雅思阅读 017 · Extreme Heat Is Muddling Animals' Brains

改编自 Scientific American（Marta Zaraska, 2026）。题型：T/F/NG + 填空 + 选择题。难度：中等偏上（Passage 2，约 900 词）。

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🎧 课文朗读音频（约 1 分钟）

正文 Passage

On a blazing hot day in South Africa, female southern pied babblers cannot 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 quickly figure out that all they have to do is go around the small plastic wall. But when the temperature rises, 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 is 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 a dog's toasted nerves. If the animals cannot stay alert enough to find food or avoid predators, their chances of survival decline, says Amanda Ridley, a behavioural ecologist at the University of Western Australia.

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 cannot find food as easily, their young may not survive. "A changing climate means that your ability to behaviourally adapt is even more important," Ridley says.

Hot-headed

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 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 splash their faces with droplets of water midflight when the weather is sizzling, which gives them convective cooling for their brain.

Some of the first hints that hot temperatures can disrupt 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. When it is 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 one per cent.

Increasingly, there is evidence that other species may also be more aggressive when temperatures rise. 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 not only because people are more likely to go for walks when the sun is shining.

It is 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. And it is not only humans and domestic animals. Scientists observing wild goat-like chamois in the Italian Apennines found that when temperatures rose, vegetation grew scarcer and chamois aggression shot up. The animals became territorial over patches of food, assumed threatening postures and chased each other. The study authors predict that chamois aggression will rise 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, the southern pied babblers were presented with a simple wooden block with two holes, each covered with a lid of a different shade. 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.

Another group tested zebra finches and discovered that when temperatures are high, they too have cognitive problems. When figuring out how to get a mealworm out of a transparent tube, they just keep pecking on the tube — the bird equivalent of banging your head against a brick wall.

More recently, researchers found that male guppies also have trouble getting through a maze after spending several days in heat-wave-like water, even if the prize for getting it right is a female.

For animals such as fish and insects that cannot control their body temperature, heat waves could be particularly detrimental. "Changes in air temperature will affect brain temperature," says Emily Baird, a neuroscientist at Stockholm University. A hotter brain could hinder the functioning of nerves, and that might affect sensing, memory and learning.

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

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题目 Questions

Questions 1-5: T/F/NG

1. On cooler days, pied babblers can solve the barrier problem quickly.

2. Climate change is making heat waves less frequent.

3. Birds sing more during heat waves.

4. Quetelet's 19th-century study found that violent crime peaked in winter.

5. Dogs are more likely to bite people on hot days.

Questions 6-10: Complete the notes below. Choose NO MORE THAN TWO WORDS.

• Chamois became (6) ____________ over patches of food when temperatures rose.
• The study predicts chamois aggression will rise (7) ____________ by 2080.
• During heat waves, babblers needed (8) ____________ as many trials to learn the task.
• Zebra finches kept pecking at the (9) ____________ instead of solving the task.
• Bumblebees that learned the sugar-blue association were fewer than half at (10) ____________.

Questions 11-13: Choose the correct letter.

11. Why is heat particularly harmful for fish and insects?

• A. they cannot control their body temperature
• B. they have no brains
• C. they live in water
• D. they are too small

12. Baird's research suggests that hot temperatures affect:

• A. only birds
• B. sensing, memory and learning
• C. only humans
• D. plant growth

13. The passage overall suggests that climate change:

• A. has no effect on animal behaviour
• B. impairs animal cognition and could harm ecosystems
• C. makes animals smarter
• D. only affects humans

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答案 Answers

题号	答案	定位
1	TRUE	"On cooler days, the birds quickly figure out..."
2	FALSE	"making heat waves more common"
3	FALSE	"they even sing less"
4	FALSE	"peaked in the summer"
5	TRUE	"such incidents were more likely on hot... days"
6	territorial	"became territorial over patches of food"
7	50 per cent	"rise 50 per cent by 2080"
8	twice	"needed twice as many trials"
9	tube	"just keep pecking on the tube"
10	90 degrees	"fewer than half... at 90 degrees"
11	A	"fish and insects that cannot control their body temperature"
12	B	"might affect sensing, memory and learning"
13	B	全文主旨

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核心词汇

heat wave / cognitive / impairment / pollinator / predator / aggression / territorial / trial / babbler / zebra finch / guppy / bumblebee / dissipate / burrow / detrimental / neuro / memory / learning