Inside the killer whale matriarchy - Darren Croft

翻译人员: Beichen Ding 校对人员: David Shi

Off the rugged coast of the pacific northwest,

在崎岖的太平洋西北部海岸线，

pods of killer whales inhabit the frigid waters.

一群虎鲸生活在冰冷的海水里。

Each family is able to survive here

每个虎鲸家庭之所以能够在这里生存，

thanks mainly to one member,

是因为它们的一个家庭成员，

its most knowledgeable hunter:

是经验丰富的猎手：

the grandmother.

它们的祖母。

These matriarchs can live eighty years or more,

这些女族长们可以活八十年或者更多，

while most males die off in their thirties.

而家庭中的男性成员 通常在它们 30 多岁时死去。

Though killer whales inhabit every major ocean,

尽管虎鲸分布在世界各处，

until recently we knew very little about them.

直到最近我们对它们都知之甚少。

The details of their lives eluded scientists

学界中一直缺乏对它们生活习性的研究，

until an organization called the Center for Whale Research

直到 1976 年，一个叫做鲸类研究中心的组织

began studying a single population

开始对一群生活在

near Washington State and British Columbia in 1976.

华盛顿州和英属哥伦比亚的虎鲸进行研究。

Thanks to their ongoing work,

得益于科学家们的工作，

we’ve learned a great deal about these whales,

我们能够了解这群

known as the Southern Residents.

被称为“南方居民”的鲸鱼。

And the more we learn,

而我们越深入研究，

the more this population’s elders’ vital role comes into focus.

虎鲸族群中的女族长的角色越显得重要。

Each grandmother starts her life as a calf

每一个“祖母”都从幼崽长大，

born into her mother’s family group, or matriline.

出生在它们母亲的家族， 或是说，一个母系氏族中。

The family does everything together,

家庭成员聚在一起生活、

hunting and playing, even communicating through their own unique set of calls.

打猎和玩耍，甚至通过 它们独特的鸣叫进行交流。

Both sons and daughters spend their entire lives with their mothers’ families.

鲸鱼公崽和母崽的一生 都会生活在它们的母系家族。

That doesn’t mean a young whale only interacts with her relatives.

但这不意味着年轻的鲸鱼 只和它的亲属们互动。

Besides their own special calls,

除了一些特殊的鸣叫，

her matriline shares a dialect with nearby families,

一个母系氏族通常与邻近的家庭们共享方言，

and they socialize regularly.

它们中的成员因此可以频繁社交。

Once a female reaches age fifteen or so,

当雌性鲸鱼到了 15 岁左右，

these meetings become opportunities to mate with males from other groups.

这样的邻里聚会就成为了它们的求偶机会。

The relationships don’t go much beyond mating—

这种跨家庭的关系通常仅仅是为了交配，

she and her calves stay with her family,

交配过后，雌性和雄性鲸鱼，

while the male returns to his own mother.

会分别回到它们的母亲身边。

Until approximately age forty,

从 15 岁到 40 岁，

she gives birth every 6 years on average.

雌性鲸鱼平均每隔六年产子。

Then, she goes through menopause—

之后，它就会绝经，

which is almost unheard of in the animal kingdom.

这在动物王国中基本上绝无仅有。

In fact, humans, killer whales and a few other whales

事实上，只有人类、虎鲸

are the only species whose females continue to live for years

和一些其它鲸类的雌性， 在绝经之后

after they stop reproducing.

仍然会存活一段时间。

After menopause,

在绝经后，

grandmothers take the lead hunting for salmon,

祖母们领头带着家庭捕猎鲑鱼，

the Southern Residents’ main food source.

“南方居民”的主要食物来源。

Most of the winter they forage offshore,

大多数冬天它们在海上觅食，

supplementing salmon with other fish.

既捕捉鲑鱼也捕捉其他鱼类。

But when the salmon head towards shore in droves to spawn,

但当鲑鱼成群结队地 游往岸边产卵时，

the killer whales follow.

虎鲸会跟着它们。

The matriarch shows the younger whales

女族长会向年轻的鲸鱼展示

where to find the most fertile fishing grounds.

哪里是最肥沃的渔场。

She also shares up to 90% of the salmon she catches.

女族长还将它高达 90% 的猎物 分享给其它成员。

With each passing year,

每过一年，

her contributions become more vital:

她的贡献都变得更加重要：

overfishing and habitat destruction have decimated salmon populations,

过度捕捞和栖息地破坏 导致鲑鱼数量减少，

putting the whales at near-constant risk of starvation.

使得鲸鱼面临着持续饥饿的危险。

These grandmothers’ expertise

这些祖母的经验技巧

can mean the difference between life and death for their families–

是它们家族生存的关键。

but why do they stop having calves?

但是它们为何会停止产子呢？

It’s almost always advantageous for a female to continue reproducing,

对雌性来说，维持生育能力通常是一个优势，

even if she also cares for her existing children and grandchildren.

即使她们需要照顾自己的孩子和孙子们。

A couple unique circumstances change this equation for killer whales.

几个独特的环境导致 这个定律在虎鲸群体中不存在。

The fact that neither sons or daughters

首先，无论是儿子还是女儿，

leave their families of origin is extremely rare—

离开它们原生家庭的现象都极为罕见。

in almost all animal species,

在几乎所有的动物物种中，

one or both sexes disperse.

两性之一或之二会离开原生家庭。

This means that as a female killer whale ages,

这意味着当雌性虎鲸长大时，

a greater percentage of her family

它直系亲属（包括它的孩子和孙子）的占比，

consists of her children and grandchildren,

会越来越大，

while more distant relatives die off.

而其它的旁系亲属的占比，会不断减少。

Because older females are more closely related to the group than younger females,

由于年老的雌性虎鲸和家庭的纽带更为紧密，

they do best to invest in the family as a whole,

它们也愿意为家庭付出更多，

whereas younger females should invest in reproducing.

而年轻雌性会将更多精力用于繁殖上。

In the killer whale’s environment,

在虎鲸的生存环境中，

every new calf is another mouth to feed

多一个幼崽就多一张口，

on limited, shared resources.

而食物资源却总是有限。

An older female can further her genes without burdening her family

年长的母鲸可以通过支持它的成年儿子

by supporting her adult sons,

来进一步维持她的基因， 而不给自己的家庭带来负担，

who sire calves other families will raise.

因为它成年儿子的后代 将由其它鲸群抚养。

This might be why the females have evolved

这也许就是雌性鲸鱼在中年后

to stop reproducing entirely in middle age.

绝经的原因。

Even with the grandmothers’ contributions,

即使祖母们付出了十分努力，

the Southern Resident killer whales are critically endangered,

“南部居民”虎鲸的生存仍然岌岌可危。

largely due to a decline in salmon.

鲑鱼的减少是主要原因。

We urgently need to invest in restoring salmon populations

我们迫切需要加强恢复鲑鱼种群的投资，

to save them from extinction.

来保护鲸鱼使其免于灭绝。

In the long term, we’ll need more studies like the Center for Whale Research’s.

从长远来看，我们需要更多 像鲸类研究中心的研究。

What we’ve learned about the Southern Residents

我们了解的“南方居民”的生活习性，

may not hold true for other groups.

可能不适用于其它虎鲸群体。

By studying other populations closely,

只有通过详细研究其它鲸鱼族群，

we might uncover more startling adaptations,

我们才可能在它们的生存面临危险之前，

and anticipate their vulnerabilities to human interference

了解更多虎鲸为了 应对人类干扰的变异

before their survival is at risk.

和预测它们在哪些方面 对人类行为会比较脆弱。