# Research on the Tool-using Skills of New Caledonian Crows: answers and explanations

The Official Cambridge Guide to IELTS, Test 8, Listening Part 4

Source: Recording, questions and answer key from The Official Cambridge Guide to IELTS, Test 8, Listening Part 4. © Cambridge University Press & Assessment. Used for educational practice. Explanations and evidence notes are written by Testmigo.

## Answer key

| Q | Answer | Proof |
| --- | --- | --- |
| 31 | hook | bent some straight wire into a hook |
| 32 | string | the crows first had to pull up a string to get a short stick |
| 33 | danger | possibly to assess whether or not they present a danger. |
| 34 | rubber | One involved a rubber snake. |
| 35 | light | Pierre used a short piece of woodchip to touch a light which was flashing |
| 36 | intelligence | a major difficulty is assessing whether this tool-using behavior is a sign of intelligence. |
| 37 | tail | So the researchers have attached tiny cameras to the tails of some birds, |
| 38 | energy | It's possible that the birds can derive so much energy from these grubs that they only need to eat a few each day. |
| 39 | chemical | The beetle larvae have a distinct chemical makeup |
| 40 | diet | Scientists have collected samples from crows in order to estimate the proportion of larvae in their diet. |

## Why these answers are right

**31. hook.** Betty made something out of wire to move a food bucket. The lecturer says she bent some straight wire into a hook and used it to lift a small bucket of her favorite food from a vertical pipe, so hook names the object she made.

**32. string.** In the first of the three stages, the crows had to move something to get the short stick. The lecturer says they first had to pull up a string to get a short stick, so string is the answer; the toolbox held the long stick.

**33. danger.** The note asks what the crows checked an object for. In the Oxford experiments, crows used sticks to inspect all sorts of objects, possibly to assess whether or not they presented a danger, so danger fits after any.

The why and the trap for questions 34 onwards are free with an account on the [answers page](https://testmigo.com/ielts/listening/research-on-the-tool-using-skills-of-new-caledonian-crows/answers).

## Transcript

**Announcer:** You will hear a lecture about a species of bird called the New Caledonian crow.

**Announcer:** First, you have some time to look at questions 31 to 40.

**Announcer:** Now listen carefully and answer questions 31 to 40.

**Speaker:** I'm going to talk today about research into a particular species of bird, the New Caledonian crow, whose natural habitat is small islands in the Pacific Ocean.

**Speaker:** And it seems that these crows are exceptionally resourceful.

**Speaker:** Using sticks or other tools to find food isn't unknown among birds and animals.

**Speaker:** Some chimpanzees for example are known to bang nuts on stones in order to break the shell and get at the edible kernel inside.

**Speaker:** One New Caledonian crow, called Betty,

**Speaker:** bent some straight wire into a hook, and used it to lift a small bucket of her favorite food from a vertical pipe.

**Speaker:** This experiment was the first time she'd been presented with wire.

**Speaker:** Which makes it very impressive.

**Speaker:** Another crow called Barney has demonstrated his skill at using sticks to forage for food.

**Speaker:** In one research project, scientists from New Zealand and Oxford set captive New Caledonian crows a three-stage problem.

**Speaker:** If they wanted to extract food from a hole, the crows first had to pull up a string to get a short stick, then use that short stick to remove a long stick from a toolbox.

**Speaker:** And finally, use the long stick to reach the food.

**Speaker:** Amazingly, they worked out how to do this successfully.

**Speaker:** Further experiments carried out at Oxford suggest that crows can also use sticks as tools to inspect all sorts of objects, possibly to assess whether or not they present a danger.

**Speaker:** The idea for the experiment came from observing the birds using tools to pick at random objects, such as a picture of a spider that was printed on some cloth.

**Speaker:** In this research, five pairs of crows, including Barney, underwent tests to see how they would react to a variety of objects.

**Speaker:** Which were carefully chosen, so the birds wouldn't be tempted to view them as a possible source of food.

**Speaker:** As a further precaution, all the crows had been fed beforehand.

**Speaker:** On eight occasions, a bird's first contact was by using a tool.

**Speaker:** In all three trials, Barney began by using a stick for inspection.

**Speaker:** One involved a rubber snake.

**Speaker:** First he approached it, but didn't touch it.

**Speaker:** Then retreated to pick up a stick.

**Speaker:** He then prodded it with the stick.

**Speaker:** After some more investigation, he discarded the stick and carried on pecking at the snake more confidently.

**Speaker:** Apparently convinced that it wouldn't move.

**Speaker:** In other experiments, two different birds called Pierre and Corbeau, also made a first approach with tools on three separate occasions.

**Speaker:** Pierre used a short piece of woodchip to touch a light which was flashing, and Corbeau was seen prodding a metal toad with a stick.

**Speaker:** Significantly, the crows tended to use the sticks only to make their first contact with the object.

**Speaker:** Subsequently, they either ignored the object or dropped the tool and pecked at the object.

**Speaker:** Which is very different from using the tool to get access to food.

**Speaker:** So, what conclusions can be drawn from the research?

**Speaker:** Evidence is building up from experiments such as these that the birds are able to plan their actions in advance.

**Speaker:** Which is very interesting for understanding their cognition.

**Speaker:** They don't seem to be responding in a pre-programmed sort of way.

**Speaker:** It may even be possible that they're able to view a problem and work out what the answer is.

**Speaker:** However, a major difficulty is assessing whether this tool-using behavior is a sign of intelligence.

**Speaker:** To some extent, this is related to the ecological circumstances in which the animal is found.

**Speaker:** So, scientists want to find out much more about how the crows behave in their native habitat.

**Speaker:** And a team from Exeter and Oxford universities is carrying out research in New Caledonia.

**Speaker:** They're looking into whether the birds' way of searching for food gives them any possible evolutionary advantage.

**Speaker:** The birds are hard to observe, as they live in a region of mountainous forest.

**Speaker:** So the researchers have attached tiny cameras to the tails of some birds,

**Speaker:** as one method of investigating their behavior.

**Speaker:** The birds are masters at using sticks to find their food, in particular beetle larvae from the trees.

**Speaker:** It's possible that the birds can derive so much energy from these grubs that they only need to eat a few each day.

**Speaker:** This would mean that they wouldn't have to spend most of their waking time searching for food,

**Speaker:** as most animals do.

**Speaker:** The beetle larvae have a distinct chemical makeup, which can be traced through the feathers and blood of birds that eat them.

**Speaker:** Scientists have collected samples from crows in order to estimate the proportion of larvae in their diet.

**Speaker:** They should then be able to gauge the extent to which individual birds depend on using sticks to feed themselves.

**Speaker:** We have learned a great deal about the ability of New Caledonian crows to use tools, and some very interesting research is being carried out into them.

**Announcer:** That is the end of section 4.

**Announcer:** You now have half a minute to check your answers.

[Practice Research on the Tool-using Skills of New Caledonian Crows](https://testmigo.com/ielts/listening/research-on-the-tool-using-skills-of-new-caledonian-crows)