2021-12-12 10:57:00来源:网络


  Dolphins learn special foraging (觅食) techniques from their mothers—and it’s now clear that they can learn from their partners as well. Take the clever trick that some dolphins use to catch fish by trapping them in seashells. It turns out that they learn this skill by watching their fellows do the job. The discovery, reported in the journal Current Biology, helps reveal how groups of wild animals can transmit learned behaviors.

  “Dolphins are indeed very clever animals. So it makes sense that they are able to learn from others,” says Sonja Wild, a researcher at the University of Konstanz in Germany. She says young dolphins spend years in close association with their mothers and naturally tend to adopt their mothers’ ways, but this study shows that “dolphins are not only capable, but also motivated to learn from their peers.”

  They use a variety ways of finding food. Some dolphins, for example, use sponges (海绵 动物) as tools. The dolphins break a conical (圆锥形的) sponge off the seafloor, and then wear it almost like a protective cap on their long nose, or beak. This apparently helps them probe into the rough sand of the rocky seafloor and search for buried prey. Research done over a decade ago shows that this behavior gets passed down almost exclusively from mother to child. “So, at some point, one of the dolphins figured out how to use these sponges for foraging,” says Wild. After that, it was passed on to her descendants through the maternal line.

  Now, Wild and her colleagues have closely examined how dolphins learn another strategy for catching fish—one that involves using the empty shells of large sea snails. A dolphin will chase a fish into one of these shells, says Wild “and then they insert their beak into the shell, bring the whole thing up to the surface, and then shake it up above the water surface to drainthe water out of the shell until the fish basically falls into their open mouth.”

  “It’s a very remarkable behavior,” says Scott Witlin, one of Wild’s colleagues. “Seeing it is really sensational.” When he and Wild tracked which dolphins used this so-called “shelling” technique, they figured out that “the shelling behavior doesn’t spread between mother and offspring, but spreads between peers. “Being able to learn from peers may help animal populations survive in a changing environment. Because while knowledge from previous generations has been tested by time, certain behaviors may become less useful if conditions change,” Witlin said.

  46. What does the discovery published in the journal Current Biology reveal?

  A) The transmission modes of animals’ acquired behaviors.

  B) The changing trends of animals’ foraging techniques.

  C) The risk of extinction of rare wild animals.

  D) The unique foraging behaviors of dolphins.

  47. What does this study show about young dolphins?

  A) They observe where the prey often appears.

  B) They tend to invent their own manners to prey.

  C) They are stimulated to learn from their partners.

  D) They are the cleverest animals among mammals.

  48. What is the benefit of using sponges as tools for dolphins’ foraging?

  A) Helping them to search for buried prey.

  B) Protecting their long noses or beaks.

  C) Keeping them away from exposure.

  D) Softening the hurt by their predators.

  49. What are Wild and her colleagues currently researching about?

  A) How dolphins’ mothers pass down foraging practices to descendants.

  B) How environmental factors influence dolphin’s foraging behaviors.

  C) How dolphins acquire the ability of using the shelling behavior to catch fish.

  D) How the shelling technique transmits among other groups of wild animals.

  50. What did Scott Witlin say about dolphins’ learning behavior from their fellows?

  A) It contributes to dolphins’survival in unstable environment.

  B) It is a product of the evolution of the species of dolphins.

  C) It is impossible to happen among previous generations.

  D) It hinders the connection between mother and offspring.

  The forests of today will not be the forests of tomorrow. Rising temperatures, deforestation, development and climate-induced disasters are transforming the very makeup of Earth’s forests, new research published in the journal Science finds.

  Older, bigger trees—features in their respective ecosystems are withering away at an alarming rate, making the planet’s collective forests shorter and younger. The shift is being driven at different rates by different causes in different places, the study’s authors say, but the consequences will be global. Old growth forests absorb and store massive amounts of climate-warming carbon dioxide. They provide habitat for rare and critically endangered species and foster rich biodiversity. And they’re disappearing fast. Researchers found that the world lost roughly one-third of its old growth forest between 1900 and 2015. In North America and Europe, where more data was available, they found that tree mortality has doubled in the pas 40 years.

  Warming temperatures, wildfires, logging and insect outbreaks were among the many causes of the decline, says Nate McDowell, the study’s lead author. “Perhaps more concerning is that the track of all these disturbances are generally increasing over time and are expected to continue increasing into the future,” he says.

  McDowell, who works with the U.S. Department of Energy’s Pacific Northwest National Laboratory, is a tree physiologist by training. His focus is on how trees are affected by rising temperatures, arguably the biggest driver of forest change. To get a broader understanding of how forests are changing globally though, he brought in more than 20 other researchers with varying expertise. Together, they examined carefully more than 160 previous studies abouttree mortality and its global causes, applying current satellite data and modeling to create perhaps the most comprehensive look at Earth’s shifting forests to date.

  Just in the past year, the world has watched as massive wildfires tore across Siberia, the Amazon and Australia. Deforestation and illegal logging in Southeast Asia and Brazil continue at a intense pace. “Human-driven climate change is also making it difficult for many forests to fully recover from the type of natural disturbances—wind events, flooding or fire—that would normally occur, ” says McDowell. The researchers did find evidence that increased carbon dioxide in the atmosphere could increase tree growth in some places, but not to an extent where it would outweigh the harm being done by increased temperatures. The overriding (压倒一切的) trend was one of loss.

  “I would recommend that people try to visit places with big trees now, while they can, with their kids,” McDowell says. “Because there’s some significant threat, that might not be possible sometime in the future.”

  51. What can we learn from the new research published in the journal Science?

  A) The makeup of Earth’s forests is too complicated to be researched by human beings.

  B) Rising temperatures may cause the disastrous consequences to today’s forests.

  C) Forests play a critical part for humankind to survive and thrive on the earth.

  D) Climate-related disasters and human activities are changing the forest composition.

  52. What can we know about old growth trees?

  A) They are dying out at an amazing speed.

  B) Their mortality has tripled in recent years.

  C) Their disappearance are all caused by climate change.

  D) They are rich in North American and European areas.

  53. What is more concerning according to McDowell?

  A) Adverse factors to old forests’survival will continue to increase.

  B) Logging will cause the serious erosion of farmlands.

  C) The decline of older and bigger trees is inevitable.

  D) The increase of world population may double in twenty years

  54. What did McDowell partly do to get a broader understanding of how forests are changing


  A) Introduce many other well-known forest experts.

  B) Investigate previous studies about trees’ growth.

  C) Enrich his own expertise on forests.

  D) Apply existing satellite information.

  55. What does McDowell say about human-driven climate change?

  A) It has an overwhelming influence on Earth’s shifting forests.

  B) It plays a leading role in bringing about massive wildfires.

  C) It adds complexity to the forests’ recovery from natural disasters.

  D) It needs easing through joint efforts of authorities and the public.

  答案:46. A 47. C 48. A 49. C 50. A

  51. D 52. A 53. A 54. D 55. C



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