There is simply not enough prey to sustain more. 只是因为猎物数量不足以维系更多的生命

274. we are getting closer to them than ever before.
     我们终于能够近距离观察他们
275. They are very rare,
     雪豹数量稀少
276. only about four of them in 40 square miles.
     百平方公里内只有四只
277. There is simply not enough prey to sustain more.
     只是因为猎物数量不足以维系更多的生命
278. They live solitary lives.
     雪豹是独居动物
279. Nonetheless, they are well aware of the presence
     尽管如此 他们仍能很好地掌握
280. and the movements of their neighbours,
     邻居们的存在和动向

来自《行星地球 第二季 第二集 Planet Earth S02E02 山脉》第 277 行