In October 2015, I made the acquaintance of a lonesome crocodile living in a small river in Khao Yai National Park, Thailand. When we met, it was doing some very serious resting (Figure 1). So deep did its slumber seem that you might have been forgiven for believing you could walk right up to it without it ever knowing. I decided to keep a safe distance, however, having heard that crocodiles might be unihemispheric sleepers, and therefore might “keep one eye open” when they take a siesta! Moreover, although its eyes seemed to shed no tears, I was not about to trust in the old idea that a crocodile who wants to eat you weeps before striking. And I'm pretty certain I would not have been persuaded to decide differently had I known at the time that some actually might…

The idea that crocodiles cry in order to catch sympathetic humans goes back a long way. For example, in 1590, in his epic poem The Faerie Queene, Edmund Spenser tells us that the crocodile weeps woeful, tender tears in order to lure and gobble up anyone so foolish as to be taken in and offer consolation. And during a (damningly slave‐trading) voyage to the Caribbean in 1565, commanded by Sir John Hawkins, gentleman adventurer John Sparke recorded that whenever the local crocodiles were hungry they would cry and sob “like a Christian body” to provoke the approach of unwary comforters, and then snatch them up – see Richard Hakluyt's 1589 collative work republished in The Principal Navigations, Voyages, Traffiques and Discoveries of the English Nation, Volume XV (1890; Edinburgh: E & G Goldsmid). In earlier times, however, it was thought that crocodiles only cried after they grabbed you. In his 13th‐century work De proprietatibus rerum, Franciscan monk Bartholomaeus Anglicus noted an ancient belief that if a crocodile came upon someone at the water's edge it would certainly try to catch him, but would weep over his dead body before tucking in. And around 400 CE, St Asterius wrote that a crocodile weeps when all that is left is his victim's bony head, but only because his meal is finished – see Ad Vingerhoets’ Why Only Humans Weep: Unravelling the Mysteries of Tears (2013; Oxford, UK: Oxford University Press).

But while “crocodile tears” forever became a metaphor for hypocrisy, by the early 1700s the idea that crocodiles actually cried was already fading, and in 1924 it was roundly declared a myth during a reading of George Lindsay Johnson's ophthalmological research at the Royal Society in London (doi.org/10.1098/rstb.1927.0007). And yet, by the time I met my crocodile, scientists had, unbeknownst to me, reported the filming of captive crocodilians indeed producing lunchtime tears (BioScience 2007; 57: 615–17)! Of the two common caimans (Caiman crocodilus), two Yacare caimans (Caiman yacare), and three American alligators (Alligator mississippiensis) examined, all but one Yacare and one common caiman produced moisture and even bubbles in their eyes just before, during, or after they ate. Upon learning this in 2020, I turned quickly to the internet and watched loads of close‐up videos of crocodilians in rivers, lakes, and ponds, or on their banks, doing dinner. There was even excellent footage of my very own Khao Yai crocodile munching on a deer (https://bit.ly/35PGOOS). But for the life of me I could see no tears. When I consulted crocodile expert Adam Britton (Charles Darwin University; Darwin, Australia) he confirmed that these secretions are indeed produced, but he pointed out that the animals in the BioScience paper were all fed on dry land, and that “if the crocodile has a wet head, typically if it's in the water or at the water's edge, you wouldn't see [tears] at all”. There was my problem. But since we normally see crocs around water, this raises an interesting question: without film or magnifying technology, how on Earth did observers who lived hundreds of years ago notice this phenomenon?

My reading rekindled my interest in that lone Thai crocodile, and in its enigmatic history. No one knows where it came from; no crocodiles had previously been recorded in the park. Did it get there itself or did someone drop it off in the river? No one knew its sex either – determinations usually require an internal examination. Even its species was a mystery since no one ever found any scats for DNA analysis. After making some inquiries, however, I received a kind letter from Ronglarp Sukmasuang of Kasetsart University (Bangkok, Thailand) whose conservation work includes crocodile reintroductions, and he assured me that his colleague Panya Yongprapakorn had confirmed it to be a male Siamese crocodile (Crocodylus siamensis), a very rare creature indeed. Only some 500 may be left across Southeast Asia. Sadly, he also told me that he had not seen the animal for a very long time, adding heart‐rending weight to rumors I had read about its death.

I felt a little tear welling up.

