They call it stupid hot for a reason: Heat muddles animal brains
They call it stupid hot for a reason: Heat muddles animal brains
人们说“热到降智”是有原因的：高温会扰乱动物的大脑
On a blazing hot day in South Africa, female southern pied babblers can’t think straight. The medium-sized black-and-white birds are trying to get at tasty mealworms behind a see-through barrier. On cooler days, the birds can quickly figure out that all they have to do is go around the small wall of plastic. But when the mercury goes up, the birds just keep stubbornly pecking at the barrier. 在南非一个烈日炎炎的日子里，雌性南部斑鸫鹛（southern pied babblers）无法进行正常的思考。这些中等体型的黑白相间的鸟儿正试图穿过一道透明屏障去获取美味的面包虫。在凉爽的日子里，这些鸟儿能很快意识到，它们只需要绕过那道小塑料墙即可。但当气温升高时，它们却只会固执地对着屏障不断啄击。
That experiment is part of a growing body of research showing that animals get their minds muddled during heat waves. When it’s hot outside, birds struggle to learn, dogs bite more often, goat-like chamois pick fights. This is bad news not just for those who get on Fido’s toasted nerves. If the animals can’t stay alert enough to find food or avoid predators, their chances of survival go downhill, says Amanda Ridley, a behavioral ecologist at the University of Western Australia who coauthored the pied babbler study. 这项实验是日益增多的研究的一部分，这些研究表明，在热浪期间，动物的思维会变得混乱。当户外炎热时，鸟类难以学习新事物，狗咬人的频率增加，像山羊一样的岩羚羊（chamois）则会挑起争斗。这不仅对那些惹恼了“焦躁不安”的宠物狗的人来说是个坏消息。西澳大利亚大学的行为生态学家、该斑鸫鹛研究的合著者阿曼达·里德利（Amanda Ridley）表示，如果动物无法保持足够的警觉来寻找食物或躲避捕食者，它们的生存几率就会下降。
With climate change making heat waves more common, such cognitive impairments across the animal kingdom could ripple through entire ecosystems, putting already fragile species at greater risk. If pollinators forget which flowers to visit, crops and wild plants may fail. If birds can’t find food as easily, their young may not survive. And on a warming planet, a sharp mind is particularly vital. “A changing climate means that your ability to behaviorally adapt is even more important,” Ridley says. 随着气候变化使热浪变得更加频繁，整个动物界的这种认知障碍可能会波及整个生态系统，使本已脆弱的物种面临更大的风险。如果传粉者忘记了该访问哪些花朵，农作物和野生植物可能会减产。如果鸟类无法轻易找到食物，它们的幼崽可能无法存活。在一个变暖的星球上，敏锐的头脑尤为重要。里德利说：“气候变化意味着你进行行为适应的能力变得更加重要。”
Hotheaded
易怒的头脑
There is plenty of evidence that animals are affected by heat. Birds, for example, spend less time looking for food and feeding their young; they even sing less. Instead, they’ll sit around for hours with wings spread to dissipate the heat, and pant with their beaks wide open. Some animals retreat to shade or hide in cool burrows—again, skipping meals. Bees, meanwhile, splash their faces with droplets of water midflight when the weather is sizzling. This way, “they get convective cooling for their brain,” says Emily Baird, a neuroscientist at Stockholm University. 有大量证据表明动物会受到高温的影响。例如，鸟类花在寻找食物和喂养幼崽上的时间减少了；它们甚至减少了鸣叫。相反，它们会张开翅膀坐上几个小时以散热，并张大喙喘气。一些动物会退到阴凉处或躲进凉爽的洞穴中——这同样意味着错过进食。与此同时，当天气炎热时，蜜蜂会在飞行中用小水滴喷洒自己的脸部。斯德哥尔摩大学的神经科学家艾米丽·贝尔德（Emily Baird）说，通过这种方式，“它们能为大脑进行对流冷却。”
Some of the first hints that hot temperatures can mess up minds, however, came from studies on humans. Back in the 1800s, Belgian astronomer Adolphe Quetelet noticed that violent crime in France peaked in the summer. Later studies linked high temperatures with gun violence, mental-health-related hospital admissions, suicide, and gambling. When it’s hot, people have trouble making decisions, and their memory suffers. For students at schools without air conditioning, a school year just one degree Fahrenheit hotter reduces test scores by 1 percent, a study found. 然而，关于高温会扰乱思维的最早线索来自对人类的研究。早在19世纪，比利时天文学家阿道夫·凯特勒（Adolphe Quetelet）就注意到，法国的暴力犯罪在夏季达到顶峰。后来的研究将高温与枪支暴力、心理健康相关的住院治疗、自杀和赌博联系起来。天气炎热时，人们难以做出决定，记忆力也会下降。一项研究发现，对于在没有空调的学校上学的学生来说，学年气温每升高华氏1度，考试成绩就会下降1%。
