Submitted to: North American Symposium on Bat Research
Publication Type: Proceedings
Publication Acceptance Date: 11/4/2002
Publication Date: N/A
Technical Abstract: Many insects, including many agricultural pests, respond to the ultrasonic calls of bats by taking evasive action and curtailing flight activity. Earlier attempts to exploit this co-evolved relationship to inhibit insect activity for crop protection (Belton and Kempster 1962) showed promise, but were not pursued due to observations that the insects quickly habituated to the monotonous artificial ultrasonic pulses that were used in that study. Also, we now know that bats which forage in groups are attracted to the feeding calls of other bats, leading to enhanced foraging activity in areas where other bats are actively feeding. We have developed "virtual bats," electronic pulse simulators that are programmable to emit continuously varying arrays of ultrasonic pulses that closely mimic the complexity of search, approach, and feeding calls of real bats. Virtual bats programmed to mimic the calls of Mexican free-tailed bats (Tadarida brasiliensis mexicana) were field-tested in experimental (virtual bat present) and control plots (no virtual bat) in large fields of corn and cotton in South Central Texas, at a site ca. 7 miles from Frio Cave, seasonal home to several million Mexican free-tailed bats. Experiments were conducted during the time that corn earworm moths (Helicoverpa zea: Noctuidae) emerge in large numbers from senescent corn and infest fruiting cotton. Moth flight activity monitored using infrared (IR) video at the center of each plot was 27% lower in the experimental plot of corn and 37% less in the experimental plot of cotton than in the respective control plots of each crop type. IR video counts of bat passes were 18 times higher in the experimental cotton plot and 119 times higher in the experimental corn plot than counts in the respective control plots. Bat foraging activity measured as the total numbers of echolocation pulses recorded by bat detectors in the center of each plot were almost three times greater in the corn experimental plot and over two times greater in the cotton experimental plot than in the respective control plots of each crop type. This research documents the effects of the variable pulses emitted by virtual bats, both in reducing moth flight activity and enhancing bat foraging activity over crops. Data analysis will be expanded by the time this paper is presented. On-going research is evaluating the agronomic potential of virtual bats as an application for environmentally benign crop protection. Extension of this application for use with other bat assemblages, and for use in high-value row and orchard crops will be considered.