英语听力：自然百科 黄石公园的夏天 Yellowstone—18（在线收听） |
But just as the first of Yellowstone's new generation are preparing to leave, its last visitors are arriving. Night after night, army cutworm moths have been escaping the heat of a distant prairie. They have been flying in on favorable winds, hiding away in / rock crevices in the mountains. This is why the grizzly bears climb to the barren peaks. Two miles up, they / begin to search for the moths. It is the end of summer, and the last snow of winter holds on only here. It offers a few refreshing mouthfuls for travel-weary cubs.
Many of these bears learnt about this site from their mothers, as a part of local bear tradition. The family sets to work, finding moths, digging into the loose rock.
Though each moth is very small, a bear that makes a successful strike can harvest up to 40,000 in a single day, that is 20,000 calories and vital weight gained for winter.
Having spent all summer avoiding males, the mother now finds one much too close for comfort. Perhaps she is seeking a mate, but he is unwelcome. Leaving her cubs, she confronts the male head-on.
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