The sea ice still holds firm, 海面上的冰层依然坚固

53. But their mother must keep them out and active.
    可是母熊必须得把它们带到外边活动
54. She's becoming weak from hunger
    饥饿将它折磨得虚弱不堪
55. and there's no food on these nursery slopes.
    而这片产仔的斜坡上没有一点食物
56. The sea ice still holds firm,
    海面上的冰层依然坚固
57. but it won't last much longer.
    但是这种情况不会持续太久
58. Day 10,
    第10天
59. and the mother has led her cubs a mile from the den.
    母熊已经带领幼熊离巢1英里远

来自《行星地球 第一季 第一集 Planet Earth S01E01 从北极到南极》第 56 行