In Britain, a Liverpudlian can have trouble understanding a Geordie accent from Newcastle, and a posh north Londoner can sound nothing like an East Ender living just a few kilometres away. But regional accents don't just exist in humans. Australian scientists have discovered the same situation exists in bats. "Bats in different regions have different calls. You may have the same species on the north and the south coast but they'll have different calls," said research leader Brad Law, of the Forest Science Centre, which is part of Industry and Investment NSW. Scientists had long suspected bats had distinctive regional dialects, but it had never been proven in the field, Dr Law said. As part of their research, the team spent months capturing bats at night, identifying each one and recording their calls with special equipment. Bats use their calls to navigate and hunt, a process called echolocation. They produce high frequency ultrasounds, which cannot be heard by humans, that hit objects as they are flying along and echo back. "They are able to form an image of their world from sound" said Dr Law. The team recorded 4,000 calls from about 30 species of bat in New South Wales. To identify one species' call from another they developed an automated identification key based on the bats living in a specific region. "When we go out in the forest, we can record thousands of calls a night, all of which are unknown," Dr Law said. "If we weren't able to run them through the automated key, it could take months to identify them." The researchers developed an identification key for each region. Why there are regional call differences is still unknown, but Dr Law suspects it may have something to do with their diet because bats use their calls to locate food. "Some bats feed on tiny mosquitoes which means they use a very high frequency call [to locate them], while others feed on beetles or big moths and use a lower frequency call." The researchers now use their call identification process to survey bats across the state. The surveys will help them identify any endangered bat species.