這種企鵝在熱帶安家，七月底在樓頂又見到了ta

德國小鎮斯特拉爾松德（Stralsund）有個海洋館。這個海洋館最著名的地方，在于它的樓頂：二十多米高的大露臺上，吹著習習海風，坐看藍天上云卷云舒，愜意極了。

露臺上有一個不大的水池，里邊堆著假山，假山的洞窩偶爾露出一只毛茸茸的白褐各半的腦袋。再仔細看看那腦袋，不禁讓人大吃一驚，這竟然是一只企鵝？

The OZEANEUM in the northern German port city of Stralsund has a rather satisfying rooftop. Here you can enjoy the refreshing Baltic breeze, see the bright blue summer sky above and enjoy the historic Hanseatic town of Stralsund below.

And in the middle of the rooftop sits a rocky pool. Every now and then, a fluffy brown-and-white head pokes out from one of the artificial nesting caves.

A penguin.

這是夏天七月底，這塊樓頂更是直接承受陽光照射。他們竟然能養自帶燕尾服的企鵝？

什么企鵝這么耐熱？

I had to look twice to trust my own eyes. It was late July and the rooftop was baking under direct sunshine that standing there in a T-shirt already made me feel warm enough. Yet these birds, commonly supposed to appear in below-ice temperature only, appeared perfectly comfortable.

Had someone forgotten to tell the penguins that they belong in Antarctica?

酷暑求生，企鵝脫掉燕尾服

答：洪堡企鵝。

這種企鵝原產地在南美洲西海岸，南緯5度到43度之間，秘魯、智利都有分布。熟悉地理的同學們都知道，這個維度跨越了溫帶、亞熱帶甚至熱帶，但在1799年到1804年的美洲之旅中，德國科學家亞歷山大·馮·洪堡（Alexander von Humboldt）居然發現這里有企鵝在活動，消息一經公布震驚了當時的整個學界。三十年后，德國博物學家弗蘭茨·尤利烏斯·費迪南德·邁恩（Franz Julius Ferdinand Meyen）為這種物種正式命拉丁學名為（Spheniscus humboldti），日常就叫“洪堡企鵝”。

為適應不同的生存環境，洪堡企鵝和南極企鵝在身體條件上有很大不同。大家印象中的南極企鵝一般都是肚子白背部則為黑色或者深藍色，很有利于吸收陽光的熱量進行保暖。

但對生活在低緯度地區的洪堡企鵝，深色羽毛則不利于散熱。相比南極企鵝，洪堡企鵝背部羽毛顏色更淺，也更加稀疏。如果說南極企鵝穿的是保溫效果奇佳的藍黑色毛料燕尾服，洪堡企鵝穿的就是淺色針織衫，散熱效果要好很多。

I had always associated penguins with snow, sea ice and the Antarctic and I personally believe many people did it. But nature, as it often does, had another story to tell.

The Humboldt penguin is native to the coastal region ranging roughly from Peru to central Chile, or between about 5 and 43 degrees south latitude. As the digit shows, some of their colonies even live surprisingly close to the equator.

The species owes its name to the German explorer and naturalist Alexander von Humboldt, who observed these penguins during his famous expedition across Latin America between 1799 and 1804. His reports astonished European scientists of the time. Decades later, German zoologist Franz Julius Ferdinand Meyen formally described the species and named it Spheniscus humboldti in Humboldt's honor.

為了適應較高氣溫，洪堡企鵝的羽毛進一步演化得更短、更薄。它們的羽毛長的短小精干，一點都沒有南極親戚的厚重感。就這點又小又短的羽毛，洪堡企鵝還要每年換一換，而且是從頭到腳的換，號稱“毀滅性換羽”。它的臉、嘴等部位干脆不長毛，大片的粉紅色皮膚裸露在外邊，又萌又涼快。

一位朋友UrLunkwill貢獻的圖片，能清楚看到洪堡企鵝粉嘟嘟的小臉蛋。

脂肪具有保溫作用，因此體型較胖的動物通常更耐寒。所以南極企鵝一般都是肉乎乎圓滾滾的，身上幾乎找不到凹陷下去的地方，一層肥油把自己包的嚴嚴實實。洪堡企鵝反其道而行之，比南極的親戚們瘦了不止一圈，耐熱程度也就提高了不止一個檔次。

They have even kept diet. Antarctic penguins resemble little walking barrels as thick layers of fat help conserve heat in water that can remain below freezing. In deep contrast, Humboldt penguins are noticeably slimmer, carrying less insulation and dissipating heat more efficiently.

人們可能會認為，洪堡企鵝的祖先可能從南極逐漸向北遷徙，并在長期演化中逐步適應了低緯度地區的高溫環境。

不過，這一推測并不符合目前學界的主流觀點。2017年的《自然·通訊》（Nature Communications）登出一篇論文，研究了在新西蘭發現的約6000萬年前的古代企鵝化石。現在學界的主流認知是，企鵝是在相對溫暖的時代誕生于今天新西蘭附近，后來隨著洋流游到南極，在那里進化出了厚厚的羽毛和圓滾滾的體型，通過這些措施適應了極地的寒冷。

在企鵝誕生的那個時代，地球的平均溫度比現在高好幾度，南極甚至都還沒有形成冰蓋。這意味著，企鵝的演化路徑與上述推測恰好相反：它們起源于相對溫暖的地區，隨后遷徙至南極，又遇上了全球溫度降低，在以萬年為計數的單位里長出了濃密的黑藍色羽毛，吃的圓滾滾，變成了現在的模樣。

