鲸鱼频繁搁浅的一百种原因：有一种你可能根本想不到｜科学60秒

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2023-05-11 15:05

我们需要再次拯救鲸鱼吗

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1975年6月，绿色和平（GreenPeace）组织的几位成员在一次反捕鲸行动中表示，一个180米的浮动屠宰场能够在不到半小时内处理一整头鲸鱼，还打出了著名的口号：“拯救鲸鱼（Save the Whales）。”

绿色和平组织不断曝光和阻止商业捕鲸的行为最终发挥了作用。国际捕鲸委员会（International Whaling Commission）在1985年颁布了暂停捕鲸的规定。数量一度减少超过95%的座头鲸，开始恢复繁荣。

但是，最近发生了一些令人担忧的事情：鲸鱼尸体又开始被冲上海岸了。有很多鲸鱼是在2022年冬天搁浅的，但在这几周，更多的鲸鱼在美国东海岸搁浅，海洋保护组织正试图弄清为什么会发生这种情况。

这一切引出了一个问题——我们是否需要再次拯救鲸鱼？

比较解剖学家乔伊·赖登伯格（Joy Reidenberg）说：“最近所发生的是所谓的异常死亡事件。这是一个官方名称，指的是某一特定鲸鱼物种被冲上岸的尸体数量不同寻常。”赖登伯格同时也是一位从事鲸鱼尸体解剖的科学家，“所以，当一只动物尸体被冲上岸，我们做的第一件事就是检查尸体的外部。这只动物为什么会死？我们能从它的身体上了解到什么？”

科学家们目前还不能确认导致这种不寻常死亡事件的原因，赖登伯格说：“许多鲸鱼尸体似乎都存在某种迹象，表明它们的死因是与人类的互动，这种互动实际上主要是船只的撞击。”

为了验证这一可能性，赖登伯格团队必须深入探查鲸鱼的身体。“我们寻找的是，是否有任何证据表明受伤的地方有出血现象。”

这并不容易。一头成年座头鲸体重高达三四十吨，体长近似两辆大巴首尾并列那么长。赖登伯格：“因此，当鲸鱼处于船舶的轨道上时，行船能让鲸鱼完全弯成两半，折断它的脊柱，撞碎它的肋骨，压毁它体内的重要器官，鲸鱼的身体也可能会产生切口，足够深的切口可能是致命的。”

但船只撞击并不总能说明问题的全部。

赖登伯格：“如果在检查组织时没有看到出血或淤伤的迹象（淤伤是由血管破裂造成的，血液渗入周围组织形成深色斑块），那么鲸鱼就是在死后被撞的，因为已死的鲸鱼不会流血。所以也可能是鲸鱼已经死了，之后又被船撞了一下，在这种情况下，这些划痕可能不是在它们活着的时候造成的。”

毕竟除了船只撞击之外，其他人类与鲸鱼的互动也会导致它们的死亡。赖登伯格：“比如它们可能被渔具缠住，不能正常游动，不能正常进食，特别是如果鱼线缠在嘴上，它们可能会被活活饿死。”

鲸鱼也会因为病毒和细菌感染而生病。赖登伯格：“所以，弄清死亡的原因可能是非常困难的。”

但是作为一个科学家，赖登伯格有件事想澄清。海上风力发电站最近受到了很多关注，许多人相信正是这些发电站导致了最近一连串的鲸鱼死亡事件。赖登伯格：“这是因为在水中产生声音的东西会干扰鲸鱼的听觉，甚至会影响它们与其他鲸鱼的交流。”

然而，有些东西并不符合事实。赖登伯格：“现在并没有证据支持风电场行业对这些鲸鱼有任何影响，无论是风电场本身，还是为确定风电场位置而进行的地震勘测。这些声音不在鲸鱼能够听到的频率范围内。因此，这不太可能导致它们‘失聪’。”

赖登伯格对可能导致鲸鱼死亡数量突增的原因有另一种解释，一种你可能从没想过的解释……[查看全文]

Do We Need To Save the Whales Again?

[Clip of Greenpeace Activist] This is a 600-foot floating slaughterhouse capable of processing an entire whale in less than half an hour.

