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Small, tasty mammals like dwarf¹ mongooses have one main goal: do not get eaten. So the animal—a type of weasel—has a surveillance system. While most of the group focuses on finding food, a handful of others watch for predators². They take turns so that the burden is distributed equally. But in other ways, there’s a definite class distinction.

体型小又美味的哺乳动物---猫鼬有一个主要目标：不要被吃掉。所以这种动物——它一种黄鼠狼——有一个监视系统。虽然猫鼬大部分工作重点是寻找食物，但其他一小部分猫鼬则监视食肉动物的捕猎活动。它们会轮流值班使负担平均分配。但是在其他方面，它们还有明确的等级差别。

"You have a typical cooperative breeding society, which you see in a number of different species, like meerkats for example or African wild dogs. So you have a dominant³ breeding pair, male and female pair that will reproduce, and they're the only group members that are guaranteed to have offspring."University of Bristol biologist Julie Kern.

“你有一个典型的合作型繁殖社会，可以看到许多不同的物种，比如猫鼬或者非洲野狗，所以有一个优势的育种配对对象，雌雄配对，它们是唯一可以保证有优良后代的小组成员。“布里斯托大学生物学家Julie Kern说。

"But then within both sexes there's a linear dominance hierarchy⁴, so if you are quite far down the hierarchy in your own group, it could take quite a long time for you to reach that breeding position, which is what you really want. So it may be best for you to actually leave your group that you were born into and try to join another group where there are fewer same sex individuals, so you can effectively join a group higher up the queue than the one that you're already in."When new immigrants shows up, that means more mongooses can act as lookout⁵ against predators. Right? In reality, it’s more complicated.

“但是在两性中都有一个线性的支配等级，所以，如果在自己的群体中的等级很低，那么你需要相当长的时间，才能达到繁殖的位置，而这是你真正想要的。可能你要离开自己出生的小组，并尝试加入同一性别较少的另一个小组，因此你可以有效地加入其它队伍中，而不是你已经在队伍中的小组。“当新入伙的猫鼬出现时，这意味着会有更多的猫鼬，可以充当掠食者的角色。事实上，这更加复杂。

Kern and her team observed seven different groups of wild dwarf mongooses in South Africa. They found that new immigrants rarely served as sentinels. It wasn't until they'd been in their new groups for five months, on average, that they spent as much time working as lookout as the other mongooses did. The study was published in the journal Current Biology.

Kern和她的团队在南非观察到七种不同的野生小猫鼬。 他们发现新猫鼬很少担任哨兵。平均来说，他们在新团队中待了五个月，他们花费了和其他猫鼬一样多的时间在工作。该项研究结果发表在《当代生物学》杂志上。

Kern thinks that mongooses go through a transition phase before they're fully⁶ integrated into the new group. In part, that's because newcomers arrive exhausted⁷ and underweight. They need time to recover before becoming fully contributing members of mongoose society.

Kern认为，猫鼬在完全融入新的小组之前会经历一个过渡阶段。部分原因是因为新来者很疲惫。他们需要时间恢复，才能成为猫鼬会成员。

But the existing group also takes a while before they trust newcomers. In a playback study, the researchers found that mongooses responded far less to the sentinel calls

[Surveillance call sound]

但是，现有团队还需要一段时间才能相信新人。在回放研究中，研究人员发现猫鼬对前哨呼叫的反应要少得多。

[监视呼叫声音]

of recent immigrants than to those from others they already knew and trusted. But after a few months spent getting to know their new friends, they began to trust them, and reacted appropriately when hearing the alarm call.

[alarm call sound]

但在结识新朋友几个月后，它们们开始相信，并在听到警报时作出适当反应。

[报警呼叫声音]

"When individuals first join, they don't contribute much to sentinel behavior, and when they do, that information is generally ignored. But within five, six months down the line, then those individuals contribute just as much as everyone else does, and residents value their information just as much as everybody else does."

“当个人第一次加入小组后，它们对前哨行为的贡献不大，当他们这样做的时候，这些信息通常被忽视掉，但是在五六个月后，那些猫鼬的贡献与其他猫鼬一样多，猫鼬们会重视他们的信息，就像信任其他猫鼬一样。“

Ultimately, increased group size really is beneficial to all members of a group—new immigrants just need a chance to get settled.

最终，团队规模的增加真的对一个团体的所有成员都有好处 - 新加入的猫鼬只需要一个适应的机会。