為了生存而適應環境的桂冠，當由洪堡企鵝和南極企鵝共享。

自助者，天助之

企鵝的命運要靠自我奮斗，也要看氣候的行程。畢竟南極均溫在零下十幾攝氏度甚至幾十攝氏度，熱帶確實動輒三十多攝氏度，企鵝很難同時適應這兩地的氣溫。

洪堡企鵝的存在，要感謝大自然的饋贈。洪堡在美洲科考的過程中，發現洪堡企鵝生活的地區平均海水溫度通常在15-18攝氏度之間，氣溫低至4攝氏度高也就是30攝氏度，比一般的熱帶地區要低。再往地理學上考察，洪堡發現原來這里沿岸有一條寒流經過，降低了海水溫度也順便降低了氣溫。

Yet even all these adaptations cannot fully explain how a penguin manages to thrive so close to the tropics because the two environments are too strikingly contrast to each other.

The question was also answered by Humboldt. During his South American expedition, Humboldt noticed that coastal waters were unexpectedly cold despite their low latitude. Investigating further, he identified a vast current flowing northward from Antarctic waters along the Pacific coast.

Today it is known as the Humboldt Current, or the Peru Current. As its name shows, it cools both the sea and the air above it, creating a remarkably mild coastal climate near Peru. Sea surface temperatures often remain between 15 and 18 C, far cooler than one would expect at those latitudes.

洪堡寒流示意圖。（圖由AI生成）

洪堡發現的寒流后來被命名為洪堡寒流，也因為經過秘魯等國沿岸海域而被稱作秘魯寒流。對洪堡企鵝來說，這條寒流是個不可取代的庇護所，夏天實在熱到不行了，能一個猛子扎到涼爽的海水中，給自己降降溫。更關鍵的是，寒流帶來了豐富的食物，企鵝是愛吃肉的動物，其食譜包括魚蝦蟹螺，洪堡寒流帶來了大量磷蝦，這本來是南極才有的生物，現在卻給熱帶的企鵝提供了美餐。

For Humboldt penguins, the current functions as a giant natural air conditioner that even people in Europe are dreaming of. Whenever the sun becomes too intense, they simply dive into cool seawater.

Even more importantly, the Humboldt current supports one of the richest marine ecosystems on Earth. Cold water rising from the deep carries abundant nutrients to the surface, triggering explosive growth of plankton, which in turn feeds enormous populations of fish, squid and krill.

這個發現也讓洪堡達成了既命名企鵝又命名洋流的成就，縱觀整個人類歷史，這樣的例子也不多見。再算上洪堡大學、洪堡基金會、洪堡論壇……感覺在德國，什么都能用洪堡命名。

柏林洪堡論壇門口

進一步把格局打開，我們會發現這世界上除了洪堡企鵝，還有這么幾種企鵝生活在溫帶、熱帶、亞熱帶：

麥哲倫企鵝（Magellanic penguin）分布于阿根廷和智利南部，那里有福克蘭寒流幫助降溫；

非洲企鵝（African penguin）生活在南非和納米比亞沿岸，受本格拉寒流（Benguela Current）影響，溫度也可控；

加拉帕戈斯企鵝（Galápagos penguin）干脆生活在赤道附近的加拉帕戈斯島，洪堡寒流和克倫威爾洋流在這里造出了一個不那么熱的小小家園，讓企鵝們能對抗一年好幾個月的陽光直曬。

筆者這次造訪的斯特拉爾松德也不例外。這個小鎮位于德國波羅的海沿岸，是典型的的溫帶海洋性氣候。感謝波羅的海給力的調節作用，這里雖然緯度跟中國的漠河差不多，卻是冬無嚴寒、夏無酷暑，全年降水均勻，普通人在這里生活的十分愜意。洪堡企鵝也沾了這點光，過上了不冷不熱的生活，企鵝館常年布置在樓頂露天，和游客們一起欣賞這藍天白云。

洪堡企鵝居住的屋頂全景

從屋頂往外看

這就是大自然的神奇之處。洶涌的大洋里有和陸地河流類似的洋流，終年不息地朝著一個方向流動，帶動海洋里的本來渺小的生命隨著它遷徙，旅程動輒跨越上萬公里。海水的溫度影響了沿岸，改變了原本酷熱的環境，讓小小的企鵝在亞熱帶甚至熱帶也有自己的立足之地。

Invisible to us, enormous currents circulate endlessly around the globe, transporting heat, nutrients and life across thousands of kilometers. A slight change in water temperature can reshape an entire coastline, allowing a bird that most of us associate with icebergs to flourish in subtropical South America — or on the roof of a museum in northern Germany.

再往大了想，地球或許也是這樣。宇宙環境是普遍極端的，恒星溫度高達數億開爾文，缺少光照的空間溫度則接近絕對零度，都是生命不敢想象的嚴酷。但就在銀河系一個小小的角落里，多種因素共同造就了地球這么一顆小小的巖質行星，恰好離太陽不遠不近有液態水，經過很多億年的演變，終于被播撒上生命成了我們的家園。

從這個角度看，我們人類主動適應環境，常年不斷進化，全球各緯度都能生存，也和洪堡企鵝一樣，都是奇跡般的存在。

Sometimes, standing beside a penguin pool, you end up learning more about the planet than about the penguins themselves. The Earth, a rocky planet with so accurately proper distance to the sun that liquid water can exist on it and breed life for 3.8 billion years, is also in a small and subtle corner of the Universe where the natural forces accidentally make good.

Perhaps that is what Humboldt as a science teacher would have appreciated.

記者：張周項

跟著China Daily

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