Counting Leopards by Recording their Roars

TA tiger’s roar is a distinctive sound. A repetitive pattern of harsh, guttural calls, often compared to the harsh music of a saw being pushed and pulled across the trunk of a giant tree. This “sawing” roar is also highly individual, shaped by each tiger’s physiology and ecology, and varies in measurable ways from one tiger to another.

Now researchers have discovered how to do this Differentiating between cheetahs in Tanzania By analyzing the different temporal patterns in their roar. The researchers were able to use their analysis of the cheetah’s roar to accurately identify the leopard 93 percent of the time, a method that could help conservationists track these big cats over much larger areas than they do now. Understanding population sizes of endangered species is crucial for conservationists and policy makers when it comes to managing landscapes.

Cheetahs are classified as vulnerable to extinction — and in some places in Africa they are now considered “locally” extinct — but they are difficult to study because they are nocturnal, solitary, elusive, and roam widely across home ranges of up to 300 square miles. . Nearly a third of Tanzania already has protected areas to preserve wildlife and ecosystems, but as the human population continues to grow, so too. Demand for land and resources. Habitat loss It is among the biggest threats facing cheetahs, increasing the risk of human-wildlife conflict: attacks on livestock, a target of the big cats, often lead to these conflicts.

The project required examining 75,000 hours of audio data, but it was a happy accident, says Jonathan Grocutt, lead author and Ph.D. Student at the University of Exeter. “We got really lucky,” he says.

Grocutt was working with another biologist named Matthew Wiggers to track animals in Nyerere National Park in Tanzania. They placed audio monitors and camera traps together in the same locations so they could not only capture video but also record audio of creatures passing by. Grocutt asked Wiggers if he thought they would hear the footsteps of cheetahs, since they are so stealthy in the wild.

To find out, they started listening to audio and video of the cheetahs, and noticed that as the cheetahs walked past the cameras, they were also making noises. This means they can sort through the audio data by noting the timestamps on camera traps when cheetahs appear. While audio data is captured continuously, the camera only captures recorded video when triggered by motion.

Grocott and his colleagues collected data from 50 camera traps paired with audio recording units across 174 square miles of Nyerere National Park in Tanzania. Over the course of 62 days, the researchers recorded 217 roars from seven members of one of Africa’s most elusive and solitary species. Once the roars were isolated, acoustic analysis algorithms allowed Growcott to determine whether the frequency lines of those roars could be used to identify individual cheetahs with surprising accuracy.

As the cheetahs passed in front of the cameras, they were also making noises.

The study of animal sounds, a field known as bioacoustics, has long been used to monitor birds, primates and marine species, but researchers have only discovered newly It began to be used on big cats in Africa. Beyond the challenges of finding cheetahs in the first place, Grocott says the appropriate technology is still emerging, as previous attempts to study the sounds of lions, wild dogs or spotted hyenas have mostly been done with handheld microphones.

“Those studies relied on going out and tracking animals, spending a lot of time in the field, and having to know exactly who you’re recording. It takes a lot of resources. And with the density of these animals so low, acoustic studies haven’t been done. Putting monitoring collars on cats, which is Another alternative, which is expensive, invasive, and risky for researchers.

Kirsten Young, a senior lecturer in ecology at the University of Exeter, who was not involved in Grocutt’s study, says there are limitations to acoustic monitoring for conservation purposes. “We need the animal to make sounds, and we know that there are periods when it is silent,” she wrote in an email. “If we can’t hear them, we don’t know they’re there.”

But capturing the sounds of species is often worth the long quest. Young is a marine scientist who studies the ecology of deep-diving whales. Much of her work relates to conservation. Besides facilitating population estimates, vocalizations can be an important indicator of animal behavior.

“It helps us understand what the animal is doing,” Young says. For example, sperm whales emit a special “squeak” when they search for food or catch their prey, which helps scientists locate feeding areas.

“Sound is a good indicator of the health of the ecosystem,” Grocutt says. “We need to measure these votes before it is too late.”

Main image: Los t / Shutterstock

• Summer Rylander

  Posted on January 13, 2025

  Summer Rylander (twitter | Instagram) is a freelance journalist based in Nuremberg, Germany. They cover foodways, responsible tourism, and preserving our biodiverse planet.

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