Inside the killer whale matriarchy - Darren Croft

譯者: Lilian Chiu 審譯者: Helen Chang

Off the rugged coast of the pacific northwest,

在太平洋西北部 高低不平的海岸外，

pods of killer whales inhabit the frigid waters.

寒冷的水域中住著成群的虎鯨。

Each family is able to survive here

每個虎鯨家庭能在這裡存活，

thanks mainly to one member,

主要都要感謝其中一位成員，

its most knowledgeable hunter:

家中最有知識的狩獵者：

the grandmother.

祖母鯨。

These matriarchs can live eighty years or more,

這些女族長可以活到八十歲以上。

while most males die off in their thirties.

大部分的公鯨頂多活到三十多歲。

Though killer whales inhabit every major ocean,

雖然每片大海洋中都有虎鯨居住，

until recently we knew very little about them.

在最近之前，我們 對牠們的了解非常少。

The details of their lives eluded scientists

科學家也不知道牠們的生活細節，

until an organization called the Center for Whale Research

直到一個叫做 「鯨魚研究中心」的組織

began studying a single population

於 1976 年開始在華盛頓州

near Washington State and British Columbia in 1976.

及不列顛哥倫比亞省 附近研究單一族群。

Thanks to their ongoing work,

因為有這項進行中的研究， 我們才能更了解

we’ve learned a great deal about these whales,

這些所謂的「南方定居虎鯨」。

known as the Southern Residents.

And the more we learn,

隨著我們知道越多，就越發現到

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

這個族群中長老 所扮演的角色有多重要。

Each grandmother starts her life as a calf

每一隻祖母鯨剛生出來時 也只是小鯨魚仔，

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

生在母鯨或母系的家族當中。

The family does everything together,

全家會一起做所有的事，

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

不論是獵食、玩樂，甚至透過 牠們自己獨特的一組叫聲來溝通。

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

不論性別，孩子一生 都和母親的家庭一起生活。

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

這不表示年輕鯨魚 只會和牠的親戚互動。

Besides their own special calls,

除了牠們自己的特殊叫聲之外，

her matriline shares a dialect with nearby families,

牠的母系也會和鄰近的 其他家庭有共通的方言，

and they socialize regularly.

且牠們常常會社交。

Once a female reaches age fifteen or so,

母鯨到了十五歲左右時，

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

這些會面就變成了 和其他族群的公鯨交配的機會。

The relationships don’t go much beyond mating—

牠們的關係不太會超越交配——

she and her calves stay with her family,

母鯨和牠生的小鯨魚 留在母鯨的家庭生活，

while the male returns to his own mother.

公鯨則會回到牠自己的母親身邊。

Until approximately age forty,

母鯨平均每六年會生一次孩子，

she gives birth every 6 years on average.

直到約四十歲為止。

Then, she goes through menopause—

接著，牠就會進入更年期——

which is almost unheard of in the animal kingdom.

在動物王國中幾乎 沒聽過這種現象。

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

事實上，人類、虎鯨， 和少數幾種其他鯨魚

are the only species whose females continue to live for years

是僅有的物種，

其雌性在停止生育之後 還繼續存活許多年。

after they stop reproducing.

After menopause,

在更年期之後，

grandmothers take the lead hunting for salmon,

祖母就會負責帶頭狩獵鮭魚，

the Southern Residents’ main food source.

那是南方定居虎鯨的 主要食物來源。

Most of the winter they forage offshore,

冬天大部分時間， 牠們會在近海搜索，

supplementing salmon with other fish.

除了鮭魚之外還用 其他魚類來補充。

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

但當鮭魚為了產卵 而成群朝向海岸游去時，

the killer whales follow.

虎鯨會跟隨著。

The matriarch shows the younger whales

女族長會教導較年輕的鯨魚，

where to find the most fertile fishing grounds.

要到哪裡找最豐產的獵魚場。

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

牠也會把 90% 牠抓到的 鮭魚分享出來。

With each passing year,

隨著每一年過去，

her contributions become more vital:

她的貢獻變得更重要了：

overfishing and habitat destruction have decimated salmon populations,

過度捕撈和破壞棲息地，

造成鮭魚大量死亡，

putting the whales at near-constant risk of starvation.

讓鯨魚經常會有挨餓的風險。

These grandmothers’ expertise

這些祖母鯨的專業知識

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

左右牠們家人的生死——

but why do they stop having calves?

但牠們為什麼會停止生小鯨魚？

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

雌性動物持續繁殖， 幾乎都是比較有利的，

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

即使牠也得同時照顧 既有的孩子和孫子。

A couple unique circumstances change this equation for killer whales.

對於虎鯨來說，有幾個 獨特的狀況改變了這個等式。

The fact that neither sons or daughters

下一代雄鯨和雌鯨都不離開 原生家庭的這個事實

leave their families of origin is extremely rare—

極為罕見。

in almost all animal species,

幾乎所有的動物物種

one or both sexes disperse.

至少有一種性別會離家。

This means that as a female killer whale ages,

這就表示，隨著雌性虎鯨年齡漸長，

a greater percentage of her family

她的家庭中就有更高比例的成員 是她的孩子和孫子，

consists of her children and grandchildren,

while more distant relatives die off.

遠親則逐漸凋零。

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

由於年長的母鯨比年輕的 和群體更親，

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

年長者為整個家庭付出最適宜，

whereas younger females should invest in reproducing.

而年輕的母鯨則投入繁殖。

In the killer whale’s environment,

在虎鯨的環境中，

every new calf is another mouth to feed

每隻新生的鯨魚 是一張嗷嗷待哺的嘴巴，

on limited, shared resources.

要拿有限、共享的資源去養牠。

An older female can further her genes without burdening her family

較年長的雌性可以擴展牠的基因， 卻不會給牠的家庭帶來負擔，

by supporting her adult sons,

做法就是支持牠的成年兒子，

who sire calves other families will raise.

成年兒子所生的小鯨魚 會由其他家庭來撫養。

This might be why the females have evolved

這可能就是為什麼雌性會演化成

to stop reproducing entirely in middle age.

在中年就完全停止繁殖。

Even with the grandmothers’ contributions,

即使有祖母鯨的貢獻，

the Southern Resident killer whales are critically endangered,

南方定居虎鯨仍然嚴重瀕臨絕種，

largely due to a decline in salmon.

主要的原因是鮭魚的數量大減。

We urgently need to invest in restoring salmon populations

我們急需要投入資源 來恢復鮭魚的數量，

to save them from extinction.

以拯救虎鯨不要絕種。

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

長期來看，我們會需要更多研究， 就像鯨魚研究中心所做的研究。

What we’ve learned about the Southern Residents

我們所了解到關於 南方定居虎鯨的知識

may not hold true for other groups.

不見得適用於其他族群。

By studying other populations closely,

藉由仔細研究其他族群，

we might uncover more startling adaptations,

我們可能會發現更多 驚人的適應變化，

and anticipate their vulnerabilities to human interference

並在牠們的生存受到威脅之前，

就預測出人類的干預 對牠們的影響有多大。

before their survival is at risk.