July 29th is Global Tiger Day, an annual day to celebrate the tiger and to raise awareness for the approximately 3,900 wild tigers left in the world today. Found primarily in the rain forests, grasslands, and savannas of Asia, wild tiger populations have dropped 97% over the last hundred years, making tigers an endangered species. During the Vietnam War era, however, the Indochinese tiger population was healthy and thriving, providing the CIA a creative way to covertly track the movement of the Northern Vietnamese and Viet Cong.

Starting in 1955, the Vietnam War was a decades-long conflict between the communist government of North Vietnam and the government of South Vietnam. Considered a proxy of the Cold War, the North Vietnamese army was supported by communist allies like the Soviet Union and China, while the South Vietnamese army was supported by the United States, South Korea, and other anti-communist allies.

During the war, the US needed a way to monitor the opposition’s location and movement, which was instrumental in strategic planning.

That’s where tigers came in.

CIA technologists invented what is known as the seismic intruder detection device. It could be strategically placed to monitor movements up to 300 meters away. However, our scientists had to disguise the technology as an object that would blend into the natural habitat, while at the same time repel interest. Since tigers are native to Vietnam and were found in larger numbers 50 years ago, they provided the ideal cover.

The detection device was designed to look like tiger droppings.

Seismic intruder detection device. Photo by CIA Museum.

Fueled by tiny power cells and containing a built-in antennae, the device was only 10.3 cm in length and 2 cm in diameter. It tracked movement by detecting and counting vibrations made by passing people, vehicles, and animals. Transmitters would then relay the data from the device via coded impulses. By disguising the device to look like tiger scat, it blended in with the natural landscape and was highly unlikely to draw attention.

Today, we continue to develop creative technical collection systems to further US national security objectives. Whether it’s a reconnaissance satellite circling the earth, invisible ink concealing coded messages, or a seismic intruder detection device hidden inside faux tiger droppings. Throughout history, CIA has always utilized cutting-edge technology to tackle the nation’s hardest intelligence challenges.