Increasingly, there’s evidence that other species may also be more aggressive when mercury shoots up. A 2023 study that combed through nearly 70,000 reports of dogs biting people across eight US cities, from Chicago to Baltimore, found that such incidents were more likely to happen on hot, sunny, and smoggy days. The risk was 10 percent higher on a 90° F day than on a 60° F day—and not only because people are more apt to venture out for walks when the sun is shining (the researchers controlled for seasonal effects in their data). 越来越多的证据表明，当气温飙升时，其他物种也可能变得更具攻击性。2023年的一项研究梳理了从芝加哥到巴尔的摩等美国八个城市近7万份狗咬人报告，发现此类事件在炎热、阳光充足和雾霾天更容易发生。在华氏90度（约32摄氏度）的天气里，风险比华氏60度（约15摄氏度）的天气高出10%——这不仅仅是因为人们在阳光明媚时更倾向于外出散步（研究人员在数据中控制了季节性影响）。
Still, the scientists were unable to determine whether dogs get more aggressive as it gets hot, or if cranky humans provoke more attacks. “It’s likely that both humans and dogs get stressed and more irate at higher temperatures,” said Clas Linnman, a neuroscientist at the University of Miami and a coauthor on the study. And it’s not only dogs: A 2025 study out of China showed that many animals, including snakes and cats, are more inclined to bite people when it gets hot. 尽管如此，科学家们仍无法确定是狗在高温下变得更具攻击性，还是脾气暴躁的人类引发了更多的攻击。迈阿密大学的神经科学家、该研究的合著者克拉斯·林曼（Clas Linnman）表示：“很可能人类和狗在高温下都会感到压力并变得更加愤怒。”不仅是狗：2025年中国的一项研究表明，包括蛇和猫在内的许多动物在天气炎热时也更容易咬人。
Animals also seem to lose their cool with each other, especially if there is food involved. Scientists used binoculars and spotting scopes to spy on wild goat-like chamois that feed on protein-rich plants on the slopes of the Italian Apennine Mountains. More than 1,600 hours of observations over two summers revealed that when temperatures rose from 54° to 64° F, vegetation grew scarcer, and chamois aggression in turn shot up. The animals became territorial over patches of food, they assumed threatening postures, chased each other—attacks that, at times, escalated. 动物们似乎也会在彼此之间失去冷静，尤其是在涉及食物时。科学家们使用双筒望远镜和观测镜观察了意大利亚平宁山脉斜坡上以富含蛋白质的植物为食的野生岩羚羊。在两个夏季超过1600小时的观察中发现，当气温从华氏54度升至64度（约12至18摄氏度）时，植被变得稀疏，岩羚羊的攻击性随之飙升。这些动物为了争夺食物领地，摆出威胁姿态，互相追逐——这些攻击有时还会升级。
The small tropical fish called a golden julie also gets confrontational in the heat. Ordinarily, when a golden julie is placed in front of a mirror, it sees its reflected image as a stranger and shows some hostility, raising its fin, for example. But if the normally 78° water is raised to a hot 84°, the fish is more likely to get aggressive, and may bite and slap its tail against the mirror, as it tries to scare or attack the reflected image. 一种被称为“黄金朱莉”（golden julie）的小型热带鱼在高温下也会变得好斗。通常情况下，当黄金朱莉被放在镜子前时，它会将自己的倒影视为陌生人并表现出一定的敌意，例如竖起鱼鳍。但如果将通常华氏78度（约25摄氏度）的水温提高到华氏84度（约29摄氏度），这种鱼就更容易变得具有攻击性，并可能在试图恐吓或攻击倒影时，用尾巴拍打镜子。
Cognitive problems
认知问题
Heat waves can also hamper the ability of animals to learn, as Ridley and her colleagues observed with the southern pied babblers. In one of their experiments, the birds were presented with a simple wooden block with two holes drilled in it, each covered with a lid. If the bird pecked at the lid, it would rotate, revealing either an empty hole or a tasty mealworm (the babblers, Ridley says, “are highly motivated by mealworms”). One lid was dark, and the other a lighter shade of the same color. During heat waves, the birds needed twice as many trials to learn that the mealworm was always hidden under the lid of the same shade. 热浪还会阻碍动物的学习能力，正如里德利和她的同事在南部斑鸫鹛身上观察到的那样。在他们的一项实验中，鸟儿们面对一个简单的木块，上面钻有两个洞，每个洞都盖着盖子。如果鸟儿啄盖子，盖子就会旋转，露出一个空洞或一条美味的面包虫（里德利说，斑鸫鹛“对面包虫有很高的积极性”）。其中一个盖子颜色较深，另一个是同色系的较浅色调。在热浪期间，鸟儿需要两倍的尝试次数才能学会面包虫总是藏在相同颜色的盖子下。