出生之前，動物們就在聽取父母的胎教了

人類幼崽：出生前不如抄抄斑胸草雀的作業。

聲音能夠傳遞很多資訊，例如警示動物潛在的危險 ［疣猴的喊叫］，讓父母知道孩子們餓了 ［羊羔的咩咩聲］，也可能作為求偶訊號、領地警告，或者僅僅是讓其他動物知道自己的存在 ［狼群此起彼伏的嚎叫］。

事實證明，連胚胎也會注意到這種自然聲景。越來越多的研究顯示，很多動物的胚胎髮育都會受到環境中聲音的指引——這個技巧能讓它們在出生後更具優勢。

澳大利亞迪肯大學（Deakin University）的邁林·馬裡耶特（Mylene Mariette）偶然發現：“在我研究的物種——斑胸草雀（Taeniopygia guttata）中，我們發現鳥爸爸和鳥媽媽會在天氣炎熱的時候發出一種特殊的叫聲。這種‘熱浪警告’能幫助胚胎的發育為高溫做好準備。當時我正在研究鳥巢中斑胸草雀父母的交流，我注意到，在獨自孵蛋時，雄鳥或雌鳥偶爾會發出一種與平時明顯不同的叫聲。”

［斑胸草雀的熱浪警告］

她想到，由於附近並沒有其他鳥，父母可能是在和鳥蛋說話。於是她留在鳥舍裡，繼續偷聽——“真相很快就浮出水面，斑胸草雀父母們只會在天氣炎熱的時候對鳥蛋發出這樣的叫聲。”但這對發育中的雛鳥有什麼影響呢？

為了找到答案，馬裡耶特“借走”了斑胸草雀的蛋。她把這些蛋置入孵化器中，並給它們播放斑胸草雀父母的“熱浪警告”，或是斑胸草雀父母在換班時發出的叫聲，然後再將它們送回巢中。在雛鳥破殼而出時，馬裡耶特發現那些透過“熱浪警告”預知了高溫的雛鳥體型，要比其他雛鳥都小。

“我們當時還挺驚訝，但後來發現在高溫下不長那麼大是有利的，這些斑胸草雀在成年後會產下更多的後代。這可能是因為它們避免了在高溫下長得過大所增加的成本——大量的能量消耗。”

Animal Kids Listen to Their Parents

Even before Birth

Karen Hopkin： Sounds can convey a lot of information。 They can alert animals to potential danger ［CLIP： Colobus monkeys vocalize］， let parents know when their offspring are hungry ［CLIP： Baby lamb bleats］， or serve as mating calls， territorial warnings or just a way to let others in the area know that you’re there ［CLIP： Wolves in chorus］。

And it turns out that even embryos pay attention to this natural soundscape。 A growing body of research shows that for many animal species， embryos use audio from their environment to guide their development—a trick that can give them an advantage after they’re born。

Mylene Mariette： So in the species that I study， the zebra finch， we found that the parents make a special call when it’s hot。 And those heat calls prepare the development of the embryos for heat。

Hopkin：Mylene Marietteof Deakin University in Australia。 She made this discovery by chance。

Mariette： I was studying the communication between the parents at the nest when I noticed that sometimes， when the parent was incubating the eggs by itself， it was producing a call that was quite different to the others。

［CLIP： Zebra finch heat call］

Hopkin： And since there was no one else around， she wondered whether that parent might be talking to the eggs。 So she hung around the aviary and listened in。

Mariette： So it soon became apparent that the parents were only calling to the eggs when it was really hot。

Hopkin： But what did that do for the developing chicks？

To find out， Mariette started borrowing the eggs。 She’d take them to the incubator and play them either the zebra finch heat call or a different call， one that the parents make when they change shifts。 Then she’d return them to their nests。

When the chicks hatched， Mariette found that the birds that had heard about the heat were actually smaller than the others。

Mariette： It was a little bit surprising at the time， but we then found that reducing growth in the heat was advantageous because those individuals then produced more babies when they were adult。 And that’s probably because they avoided the costs of growing big in the heat， which takes a lot of energy。

Hopkin： And birds are not the only ones who learn about prevailing conditions via embryonic eavesdropping…

[full transcript]

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論文資訊

Mariette， M。M。， Clayton， D。F。 and Buchanan， K。L。， 2021。 Acoustic developmental programming： a mechanistic and evolutionary framework。Trends in Ecology & Evolution。

doi：10。1016/j。tree。2021。04。007

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