雅思阅读 076 — Extreme Heat Is Muddling Animals' Brains

改编自 Scientific American / Knowable Magazine（2026-06，Marta Zaraska）。

🎧 课文朗读音频（约 2 分钟）

Reading Passage

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.

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. If the animals can't stay alert enough to find food or avoid predators, their chances of survival go downhill.

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.

Hotheaded

There is plenty of evidence that animals are affected by heat. Birds 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. Bees, meanwhile, splash their faces with droplets of water mid-flight when the weather is sizzling. This way, "they get convective cooling for their brain," says Emily Baird, a neuroscientist at Stockholm University.

Some of the first hints that hot temperatures can mess up minds 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. For students at schools without air conditioning, a school year just one degree Fahrenheit hotter reduces test scores by one per cent.

Increasingly there's evidence that other species may also be more aggressive when the temperature shoots up. A 2023 study that combed through nearly 70,000 reports of dogs biting people across eight US cities found that such incidents were more likely on hot, sunny and smoggy days. The risk was ten per cent higher on a 90-degree day than on a 60-degree day.

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.

Animals also seem to lose their cool with each other, especially if there is food involved. Wild goat-like chamois in the Italian Apennines became more territorial and aggressive when temperatures rose and vegetation grew scarcer. The study authors predict that chamois aggression will go up 50 per cent by 2080 due to climate change.

Cognitive problems

Heat waves can also hamper the ability of animals to learn. In one experiment, southern pied babblers needed twice as many trials during heat waves to learn that a mealworm was always hidden under the lid of the same shade.

Zebra finches, pretty Australian songbirds, also have cognitive problems in the heat. When figuring out how to get a mealworm out of a see-through tube, they would just keep pecking on the tube — the bird equivalent of "banging your head against a brick wall."

For animals such as fish and insects that can't control their body temperature, heat waves could be particularly detrimental. "Changes in air temperature will affect brain temperature," says Baird. A hotter brain could hinder the functioning of nerves, which might affect sensing, memory and learning.

When Baird tried to teach bumblebees to associate sweet sugar water with the colour blue and bitter quinine with yellow, most learned the trick at 77 degrees Fahrenheit, but fewer than half managed to do so at 90 degrees. Such impaired cognition could spell trouble: if the insects forget which flowers to pollinate, not only will the pollinators suffer, but human agriculture too.

Questions

Questions 1–5: TRUE / FALSE / NOT GIVEN

1. On cooler days, southern pied babblers quickly learn to go around a plastic barrier.
2. Heat waves make birds sing more.
3. Students in schools without air conditioning score lower after a hotter school year.
4. Dog bite incidents are more likely on hot, sunny days.
5. Chamois aggression is expected to decrease by 2080.

Questions 6–10: Choose the correct letter, A, B, C or D.

6. In the babbler experiment, during heat waves the birds needed

   • A. half as many trials to learn
   • B. twice as many trials to learn
   • C. no trials to learn
   • D. three times as many trials

7. The dog bite study analysed reports from how many US cities?

   • A. 5
   • B. 8
   • C. 50
   • D. 70,000

8. On a 90-degree day, the risk of a dog bite is higher than on a 60-degree day by about

   • A. 5%
   • B. 10%
   • C. 50%
   • D. 90%

9. Zebra finches in the heat responded to a see-through tube by

   • A. going around it immediately
   • B. just pecking at it repeatedly
   • C. ignoring the mealworm
   • D. using their beaks to open it

10. What percentage of bumblebees learned the colour association at 90°F?

    • A. All of them
    • B. More than half
    • C. Fewer than half
    • D. None

Questions 11–13: Complete the sentences. Choose NO MORE THAN TWO WORDS.

11. Bumblebees splash water on their faces to get __________ cooling for their brain.
12. Chamois aggression is predicted to rise __________ per cent by 2080.
13. Animals that cannot control their body temperature are called __________.

Answers

1. TRUE
2. FALSE (天热时鸟叫得更少)
3. TRUE
4. TRUE
5. FALSE (预计上升50%)
6. B
7. B
8. B
9. B
10. C
11. convective
12. 50
13. ectothermic / cold-blooded (文中：can't control body temperature)

Glossary

• cognitive /ˈkɒɡnətɪv/ adj. 认知的
• heat wave 热浪
• predator /ˈpredətə/ n. 捕食者
• ecosystem /ˈiːkəʊsɪstəm/ n. 生态系统
• pollinator /ˈpɒlɪneɪtə/ n. 传粉者
• aggression /əˈɡreʃn/ n. 攻击性
• territory /ˈterətri/ n. 领地
• detrimental /ˌdetrɪˈmentl/ adj. 有害的
• ectothermic /ˌektəˈθɜːmɪk/ adj. 变温的