Bats, as the main predator of night-flying insects, have led many of their prey to evolve an early warning system, with at least six orders of insects evolving ears capable of detecting ultrasound. Tiger beetles, in particular, respond to bats nearby with their own ultrasonic signal, a behavior that has puzzled scientists for the past 30 years. Researchers led by Harlan Gough recently conducted a study that finally solves this mystery. Tiger beetles seem to receive a major benefit from making this sound, as it also helps bats locate them. The study found that tiger beetles are the only group of beetles known to produce ultrasound in response to bat predation.
The researchers confirmed that tiger beetles produced ultrasound in response to bat predation, as bats use ultrasonic pulses to locate their prey in the dark. The elytra of the tiger beetles would swing slightly towards the back in response to the bat echolocation attack sequence, causing the beating hind wings to strike the back edges of the elytra, creating a buzzing sound that bats can hear. While this behavior may seem strange, it is a common ability in moths, with an estimated 20% of moth species capable of producing ultrasound in response to bat predation.
The researchers initially suspected that tiger beetles were using ultrasound to warn bats of their defensive chemicals, such as benzaldehyde and hydrogen cyanide, but experiments showed that this was not the case. Instead, they discovered that tiger beetles produce ultrasound to mimic tiger moths, which are noxious to bats. This behavior is limited to tiger beetles that fly at night, as diurnal tiger beetles that are active during the day do not have the same selective pressure of bat predation. This discovery sheds light on the delicate ecological interactions that take place in the night sky and the need to protect these interactions from human impacts like noise and light pollution.
The researchers believe that there may be more undiscovered examples of ultrasonic mimicry in nocturnal insects, as the acoustics of the night sky remain largely understudied. Acoustic mimicry requires a quiet environment to work effectively, but human impacts like noise and light pollution are already altering the natural soundscape of the night sky. Understanding these ecological processes is crucial, as disruptions in these delicate interactions can have far-reaching consequences on biodiversity and ecosystem health.
The study, published in the journal Biology Letters, was co-authored by Juliette Rubin, a former graduate student at the University of Florida, and Jesse Barber of Boise State University. The researchers hope that their findings will contribute to a better understanding of the intricate relationships between predators and prey in the natural world. By studying these processes now, we can gain insights into the complex mechanisms that drive ecological interactions and work towards preserving the delicate balance of our natural ecosystems.