Heart rate tracking for three of the Alaska bears showed a drop from 55 beats per minute on average before hibernation to 14 erratic ones per minute in winter.
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根据世界自然基金会表示，全球的黑犀牛数量已下降至5500头，使犀牛处于“极度濒危”状态。
According to the World Wildlife Fund, the global black rhino population has dropped as low as 5500, giving the rhinos a "critically endangered" status.
The slaughter was so "effective" that the population of bison in the U.S. is estimated to have dropped from around 60 million in 1800 to as few as 750 in 1890.
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