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The mainpurpose of the passage is to?
This passage is adapted fromLynne Peeples “Moths Use Sonar-Jamming Defense to Fend Off Hunting Bats.” ©2009 by Scientific American
Aninsect with paper-thin wings may carry much the
same defense technology as some of themilitary's heavy-
duty warships. The finding that a species oftiger moth can
jam the sonar of echolocating bats to avoidbeing eaten
seems to be the "first conclusive evidenceof sonar jamming
in nature," says Aaron Corcoran, a biologyPhD student at
Wake Forest University and the lead author ofthe paper
reporting the discovery. "It demonstratesa new level of
escalation in the bat–moth evolutionary armsrace."
Before Corcoran's study, scientists werepuzzled by why
certain species of tiger moths made sound. Somespeculated
that the moths use it to startle bats. A fewpointed to its
potential interference with their echolocation.General
consensus, however, fell with a thirdhypothesis: clicks
function to warn a predator not to eat theclicking prey
because it is toxic, or at least pretending tobe.
To test these hypotheses, Corcoran and his teampitted
the tiger moth Bertholdia trigona against the big brown
bat Eptesicusfuscus, a battle frequently fought after
sundown from Central America to Colorado.High-speed
infrared cameras and an ultrasonic microphonerecorded the
action over nine consecutive nights. Theprocess of
elimination began. If moth clicks served tostartle, previous
studies suggested the bats should becometolerant of the
sound within two or three days. "Butthat's not what we
found," says Corcoran, explaining the lackof success bats
had in capturing their clicking prey eventhrough the last
nights of the study.
How about the toxic warning theory? If thiswere the
case, according to Corcoran, bats would notfind the
moths palatable or, if they were indeed tasty,they would
quickly learn they'd been tricked. Either way,bats should
start to ignore the moth's unique ultrasonicclicks. Also, bats
partook readily when offered B. trigona that lacked the
ability to click, and they kept coming back formore. This
attraction also held true for clicking B. trigona: The
predators persisted after their prey despiteonly reachinghem about 20 percent of the time. Bats actually launched
four times as many successful attacks against acontrol group
of silent moths. These findings are "onlyconsistent with the
jamming hypothesis," Corcoran notes."But the most
distinctive evidence was in the echolocationsequences of the
Normally, a bat attack starts with relativelyintermittent
sounds. They then increase in frequency—up to200 cries per
second—as the bat gets closer to the moth"so it knows
where the moth is at that criticalmoment," Corcoran
explains. But his research showed that just asbats were
increasing their click frequency, moths"turn on sound
production full blast," clicking at a rateof up to 4,500 times a
second. This furious clicking by the mothsreversed the bats'
pattern—the frequency of bat sonar decreased,rather than
increased, as it approached its prey,suggesting that it lost its
The biological mechanism behind the moth'sdefense
strategy is still unclear to researchers."Most likely, moth
clicks are disrupting the bat's neuralprocessing of when
echoes return," Corcoran says. Bats judgehow far away a
moth is based on the time delay between makingthe cry and
its audible return. This "blurring"of the bat's vision, he
explains, "may be just enough to keep themoth safe."
The passage is primarily concernedwith
(A) the ways Eptesicus fuscus bats capture moths.
(B) the discovery that tiger moths can jambats’ sonar.
(C) how the tiger moths’ clicking defenseworks.
(D) why tiger moths developed defenses againstbats.