African elephants (Loxodonta africana) communicate using low-frequency acoustic vocalizations known as “rumbles,” which can propagate through savannah environments across several kilometers. Behavioral ecologist Karen McComb and colleagues recorded elephant rumbles and tested how listeners distinguish familiar herd members from unfamiliar conspecifics. While earlier models assumed that low-frequency fundamental tones below 20 Hz (infrasound) carry individual vocal signatures over maximum distances, McComb discovered that acoustic recognition of specific herd members degrades significantly at distances exceeding 1.5 kilometers, because higher-frequency vocal tract resonances (formants) around 115 Hz attenuate and become obscured by ambient environmental noise. McComb therefore concluded that
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Verbal·Information and Ideas·Inferences
easyWhich choice most logically completes the text?
A
infrasonic frequencies below 20 Hz are solely responsible for coding the individual social identity of calling elephants.
B
long-distance social recognition in elephants depends on specific acoustic formant frequencies whose effective transmission range is narrower than the overall audible range of elephant infrasound.
C
ambient environmental noise enhances the propagation speed of low-frequency elephant contact rumbles across open savannah landscapes.
D
female African elephants cannot differentiate between the vocal calls of family members and unfamiliar elephants at any distance.