whose entourage grows throughout the day. 它们的活动忙碌一整天

153. to graze on the vegetation below.
     再吃下面的植物
154. The ice-breakers create an opening for other over-winterers.
     麝牛破冰也为其它越冬的动物创造机会
155. Flocks of ptarmigan make unusual grazing companions for the musk oxen,
     成群的雷鸟与麝牛结成了紧密的伙伴关系
156. whose entourage grows throughout the day.
     它们的活动忙碌一整天
157. This odd assembly of vegetarians doesn't go unnoticed.
     这些食草动物组成的奇特群落当然会引起注意
158. An arctic fox.
     一头北极狐
159. The musk oxen have recently given birth.
     麝牛最近生了幼仔

来自《行星地球 第一季 第六集 Planet Earth S01E06 冰雪世界》第 156 行