \u2013 are key to this.<\/p>\n
![\"Giant](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2025\/08\/Giant-South-American-river-turtle-1-scaled.jpeg\")
Found in large rivers such as the Amazon and Orinoco, global populations of these turtles are declining due to poaching and habitat loss. Credit: Omar Torrico, Wildlife Conservation Society![\"Giant](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2025\/08\/Giant-South-American-river-turtles-2-scaled.jpeg\")
The study documented more than 41,000 giant South American river turtles along the Amazon’s Guapor\u00e9 River. Credit: Omar Torrico, Wildlife Conservation Society![\"Giant](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2025\/08\/Giant-South-American-river-turtles-scaled.jpeg\")
Drone captures a mesmerising aerial shot of the giant South American river turtles. Credit: Omar Torrico, Wildlife Conservation Society![\"Giant](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2025\/08\/Giant-South-American-river-turtle-scaled.jpeg\")
The giant South American river turtle is one of the largest freshwater turtles in the world, reaching up to 90cm in length and weighing as much as 80kg. Credit: Omar Torrico, Wildlife Conservation Society![\"Giant](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2025\/08\/Giant-South-American-River-Turtles-along-the-Amazons-Guarpore-River.jpeg\")
Next, the research team plans to perfect monitoring methods by conducting additional drone flights at the Guapor\u00e9 River nesting site and in other South American countries where the giant South American river turtles gather. Credit: Omar Torrico, Wildlife Conservation Society<\/p>\n