but they nonetheless need a regular supply of water. 但它们仍须定期补充水

133. you'd expect the place to be completely barren.
     不难想象这个地方定是彻底的荒芜
134. These are South America's camels, guanacos.
     这些是南美洲的骆驼——原驼
135. They're very good at conserving moisture
     它们非常善于保存水分
136. but they nonetheless need a regular supply of water.
     但它们仍须定期补充水
137. They get it partly from cactus flowers
     其中一部分水取自仙人掌花
138. but that explanation raises another question.
     但这里又牵扯出另一个问题
139. How do the cacti survive without rain?
     仙人掌为何能在这个无雨地带生存

来自《行星地球 第一季 第五集 Planet Earth S01E05 沙漠》第 136 行