Adrian Burton

2015年10月，我认识了一只生活在泰国考艾国家公园一条小河里的孤独的鳄鱼。当我们见面时，它正在做一些非常认真的休息（图1）。它的沉睡是如此之深，以至于您可能认为自己可以在不知不觉中走上正轨而被宽恕。但是，我决定与鳄鱼保持安全距离，因为听说鳄鱼可能是半球形的睡眠者，因此在他们午睡时可能“睁大一只眼睛”！而且，尽管它的眼睛似乎没有流泪，但我并不想相信一个古老的想法，那就是一条想要吃掉你的鳄鱼会在罢工前哭泣。而且我敢肯定，如果我当时知道有些人可能会……我不会被说服做出其他决定。

为了抓住有同情心的人类而哭泣的鳄鱼的想法可以追溯到很久以前。例如，在1590年，埃德蒙·斯宾塞（Edm Spenser）在他的史诗《仙境女王》中告诉我们，鳄鱼会哭泣着悲伤而温柔的眼泪，以引诱和吞噬任何愚蠢到可以接受并提供安慰的人。1565年，在约翰·霍金斯爵士（John Hawkins）的指挥下，一次（非常奴隶交易）加勒比海航行中，绅士冒险家约翰·斯帕克（John Sparke）记录说，每当当地的鳄鱼饿了时，他们都会哭泣和抽泣，“像一个基督教徒的身体”来激怒松散的棉被，然后将它们收拾起来–请参阅Richard Hakluyt 1589年的合集作品，该作品在《英国民族的主要航行，航程，交通和发现》中重新出版，第十五卷（1890年；爱丁堡：E＆G Goldsmid）。但是，在更早的时期，人们认为鳄鱼只有在抓住您之后才会哭泣。方济各会的僧侣Bartholomaeus Anglicus在其13世纪的作品De Proprietatibus rerum中指出，一种古老的信念是，如果一条鳄鱼在水边碰到某人，那肯定会设法抓住他，但会在他的尸体上流泪，然后才被塞进去。公元400年，圣阿斯泰里乌斯（St Asterius）写道，鳄鱼只剩下受害者的骨头，就哭了，但这仅仅是因为他的饭已吃完–参见Ad Vingerhoets的《为何只有人类哭泣：揭开眼泪的奥秘》（2013年；英国牛津：牛津大学出版社）。

但是，尽管“鳄鱼的眼泪”永远成为伪善的隐喻，但到1700年代初，鳄鱼实际上哭泣的想法已经淡出，并在1924年乔治·林赛·约翰逊（George Lindsay Johnson）在皇家学会（Royal Society）的眼科研究中全面宣告神话伦敦（doi.org/10.1098/rstb.1927.0007）。然而，到我遇见鳄鱼时，科学家对我不为人知，他们报道了拍摄圈养鳄鱼的过程确实产生了午餐时间的眼泪（BioScience 2007；57：615-17）！在两个常见的凯门鳄（Caiman crocodilus）中，有两个Yacare凯门鳄（Caiman yacare ）和三个美国短吻鳄（Alligator mississippiensis））检查后，除了一只Yacare和一只普通凯门鳄，在进食前，进食中或进食后，它们的眼睛均产生了水分甚至气泡。在2020年得知这一点后，我迅速转向互联网，并观看了许多在河，湖和池塘中或在他们的河岸上吃晚饭的鳄鱼的特写视频。甚至还有我自己的考艾（Khao Yai）鳄鱼在鹿上咀嚼的绝妙镜头（https://bit.ly/35PGOOS）。但是对于我的一生，我看不到眼泪。当我咨询鳄鱼专家亚当·布里顿（查尔斯·达尔文大学；澳大利亚达尔文）时，他确认确实分泌了这些分泌物，但他指出生物科学中的动物纸都是在干燥的土地上喂食的，“如果鳄鱼的头很湿，通常是在水中或在水的边缘，就根本看不到眼泪”。这是我的问题。但是，由于我们通常会在水中看到鳄鱼，所以提出了一个有趣的问题：没有胶片或放大技术，数百年前的观察者在地球上如何注意到这一现象？

我的阅读重新激发了我对那条孤独的泰国鳄鱼及其神秘历史的兴趣。没有人知道它的来源。以前公园里没有鳄鱼记录。它是到达那里还是有人把它扔进河里？也没有人知道其性别-确定通常需要内部检查。由于没有人发现任何可用于DNA分析的粪便，因此即使是其物种也是一个谜。做一些调查之后，但是，我收到了来自农业大学的Ronglarp Sukmasuang（曼谷，泰国），其保护工作包括鳄鱼再引入一种一封信，他向我保证，他的同事班雅Yongprapakorn已证实这是一个男性暹罗鳄（鳄暹罗），确实是一种非常稀有的生物。整个东南亚可能只剩下大约500个。可悲的是，他还告诉我，他已经很长时间没有见过这种动物了，这使我听到有关它死亡的谣言更加沉重。

我感到有点泪流满面。

阿德里安·伯顿（Adrian Burton）