Abstract
Bats are renowned for their use of echolocation, but recent research has suggested that hoary bats (Lasiurus cinereus) may fly without their highly specialized sensory ability. To test the hypothesis that hoary bats fly without echolocation, we attached miniature (2.7 g) tags that record ultrasound and accelerations to 10 wild hoary bats and later recovered them using aerial and ground based radio telemetry. This resulted in over 2000 10-second recordings made over one or two nights per bat. We confirmed that hoary bats fly without using echolocation for extended periods of time lasting up to 20-30 minutes. This is the strongest evidence to date that bats are not reliant on echolocation for nocturnal navigation. We use acceleration and acoustic data to better understand these behaviors and propose that turning off echolocation serves to avoid eavesdropping from potential mates and competitors. These results also have implications for protecting hoary bats from wind turbines, which kill tens of thousands of hoary bats every year.