The Effectiveness Of Moth Acoustic Defenses Against Horseshoe Bats

Predator–prey interactions are one of the most important interactions between species in ecological communities,and the anti-predator behaviors of prey can influence the population dynamics of prey–predator systems.The "acoustic arms race" between bats and moths is a classic example of predator-prey interactions.Although moths have evolved a suite of acoustic defenses,for example,ultrasound production,against predation by low-duty-cycle bats.However,High-duty-cycle bats such as the horseshoe bats prey on moths in large numbers.There is a lack of research on the effectiveness of moths’ anti-predation strategies to defend against predation by high-duty-cycle bats,and the differences in the effectiveness of hearing and ultrasound anti-predation strategies and their mechanisms are largely unknown.It is difficult to study bat–moth interactions directly in nature.Behaviorists typically use laboratory behavioral experiments to address this challenge.Whether the behavioral results of bat-moth interactions observed under laboratory conditions can actually reflect their interactions in the wild remains unknown.To address the above questions,this thesis takes the example of horseshoe bats and moths.this thesis investigates the effectiveness of the moth’s hearing and ultrasonic antipredation strategy for defense against high-duty-cycle bats and its mechanism,and tests whether the effectiveness of the moth’s anti-predation strategy(capture success of bats)under indoor behavioral experiments can directly predict the outcome of the interaction between bats and moths in the field(diets composition of bats),with the following main results:(1)We investigated the success rate of Rhinolophus episcopus and Rhinolophus osgoodi capturing earless moths,non-click eared moths,and anti-bat-click moths in flight in a recording room.The horseshoe bats had a low success rate when capturing clicking moths but had a high success rate when capturing those without an acoustic response.(R.episcopus:16% vs 66% vs 62%;R.osgoodi: 12% vs 73% vs 60%),and their success in preying on eared moths was not significantly different from that of earless moths.(2)Analysis of bat predation using DNA metabarcoding techniques showed that horseshoe bats predominantly prey on eared moths(R.episcopus: 84%-91%;R.osgoodi:68%-79%).(3)Moth diversity in bat foraging habitats was investigated by light trapping,and behavioral experiments were used to clarify whether moths have anti-predatory ultrasound.Combining morphological and genetic data to identify moths captured in bat foraging habitats revealed 7 species of earless moths,34 species of non-click eared moths and 13 species of anti-bat-click moths,with 8.7%(n = 80),34.3%(n = 315)and 35.1%(n = 322)of individuals,respectively.There was no significant difference in the percentage of individuals between eared moths and anti-bat-click moths,both of which were significantly higher than the percentage of moths without hearing.20 earless moths species,one eared moth species and one anti-bat-click moth species were preyed upon by the R.episcopus and R.osgoodi.Nonclick eared moths(58.8%)accounted for a higher proportion of bat predation than earless moths(14.3%)and anti-bat-click moths(15.4%).(4)The ultrasonic responses and palatability of Cechenena minor and Creatonotos transiens were studied when they were predated by flight R.osgoodi.The C.minor and C.transiens produced ultrasonic clicks with an average high duty cycle of 67% and 44%,respectively.The ultrasound of the C.minor overlapped spectrally with the echolocation of the R.osgoodi,and the C.transiens occasionally emitted ultrasound immediately after the end of the feeding buzz of the bat.The clicks of C.transiens did not overlap spectrally with the echolocation calls of R.osgoodi.In most cases,the click of the C.transiens was produced prior to the appearance of the feeding buzz.In addition,C.minor were palatable and C.transiens were unpalatable to R.osgoodi.In summary,the results of both behavioral experiments and diets analyses suggest that moth ultrasound is an efficient predation strategy,and that hearing is not an efficient defense against predation by horseshoe bats.Moth ultrasound may have the function of interfering with the echolocation of the horseshoe bats or advertising moth toxicity,thus defending against high-duty-cycle bats predation.Results on the effectiveness of moth antipredation strategies obtained from indoor behavioral experiments do not necessarily accurately predict the diets composition of bats in the wild.The latter depends not only on the moth’s antipredation strategy,but is also influenced by the predation response of bats and the availability of moth resources.In this paper,we investigate the behavioral effectiveness of two of the most prevalent anti-predation acoustic strategies,moth hearing and ultrasound,in defending against highduty-cycle bats predation,and explore the possible mechanisms of moth ultrasound defense against high-duty-cycle bats predation,contributing to insight into the bat–moth "arms race" and its evolution.In addition,This study illustrates the importance of using a combination of behavioral experiments and molecular genetic techniques to reveal the complex interactions between predators and prey in nature.