Giant pandas have better ears than people — and polar bears. Researchers found out that pandas can ＿＿（41）＿＿ surprisingly high frequencies. The scientists played a range of tones for five zoo pandas trained to ＿＿（42）＿＿ a target in response to sound. Training took three to six months for each animal and ＿＿（43）＿＿ serious focus and patience, which, according to an expert, was “a lot to ask of a bear.” Both males and females heard into the range of a “silent” ultrasonic dog whistle. Polar bears, the only other bears scientists have tested, are ＿＿（44）＿＿ sensitive to sounds at or above 14 kilohertz. Researchers still don’t know why pandas have ultrasonic hearing. The bears are a ＿＿（45）＿＿ bunch, but their chirps and other calls have never been recorded at ultrasonic levels. Great hearing may be a holdover from the bears’ ancient past.