Stereotyped active sensing in fast-diving echolocating bats

Mexican free-tailed bats (Tadarida brasiliensis) often return to their roosts in darkness or low-light conditions from high altitudes (> 3 km) in steep, fast dives. We recorded 26 bats as they performed reentry dives to their canyon roost in New Mexico shortly after dawn and analyzed their sensorimotor behaviors. We tracked bats at altitudes up to 25.6 meters from the ground surface; bats dove at maximum speeds of 22.1 m/s (82.1 km/h), experienced up to 9.2 g forces, and traversed up to 6 meters (∼60 body lengths) between receiving echoes from the ground. Bats adjusted their echolocation in a stereotyped pattern once the ground was within detection range by decreasing signal duration, decreasing interpulse intervals, and increasing signal end frequency. Analyses suggest bats receive relatively sparse echo information during dives and likely integrate this information with cognitive spatial maps and available visual cues to safely complete their high-speed roost reentry.