New research has found that wells dug by wild horses in deserts provide valuable drinking water. This helps other animals too, as black bears and American badgers have been found drinking at the wells.

A team of researchers from Australia, Denmark and the US set up remote cameras at four desert locations in the US. Wild horses had used their feet to dig wells as much as two meters deep at these sites, so they could reach water under dry river beds and streams. The cameras were used to watch over the sites and were set to record whenever an animal moved in front of them.

The scientists saw plenty of comings and goings by horses but they were most interested in which other animals came to drink at the wells. Over the course of three summers, beginning in 2015, the team recorded 57 kinds of other large animals visiting the wells, including wild cats and deer. The team also found that the wells offered water to desert plants.

Researcher Erick Lundgren, from Aarhus University in Denmark, described the wild horses as “natural engineers”—animals that change the environment around them. Perhaps the best known natural engineers are beavers (河狸). Beavers cut down trees with their teeth, creating space in woods where sunlight can reach smaller plants and allow them to grow. Then beavers use the wood to create dams across rivers, which help clean pollution in water and protect their homes.

More than 12,000 years ago, several kinds of horse-related animals lived in North America but they all died out. Today’s wild horses develop from animals that were brought to America by humans in the past few hundred years. By digging wells that help other animals, they may be providing a similar service of natural engineering once given by their extinct relatives.

1.1. Why did the wild horses dig the wells?

A To protect themselves.

B To help other animals.

C To get drinking water.

D To create living space.

解析：选C。细节理解题，题干问 “野马挖井的原因”，定位第一段第一句 “wells dug by wild horses in deserts provide valuable drinking water” 及第二段第二句 “so they could reach water”，明确野马挖井是为了获取饮用水，选项 C 与原文一致；A “保护自己”、B “帮助其他动物”（是挖井的附加影响，非初衷）、D “创造生存空间” 均无原文依据。

2.2. What does Paragraph 2 mainly tell us about the study?

A The result.

B The method.

C The purpose.

D The problem.

解析：选B。段落主旨题，第二段主要介绍研究团队的做法：“set up remote cameras”“cameras were used to watch over the sites”，即研究的实施方法；A “结果” 对应第三段，C “目的” 未在该段体现，D “问题” 无相关表述，故选 B。

3.3. What can we learn about the wells?

A They were dug with horses’ teeth.

B They were found near running rivers.

C They reached as deep as four meters.

D They provided water for desert plants.

解析：选D。推理判断题，定位第三段最后一句 “The team also found that the wells offered water to desert plants”，与选项 D 完全一致；A “用牙齿挖掘” 错误（原文是 “used their feet”），B “在流动河流附近发现” 错误（原文是 “dry river beds”），C “深达四米” 错误（原文是 “as much as two meters deep”）。

4.4. What advantage can small plants get because of beavers?

A More sunlight.

B More water.

C Less pollution.

D Less space.

解析：选A。细节理解题，题干问 “小型植物从河狸身上获得什么好处”，定位第四段第三句 “creating space in woods where sunlight can reach smaller plants”，可知好处是获得更多阳光，选项 A 正确；B “更多水分”、C “更少污染” 是河狸筑坝对水的影响，D “更少空间” 与原文 “creating space” 相悖。

5.5. What is the main idea of the passage?

A Wild horses are changing deserts.

B Wild horses are natural engineers.

C Wild horses were brought to America.

D Wild horses were found visiting wells.

解析：选B。主旨大意题，文章核心围绕野马挖井惠及其他生物和环境展开，第四段明确将其定义为 “natural engineers”，后文进一步补充这一身份的合理性，选项 B 契合主旨；A “改变沙漠” 表述宽泛，C “被带到美洲” 是细节信息，D “造访水井” 偏离核心（核心是野马挖井）。