How do tiger moths jam bat sonar?

Abstract

SUMMARYThe tiger moth Bertholdia trigona is the only animal in nature known to defend itself by jamming the sonar of its predators -bats. In this study we analyzed the three-dimensional flight paths and echolocation behavior of big brown bats (Eptesicus fuscus) attacking B. trigona in a flight room over seven consecutive nights to determine the acoustic mechanism of the sonar-jamming defense. Three mechanisms have been proposed: (1) the phantom echo hypothesis, which states that bats misinterpret moth clicks as echoes; (2) the ranging interference hypothesis, which states that moth clicks degrade the bats' precision in determining target distance; and (3) the masking hypothesis, which states that moth clicks mask the moth echoes entirely, making the moth temporarily invisible. On nights one and two of the experiment, the bats appeared startled by the clicks; however, on nights three through seven, the bats frequently missed their prey by a distance predicted by the ranging interference hypothesis (~15-20cm). Three-dimensional simulations show that bats did not avoid phantom targets, and the bats' ability to track clicking prey contradicts the predictions of the masking hypothesis. The moth clicks also forced the bats to reverse their stereotyped pattern of echolocation emissions during attack, even while bats continued pursuit of the moths. This likely further hinders the bats' ability to track prey. These results have implications for the evolution of sonar jamming in tiger moths, and we suggest evolutionary pathways by which sonar jamming may have evolved from other tiger moth defense mechanisms. Supplementary material available online at

Sonar jamming in the field: effectiveness and behavior of a unique prey defense

“…Depending on whether a species is chemically defended and the amount of sound it produces, moth clicks serve as acoustic aposematic (Hristov and Conner, 2005a;Hristov and Conner, 2005b;Ratcliffe and Fullard, 2005), mimetic (Barber and Conner, 2007;Barber et al, 2009) or sonar-jamming signals (Corcoran et al, 2009;Corcoran et al, 2010;Corcoran et al, 2011;Conner and Corcoran, 2012). In some cases these defenses may be combined; for example, a small degree of sonar jamming may enhance bat learning of aposematic signals (Ratcliffe and Fullard, 2005).…”

“…These clicks then disrupt the timing of the firing of bat auditory neurons that are involved in encoding target distance (Tougaard et al, 1998). The number of clicks that fall within this window determines the size of ranging errors (Miller, 1991) and the likelihood of bat capture (Corcoran et al, 2011). In captivity, jammed bats narrowly miss their prey by a distance predicted by psychophysical studies (Corcoran et al, 2011).…”

Tempo and mode of antibat ultrasound production and sonar jamming in the diverse hawkmoth radiation

“…The sounds that these moths make can startle bats (11), warn them of bad taste (12,13), and jam bat sonar (14)(15)(16). Jamming likely functions to confuse the bat because it interferes with the bat's perception of its own echoes that are reflecting off of its prey (16,17). The evolution of moth antibat ultrasound production is thought to have originated from simple warning sounds and developed into complex signals that jam bat sonar (14).…”

Defense through sensory inactivation: sea hare ink reduces sensory and motor responses of spiny lobsters to food odors

“…The mechanism underlying this jamming is not inactivation of the bats' periphery auditory system, as bats can detect their ultrasonic echoes bouncing off moths. Rather, the moths' ultrasound interferes with the ability of the bats' central nervous system to calculate correctly the distance of the moth (Corcoran et al, 2011). Other moth species use their ultrasound as an aposematic defense, or as Batesian or Müllerian mimics, rather than for jamming (Hristov and Conner, 2005a;Hristov and Conner, 2005b;Conner and Corcoran, 2012).…”