# Reasons for Mass Strandings of Whales and Dolphins: answers and explanations

Cambridge IELTS 9, Test 1, Listening Part 4

Source: Recording, questions and answer key from Cambridge IELTS 9, Test 1, 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 | tide | where sometimes the tide goes out suddenly, confusing the animals. |
| 32 | hearing | a type of worm is commonly found in the ears of dead whales. ... Since marine animals rely heavily on their hearing to navigate, |
| 33 | plants and animals | Many toxins, as I'm sure you're aware, originate from plants or animals. |
| 34 | feeding | most had not been feeding as they stranded. |
| 35 | noise | A growing concern is that loud noises in the ocean cause strandings. ... Noises such as those caused by military exercises are of particular concern |
| 36 | healthy | For one, all the stranded animals were healthy. |
| 37 | group | the animals were spread out along 38 km of coast. ... Whereas it's more common for the animals to be found in a group when mass strandings occur. |
| 38 | social | since the whales that are thought to be most social, the toothed whales, ... are the group that strand the most frequently. |
| 39 | leader | Examination of the dead animals revealed that apart from the leader. ... All the others had been healthy at the time of their death. |
| 40 | network | if you're interested in finding out more about these networks or establishing one yourself. |

## Why these answers are right

**31. tide.** The notes say strandings are common where something can change quickly. The lecturer says that in some of the locations the tide goes out suddenly, confusing the animals, so tide is the feature that changes fast.

**32. hearing.** Under parasites, the notes ask what parasites can affect that the animals depend on for navigation. The lecturer says worms are found in whales' ears and that marine animals rely heavily on their hearing to navigate, so hearing fits.

**33. plants and animals.** The gap names the sources of the poisons whales consume. The lecturer says many toxins originate from plants or animals and that whales take them in through normal feeding, so plants and animals, in either order, fills the gap.

The why and the trap for questions 34 onwards are free with an account on the [answers page](https://testmigo.com/ielts/listening/reasons-for-mass-strandings-of-whales-and-dolphins/answers).

## Transcript

**Announcer:** Section 4.

**Announcer:** You will hear part of a lecture about a problem related to the behavior of certain sea creatures.

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

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

**Speaker:** Good afternoon everyone.

**Speaker:** Well, with some of you about to go out on fieldwork, it's timely that in this afternoon's session, I'll be sharing some ideas about the reasons why groups of whales and dolphins sometimes swim ashore from the sea,

**Speaker:** right onto the beach, and most often die in what are known as 'mass strandings'.

**Speaker:** Unfortunately,

**Speaker:** this type of event is a frequent occurrence in some of the locations that you'll be traveling to, where sometimes the tide goes out suddenly, confusing the animals.

**Speaker:** However, there are many other theories about the causes of mass strandings.

**Speaker:** The first is that the behavior is linked to parasites.

**Speaker:** It's often found that stranded animals were infested with large numbers of parasites.

**Speaker:** For instance, a type of worm is commonly found in the ears of dead whales.

**Speaker:** Since marine animals rely heavily on their hearing to navigate,

**Speaker:** this type of infestation has the potential to be very harmful.

**Speaker:** Another theory is related to toxins or poisons.

**Speaker:** These have also been found to contribute to the death of many marine animals.

**Speaker:** Many toxins, as I'm sure you're aware, originate from plants or animals.

**Speaker:** The whale ingests these toxins in its normal feeding behavior, but whether these poisons directly or indirectly lead to stranding and death seems to depend upon the toxin involved.

**Speaker:** In 1988, for example, 14 humpback whales examined after stranding along the beaches of Cape Cod were found to have been poisoned after eating tuna that contained saxitoxin.

**Speaker:** The same toxin that can be fatal in humans.

**Speaker:** Alternatively, it has also been suggested that some animals strand accidentally by following their prey ashore in the confusion of the chase, in 1995 David Thurston monitored pilot whales that beached after following squid ashore.

**Speaker:** However, this idea does not seem to hold true for the majority of mass strandings.

**Speaker:** Because examination of the animals' stomach contents revealed that most had not been feeding as they stranded.

**Speaker:** There are also some new theories which link strandings to humans.

**Speaker:** A growing concern is that loud noises in the ocean cause strandings.

**Speaker:** Noises such as those caused by military exercises are of particular concern, and have been pinpointed as the cause of some strandings of late.

**Speaker:** One of these, a mass stranding of whales in 2000 in the Bahamas coincided closely with experiments using a new submarine detection system.

**Speaker:** There were several factors that made this stranding stand out as different from previous strandings.

**Speaker:** This led researchers to look for a new cause.

**Speaker:** For one, all the stranded animals were healthy.

**Speaker:** In addition, the animals were spread out along 38 km of coast.

**Speaker:** Whereas it's more common for the animals to be found in a group when mass strandings occur.

**Speaker:** A final theory is related to group behavior, and suggests that sea mammals cannot distinguish between sick and healthy leaders, and will follow sick leaders.

**Speaker:** Even to an inevitable death.

**Speaker:** This is a particularly interesting theory, since the whales that are thought to be most social, the toothed whales,

**Speaker:** are the group that strand the most frequently.

**Speaker:** The theory is also supported by evidence from a dolphin stranding in 1994.

**Speaker:** Examination of the dead animals revealed that apart from the leader.

**Speaker:** All the others had been healthy at the time of their death.

**Speaker:** Without one consistent theory, however, it is very hard for us to do anything about this phenomenon, except to assist animals where and when we can.

**Speaker:** Stranding networks have been established around the world to aid in rescuing animals and collecting samples from those that could not be helped.

**Speaker:** I recommend John Connor's Marine Mammals Ashore.

**Speaker:** As an excellent starting point, if you're interested in finding out more about these networks or establishing one yourself.

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

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

[Practice Reasons for Mass Strandings of Whales and Dolphins](https://testmigo.com/ielts/listening/reasons-for-mass-strandings-of-whales-and-dolphins)