Just as no two people have the same set of fingerprints, no two tigers have the same pattern of stripes. This distinguishing feature has long been employed by conservationists working in the field using camera traps to count just how many of the big cats roam an area, but this may not be the only way that tigers show their individuality. It seems that the cats may also be calling to their own tune.

By using recordings of captive tigers across different collections in the United States, The Prusten Project has revealed that the tigers' calls are unique to the individual and so can be used to identify them. The cats make a few different types of noises, from long roars in order to find mates, to short roars for intimidation, to bizarre snorting or chuffing noises, also known as “prusten”. Using a computer program to analyze their roars for frequency and duration, among other characteristics, the researchers can make pretty accurate estimates of who is making what sounds.

The project, which is funded by the American Association of Zookeepers, has added more tigers to its database by recording the calls of four of the big cats kept at the Milwaukee Country Zoo, in order to help expand their knowledge of the difference in noises between tiger subspecies. The team have already sent recorders out to Sumatra to listen to one of the rarest types of the big cat, with plans to extend it to India.

The use of sound in biology, termed bioacoustics, has long been used by marine biologists to tap into the conversations of whales, and has even been used by those in the rainforests of central Africa to eavesdrop on forest elephants. The large animals travel vast distances through the thick and often impenetrable forests, making them difficult to track, yet they stay in contact with each other by sending out low-frequency rumblings. It is these that can be tapped into, allowing researchers at the Elephant Listening Project to not only tell how many elephants might be hidden out there in the forest, but also what they’re up to.

Yet those microphones stationed in the rainforests have also been able to pick up on more sinister activity. Researchers have identified illegal poaching and logging in the regions as the sounds of chainsaws and gunshots echo through the trees. With poaching and deforestation also major threats to the survival of tigers in the wild, those over at The Prusten Project hope their program can help determine population numbers in the wild so that organizations can better choose where to focus their protection efforts.