The world is grappling with the urgent challenge of protecting its biodiversity. Understanding how endangered animals navigate their shrinking and changing habitats is more critical than ever. Animals face pressures in search of safe routes and spaces to find food, shelter, and avoid danger. This is especially true for species that live high up in the trees, like the unique and endangered lion-tailed macaque found only in the lush but increasingly fragmented forests of India's Western Ghats.
Lion-tailed macaques are covered in black fur with a silver mane surrounding the face. They are named not for their mane but for their tail, which is long, thin, and naked, with a lion-like, black tail tuft at the tip. With fewer than 4,000 individuals left, these striking monkeys are clinging to existence in a complex, vertical world. A new study by researchers at the Centre for Wildlife Studies (CWS) sheds light on how these macaques use their forest home, revealing surprising flexibility in their movements and offering vital clues for their survival.
The big question the researchers wanted to answer was how these highly arboreal (tree-dwelling) primates, who are under pressure from human activity, actually use the space around them. It's not just about moving from one tree to the next horizontally; it's also about deciding which forest level to be on – the ground floor, the middle branches, or the high canopy penthouse.
To figure this out, the scientists followed two groups, or "troops," of lion-tailed macaques in Silent Valley National Park. One troop lived deep inside the park's relatively undisturbed core zone. The other lived closer to the park's edge, in a buffer zone where there might be more human presence or disturbance. They fitted some macaques with GPS trackers to record their location. But because these monkeys live in a 3D world, the scientists also used vertical space assessment and advanced movement modelling, allowing them to see where the macaques went and how they used the entire volume of the forest space, from the roots to the highest leaves.
While both troops spent most of their time in the trees, they used the vertical space very differently, and this seemed linked to how safe they felt. The troop living near the buffer zone, where risks from humans or predators might be higher, was incredibly cautious. They spent a substantial 94.2% of their time in the mid-level canopy, rarely daring to descend to the ground. They preferred staying on their forest ecosystem's safer, less crowded middle floors.
In contrast, the troop living deep inside the park's core zone was much more comfortable exploring. They frequently descended to the forest floor and ranged over a larger horizontal area.
Before the study, it was thought that lion-tailed macaques only came to the ground in degraded or fragmented forests. This study shows they can and do use the ground even in healthy forests, but they make a strategic choice not to if they perceive danger. Both troops also showed smart, strategic movement patterns, slowing down and making careful moves near important resources like fruiting trees or dense canopy patches that offered good travel cover. They didn't necessarily prefer the tallest trees but rather areas with dense canopy cover, like using a hidden network of leafy highways to move around. Despite the core troop having a larger horizontal home range, both troops had similar daily travel distances and similar 3D home ranges, suggesting the core troop was efficiently using the vertical space to access resources spread over a wider area.
“An animal’s movement reflects how it perceives its environment and balances food, safety, and survival, and is usually the first visible indicator of any response to changes around them. Our study found that even in the absence of disturbances, the macaques routinely explore and use the forest floor. However, these also have their risks in terms of exposure to threats, so it is essential to prioritize continuous canopy connectivity, and even more critical to incorporate three-dimensional space use in wildlife conservation planning.” says Sikha Hariharan a researcher at CWS and an author of the study.
This research significantly improves our understanding by adding the crucial third dimension, the vertical one, to how we think about wildlife habitat use and conservation. It moves beyond just looking at a flat map of a forest area and highlights the importance of the entire 3-dimensional forest structure, from the ground to the canopy. It also shows that these macaques are more flexible and adaptable than previously thought, capable of navigating complex environments.
“Lion-tailed macaques are an incredible endemic species from India, and our study highlights the importance of continued research into their ecology, behavior and space-use. This study provides critical insights for how we can support their movement in human-modified habitats and improve conservation outcomes for lion-tailed macaques, particularly in degraded habitats” says e Dr. Krithi K. Karanth, Chief Conservation Scientist and Director at CWS.
The study provides critical, fine-scale information needed to protect the endangered lion-tailed macaque. Conservationists can develop more effective strategies by understanding how they use space and why they avoid certain areas. This means not just protecting patches of forest but also ensuring that the canopy is connected, allowing these arboreal experts to move safely, and reducing disturbances, especially near forest edges where human activity is higher. It's a reminder that protecting wildlife isn't just about saving a single species; it's about safeguarding the intricate, multi-dimensional natural world we all depend on.
Based on a Press Release by Centre for Wildlife Studies (CWS)