Tulika Bose: In June of 1975, several GreenPeace activists set sail under a banner which would become a famous slogan.

[Clip of Greenpeace Activist] We were left with no alternative but to carry out our pledge to use our bodies as shields.

Bose: Save the Whales.

[Clip of Greenpeace Activist] We stopped one chaser boat already and saved one plot of whales. Not bad for a morning’s work.

Bose: Greenpeace’s constant campaigning against commercial whaling worked.

Bose: The international whaling commission issued a moratorium on whale hunting in 1985. Humpback whales — a population once decimated by more than 95% — started making a comeback.

[Whale Sounds]

Bose: But — something’s recently happened.

[NEWS CLIP] Concern at the Jersey Shore after yet another whale washed up on an Atlantic City beach.

Bose: Dead whales have started washing up on shores again — many over the last winter.

[NEWS CLIP] More whales are washing up on the East Coast this weekend and now marine conservation groups are trying to figure out why it’s happening.

Bose: It all begs the question — do we need to save the whales again?

Joy Reidenberg: What's happening right now is what's called an unusual mortality event. That is the official name for an unusual number of dead animals washing up of a particular species.

Bose: That’s Joy Reidenberg. She’s a comparative anatomist and a scientist that also does whale necropsies — or in layman’s terms, whale autopsies.

Reidenberg: So when an animal washes ashore dead, the first thing we do is we examine the outside of the body. Why did the animal die, and what can we learn from its body?

Bose: Though scientists can’t confirm what’s causing this unusual mortality event — there’s something that Joy can tell us about the dead whales.

Reidenberg: Many of them seem to have some kind of indication that they’ve been killed through an interaction with humans. And that interaction is actually mostly ship strikes.

Bose: And to really verify what’s killed the whale, Joy and a team have to dig inside the body of the whale itself.

Reidenberg: What we look for is, is there any evidence that there was bleeding at the site of the injury.

Bose: This by the way — isn’t easy. A fully grown humpback whale, for example, can weigh up to 80,000 pounds and be as long as a schoolbus.

Reidenberg: So when the whale is in the path of a ship, it can actually bend the whale completely in half and break its spine, it can crush its ribcage and crush the vital organs inside, and then it can have slices through its body and those slices can be fatal if they slice through deep enough.

Bose: But ship strikes don’t always tell the whole story.

Reidenberg: If we look at the tissues and we don’t see evidence of bleeding, or bruising which is of course caused by blood vessels rupturing and causing this bloody stain inside the tissue, then the animal was hit after it was already dead — because a dead animal doesn’t bleed. It could be that the animal was already dead and it just got run over by a ship. In which case those slice marks might have not happened to a live animal.

Bose: And that’s because there are also other human interactions with whales that kill them besides ship strikes alone.

Reidenberg: Such as they could get tangled up in fishing gear. They often can't swim very well, they can't feed very well, especially if the lines wrap around the mouth, and the animal could actually die of starvation.

Bose: Not to mention — whales also get sick from viruses and bacterial infections.

Reidenberg: So — sometimes figuring out what the cause of death is can be extremely hard.

Bose: But — there’s something that Joy wants to clarify, as a scientist. Wind farms have been getting a lot of attention lately for allegedly playing a role in the recent spate of whale deaths.

[NEWS CLIP] Too many dead whales are washing ashore, and that has activists calling on President Biden to offshore — to do something about offshore wind energy activity.

Reidenberg: That’s because things that generate sound in the water can interfere with a whale’s ability to hear and can even affect their ability to communicate with other whales.

Bose: However — Joy says that something doesn’t add up.

Reidenberg: Right now there is no data to support that the wind farm industries, whether it's the wind farms themselves, or the seismic surveys that are done to determine where to place a wind farm have any effect on these whales.

Bose: Here’s why.

Reidenberg: Those sounds are not in the frequency range that these whales hear. So it's unlikely that that's causing their deafness.

Bose: In fact — Joy has another explanation for what could be causing the sudden increase in whale deaths. It’s not what you might think...[full transcript]

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