Toothed whales echolocate by creating a series of clicks emitted at various frequencies. Hipposiderid bats echolocate with combined CF/ FM-sounds at 127-138 kHz. This indicates that early bats could fly before they could echolocate. Individual bat species echolocate within specific frequency ranges that suit their environment and prey types. To echolocate, they produce sound through their nostrils. Flying foxes do not echolocate, and therefore rely on sight to navigate. This fusion is associated with the ability to echolocate while stationary. They navigate with keen eyesight, as they cannot echolocate. A few other megabat species echolocate via creating clicks with their wings. The bat's strong sense of hearing allows them to echolocate. It appears not to rely on its hearing to find insects and does not echolocate.