Creating a Sanctuary: Protecting Snails and Restoring Ecosystems at War in the Pacific National Historical Park

By Christina Martin, I&M Research Scientist and Communication Specialist
March 2025

In the hushed stillness of the jungle, a sharp ki-ki-ki pierces the air—the call of a Guam rail. Once a familiar sound, it is now a rare echo of the past. The lush landscapes of War in the Pacific National Historical Park (NHP) were once alive with the vibrant calls of native wildlife. But today, the island has fallen eerily quiet in comparison. Invasive species, habitat loss, and extreme weather have disrupted the ecosystem, causing many of its voices to vanish from Guam entirely.

One of the species most affected by these disruptions is the endangered Guam tree snail (Partula radiolata). Though small and often overlooked, these snails play a vital role in nutrient cycling by breaking down organic matter. Without intervention, the loss of biodiversity—including the decline of tree snails—could continue to unravel Guam’s fragile ecosystem. Given these challenges, researchers and park managers are taking action to protect what remains and restore what has been lost.

Two Guam tree snails slowly make their way up a tree trunk, playing their vital role in the island’s ecosystem.

NPS

Managing Invasive Species While Protecting Native Wildlife

War in the Pacific NHP is committed to restoring Guam’s ecosystems by controlling invasive species while safeguarding native wildlife. Two of the most significant threats to the island’s ecological balance are brown tree snakes (Boiga irregularis) and little fire ants (Wasmannia auropunctata). Brown tree snakes have devastated Guam’s native bird populations, leading to disruptions in pollination and seed dispersal. Little fire ants pose another serious threat, forming dense colonies that endanger other invertebrates by preying on them or outcompeting them for resources. Removing these invasive species is crucial to preserving the island’s biodiversity.

Because invasive species removal often takes place in areas where tree snails live, the park staff take extra precautions to minimize unintended harm. As traps are fastened to branches and teams move through the forest to capture brown tree snakes, delicate tree snails—clinging to leaves and bark—risk being knocked loose, trampled underfoot, or displaced from their habitats. Protecting vulnerable species like the Guam tree snail requires thoughtful planning to ensure conservation efforts do not inadvertently put them at risk.

A Study to Inform Conservation Strategies

To develop more effective conservation plans, researchers set out to assess the remaining population of Guam tree snails. They also aimed to identify ways to protect the snails during invasive species removal and understand the potential impact of little fire ants on their survival.

In April 2023, the National Park Service’s Inventory and Monitoring Division launched a Guam tree snail study in the park’s Asan Ridge unit.

A Guam tree snail rests beside a fingertip, highlighting its small size.

NPS

Led by Dr. Ann Marie Gawel, a Postdoctoral Research Associate at the State University of New York College of Environmental Science and Forestry, the study involved meticulously surveying 48 transects across 15 acres. Gawel scanned leaves, branches, and even high canopy areas for the small snails, recording their age and the type of plant they were found on. By the end of the surveys, she had created a detailed snapshot of the Guam tree snail population, providing critical information to guide conservation efforts. But just as the study was wrapping up, an unexpected challenge arose—one that would test the resilience of these tiny creatures.

In May 2023, Typhoon Mawar swept across Guam, unleashing fierce winds that stripped trees of their leaves and damaged large portions of the forest. While destructive, the storm provided a rare opportunity to study how extreme weather impacts tree snails. Using the same transects, Gawel conducted post-typhoon surveys in June to compare populations before and after the storm.

Side-by-side images of Asan Ridge before and after Typhoon Mawar, revealing the dramatic loss of vegetation caused by the storm.

NPS

Results: Resilience Amid Challenges

Despite significant habitat damage, the Guam tree snails showed surprising resilience. Before the typhoon, Gawel recorded 225 snails. Afterward, she found 177. The biggest loss was among juveniles, whose numbers dropped by nearly 80%, but the adolescent and adult snails remained relatively stable. This suggests that while young snails are more vulnerable, the species as a whole can withstand harsh conditions.

Even after the typhoon left Asan Ridge looking barren, the tree snails endured. As long as we maintain the critical habitat they depend on, they can survive even the most devastating challenges.

—Timothy Clark, Natural and Cultural Resource Manager,   War in the Pacific NHP

Researchers also found that while fire ants were present in Guam tree snail habitats, they hadn’t yet caused noticeable harm to the snails. However, this could change if fire ant numbers increase, reinforcing the need for ongoing monitoring.

Improving Conservation Practices

The findings from this study have already influenced conservation strategies at War in the Pacific NHP. Areas with dense tree snail populations are now carefully avoided during brown tree snake removal activities. Before clearing vegetation to access brown tree snakes, staff check for snails and, if found, either relocate them to safer areas or leave them on cut branches so they can move to new trees.

This study also highlighted the importance of controlling fire ants. Knowing that ants and snails coexist in some areas has emphasized the need for continued monitoring and intervention to prevent ant populations from reaching destructive levels. Managing fire ant populations will not only help prevent harm to tree snails, but also protect visitors and staff from their painful stings.

Looking Ahead: A Future for Guam’s Native Wildlife

By protecting habitats and minimizing disturbances, War in the Pacific NHP is working to restore Guam’s ecosystems and create a sanctuary for native species. Preserving biodiversity while managing invasive threats is an ongoing challenge, but the resilience of species like the Guam tree snail offers hope. While the island’s ecosystems have been forever changed, conservation efforts can help native species recover. With time and dedication, Guam’s forests can once again provide a thriving refuge for the life that makes this place unique.

A sweeping view of War in the Pacific National Historical Park, showcasing the lush limestone forests that provide critical habitat for Guam’s native species.

NPS

Want to learn more?

Explore other species found in War in the Pacific NHP on NPSpecies, or learn about additional projects through the Pacific Island Inventory & Monitoring Network (U.S. National Park Service).