What are waves?

# 5.1 Echolocation

The physics of waves extends into environmental science, with ocean waves, and biology, with the special use some animals make of them. One everyday use of waves relies on the physics of what happens after a wave meets an object and is reflected.

Think back to the times you heard a sound echo.

If you made the sound, then you would know that the longer the gap between the sound and the echo, then the further away the object that the sound was reflecting from. If you know the speed the sound wave is travelling at and the exact time it takes for the echo to be heard, then you can work out exactly how far away the object reflecting the sound is.

This is the principle of radar which is used to map and track the locations of aircraft in the sky and ships on the sea, in this case using electromagnetic waves. It is also the same principle used by ships that send a sonar (SOund Navigation And Ranging) pulse of sound into the ocean and ‘listen’ to the reflection to find out how deep the water is.

It is also the principle used by some animals to navigate and find their food.

Bottlenose dolphins can hear in the range 75 Hz to 150 kHz; they can also generate sounds in this frequency range and, by sensing the returning echo, they can become aware of both the shape of their environment – and their food (Figure 7).

Figure 7 A dolphin projects a series of clicks at different frequencies towards its prey. By sensing the returning echoes, it can determine the distance to its prey and environment.
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Other animals that commonly use ultrasound are the bats. These species show amazing diversity and mostly feed on insects – although some feed on fish, fruit, nectar and, in the case of the vampire bat, on mammalian blood. In flight, bats generate very short bursts of ultrasonic sound with their larynx that is emitted via the nose and mouth. Most bats have a nose shaped to focus the sound and some can even vary the width of the beam they project. From the returning echoes they can detect their prey and their environment.

It is amazing that both marine mammals and land animals have independently evolved a sonar navigation and feeding tool. Different species of bats have gone even further.

## Activity 1 Bats jamming bats

Allow approximately 30 minutes for this activity.

In this activity you will read a primary scientific research paper and a blog post. You will then answer some questions. Reading the primary paper and blog post will give you an insight into how scientists communicate their research to others.

The primary research paper was published in 2014 in the international journal Science. Science is published weekly by the American Association for the Advancement of Science (AAAS) and is a peer reviewed academic journal. Scientists communicate their research in articles in peer-reviewed academic journals. Peer review means that, before the article can be published, other academics in the same field review it for quality and accuracy. Not all articles submitted to peer-reviewed journals get published and it is not unusual for the reviewers to ask questions and suggest edits to the original paper before publication. Peer review acts as a form of self-regulation and provides credibility to the research published.

Blogs are regularly updated websites or webpages which are often run by individuals or small groups. They are not peer reviewed and are often written in a less academic and more conversational style.

The primary research paper is fairly technical but you will not have to remember the technical detail. Do look at the figures and note how the data are presented in graphical format. Select the link below to read the full Corcoran A.J. and Conner W.E. (2014) article and then select the link to the blog post by Ed Yong. You will then need to answer the questions that follow.

- Corcoran A.J. and Conner W.E. (2014) Bats jamming bats: Food competition through sonar interference, Science, vol. 346, no. 6210, pp. 745–747.
- Ed Yong a blog post in National Geographic’s Phenomena.

After doing this, answer the following questions based on your review.

1. What was the key finding of Corcoran and Conner in their paper published in Science?

## Answer

Mexican free-tailed bats (Tadarida brasiliensis) use a particular type of vocal ‘social calls’ or squeaks (sonar) to detect their prey. The sonar are echolocation signals. Corcoran and Conner discovered that these bats can block or ‘jam’ the sonar of other bats deliberately to stop their bat competitors from finding prey.

2. What additional information did Ed Yong’s blog post give about tiger moths and bats?

## Answer

Tiger moths can release ‘ultrasonic clicks’ which interfere with bats sonar and so divert the bats from a precise strike on the moths. The clicks protect the tiger moths from the attacking bats.

3. What differences did you notice between the Corcoran and Conner paper and Ed Yong’s blog post?

## Answer

There are quite a few differences between the two, some are listed below, but you may have noted other differences as well.

- The Corcoran and Conner paper uses more technical language, such as the Latin name for Mexican free-tailed bats (Tadarida brasiliensis), the blog post does not use technical language.
- The Corcoran and Conner paper is significantly longer than the blog post.
- The Corcoran and Conner paper has 3 technical figures which include graphs, the blog post has two photographs, one of a Mexican free tailed bat and the other of the Corcoran and Conner experimental set up.
- The Corcoran and Conner paper has an ‘abstract’ at the start and 22 references which are cited in the paper are listed at the end of the paper.

OpenLearn - What are waves?
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