Ratha Sor pauses beneath the emerald canopy of the Cardamom Mountains, ear pressed to a speaker playing a high-pitched, cascading call that echoes through the treetops— the song of the pileated gibbon, a haunting melody now captured by hidden microphones deep in Cambodia’s largest intact rainforest. For Sor, biodiversity and science manager at Conservation International (CI), each note is more than sound; it’s proof that this vast wilderness, spanning over 1 million hectares in southwest Cambodia, still pulses with life. After decades of deforestation and poaching emptied these forests, new technology is revealing a resurgence of wildlife, from elephants to pangolins, and offering a fighting chance for their survival. In 2024, CI published findings from the first systematic camera trap survey of the Central Cardamom Mountains, documenting over 100 species—24 of them vulnerable or endangered—thanks to nearly 150 strategically placed devices. Among the rare sightings: pig-tailed macaques, dholes (endangered wild dogs), and elephants, a species so elusive that one ranger reported not seeing a single individual in 12 years of patrols. Local knowledge has been vital; Chong Indigenous community member Pan Sok, a 50-year-old resin tapper known as a “jungle man,” helped place cameras and beams with pride at the footage they’ve captured. “My efforts paid off,” he said, watching elephants move gracefully through the underbrush. But some animals, like the canopy-dwelling gibbons, evade even the most advanced camera traps. To find them, CI turned to bioacoustic monitoring and artificial intelligence. Dozens of audio recorders, spaced at least 3 kilometers apart to capture distinct gibbon troops, collected nearly 800 calls in just six weeks. Scientists spent three months training an AI model to distinguish gibbon calls from other forest noise—a process Sor describes as teaching the system “this is gibbon, this is not.” The AI now processes thousands of hours of audio, with plans to eventually identify individual animals by their calls. Despite progress, threats remain. Infrastructure projects, especially dams, continue to drive deforestation. In the past five years alone, the Central Cardamom protected area lost nearly 7,000 hectares of tree cover, according to Global Forest Watch. Yet the symphony of life captured by hidden ears in the forest offers a powerful counter-narrative: this ecosystem is not lost. With technology and tradition working in tandem, the Cardamoms may yet remain a sanctuary for generations to come.