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  • Key Stage 3
  • GCSE
  • Popular Activity
  • Topical

Type: Activity
Learning Strategy: Data work
Topic: Feeding relationships

This is part of our 'Classics Collection'. For new GCSE activities with up-to-date contexts, see upd8 Crucial.

International pest control experts have exterminated 10,000 rats on the small Hebridean Island of Canna. The operation cost half a million pounds but conservationists consider this money well spent. The rats are recent invaders. They arrived by boat as stow-aways and really made themselves at home. Their population exploded. In this modeling activity, students learn why rat invasions are bad news for birds and why these rodents are less of a problem on the mainland.

We are grateful to Richard King of The Queen Katherine School, Cumbria for use of the rat_files spreadsheet.

Published: 2nd March 2006
Reviews & Comments: 16

Learning objectives

Students will
-explain how population size depends on resources
-use a computer program to model changes

Try the activity

You will need Acrobat Reader installed to open the activity sheets.

Predator-prey interactions.

11 - 14 (KS3)
Ecological relationships QCA 8d:
How do living things in a community depend on each other?
• explain population data in terms of predator-prey interdependence and intra-species competition

GCSE specifications
AQA Core Science
Unit B1b Evolution and Environment: 11.5 What determines where particular species live and how many of them are there?
• To survive, organisms require a supply of materials from their surroundings and from the other living organisms there.
Edexcel Core Science
Unit B1a Topic 1:Environment
• Explain population data in terms of predator-prey interdependence and intra-species competition.
Gateway Core Science
Module B2 Understanding our environment: Item: B2d: Compete or Die.
• Explain how the size of a predator population will affect the numbers of prey and vice versa.
Twenty First Century Core Science
Module B3 Life on Earth: B3.4 Why do some species become extinct, and does it matter?
• Relate changes affecting one species in a food web to the impact on other
species that are part of the same food web.

Running the activity

Page 1 sets the context by asking what could wipe out populations of birds. Likely suggestions are lack of food, disease, predators or habitat destruction.
Page 2 reveals that rats cause more bird extinctions than any other factor. Students model the growth of a rat population and consider why the rodent's numbers do not increase so fast on the mainland. Students could discuss reasons for the difference in small groups. Access to an abundant food supply is one factor, but the lack of predators is also important. On the mainland, rats are prey to owls and cats. Only 1 in10 survives. The long-term interactions between populations of rats and owls can be modelled using the rat_files spreadsheet. The model assumes that the rats and owls are on a small island with a carrying capacity of 200 rats. The rat population will crash if it exceeds 200. Page 3 guides the investigation and asks students to predict what effect cutting the numbers of stray cats will have on local rat populations.

Further information

The spreadsheet plots rat and owl numbers over the next 50 years and includes a macro. If the security level in Excel is set to high, the graphs will not plot. To allow the macro to run: close the file, choose macro from the tools menu, set to medium or low and then reopen the file. If student log-ins are controlled by Ranger, Classlink or similar software, this will need to be done by the network manager.

News links

Video clips of rats swimming and eating bird's eggs.
A news item about rat eradication on Canna.
An excellent two page summary of the problems caused by alien invasive species like rats can be downloaded from this site.
Rat populations can soar if an increased food supply becomes available. This report looks at the problems that can occur where there is a high concentration of fast food outlets.
New Scientist
The threat rats pose to the Galapagos Islands.
Download a simple spreadsheet to explore the effects of competition and predation.
News item on the recovery of bird populations following removal of the rats.

Reviews & Comments

Write your online review to share your feedback and classroom tips with other teachers. How well does it work, how engaging is it, how did you use it, and how could it be improved?


Jun 7th, 2012

1 Star

Could not use the resource. The activity sheet did not download. When I tried to click on it the page just refreshed.

Reviewer: Peter Fisherf

Rats review

Jun 18th, 2009

4 Star

Worked quite well with my low ability year 10's. I had to complete some of the tables for them in advance so that they could cope with the maths involved though.

Reviewer: Rachel Minton

Bears in trouble

Mar 2nd, 2009

5 Star

I did this activity with a low ability year 8 and it workedreally well, i stretched it out over 2 lessons and then they presented their findings as a news reporter for newsround (with a video to film themselves). The pupils really enjoyed the activity and thought of themselves as ecologists!

Reviewer: Sarah Penny


Jun 18th, 2008

5 Star

I have used this activity for middle ability and high ability year 10 classes, adapting the amount of guidance provided for calculations accordingly.

I asked the class why birds fly to remote islands in the first place, and then why they think so many birds have been wiped out there recently. Once I they suggested rats, I showed a couple of video clips of rats from which they really enjoyed - clips of a rat eating an egg; baby rats; young rats; and an overview of brown rats.

Both classes especially engaged with the graph of rat / owl population dynamics, and I would say that this is a great opportunity to pull together their understanding of many topics within ecology.

This is a great resource!

Reviewer: Anthony Jackson


May 20th, 2008

5 Star

I have just delivered the Rats lesson to my lower ability group in Y10. They really got into it - especially the excel activity.

Reviewer: Juliette Thomas


Feb 8th, 2008

5 Star

I really liked this one - especially the excel file to help with the graph plotting. My students were able to see it using a multimedia projector and it was useful for class discussion.

Reviewer: Carol Pratt


Jul 6th, 2007

4 Star

Plan to use this week with year 9. I think it will go down well, especially with the computer programmes-hope the school computer will accept the macros as it looked invaluable for the students to play with!

Reviewer: f m


Jul 4th, 2007

3 Star

eXCELLENT until we tried the macro which did not work, would have been a good lesson for my school which has linited computers, for me to be ablr to use the model on the interactive board and show the whole class.
very stimulating tho....

Reviewer: Joanna Hinds

enabling macros

Feb 24th, 2007

5 Star

To enable macros go to Tools, Macros, Security and select the level of security medium. Reload file and when a dialog box prompts select enable macros. That's all you need to do to start using this excellent modelling spreadsheet.

Reviewer: Lucho Corrales


Oct 25th, 2006

2 Star

Looks good if only I could do the modelling bit by enabling the Macros - anyone with nay advice??

Reviewer: Anne Maingay

reason for macro problem?

Sep 5th, 2006

3 Star

Looks like a good activity, but macros on spreadsheet don't run due to our firewall software. I'm going to quiz my IT expert husband, but it is something that the other people with problems may wish to check.

Reviewer: Sarah Lewins

Works without technology!

Apr 13th, 2006

5 Star

Used this in an old fashioned (no IT at all) classroom with lowish Y10 class at the end of a lesson about food chains - even though they had to do the calcluations be hand (calculator) it worked very well! Thanks

Reviewer: Simon Hepburn

Population control

Mar 26th, 2006

5 Star

I was very impressed!
I'm afraid I managed to download the whole thing with no problem. I also added a sheet to the excel file to show the answers calculated for a whole year with an accompanying graph that soared to 64,000 rats in a year! This led onto discussion as to why this could never really happen and so into the rest of the spreadsheet.

Reviewer: Ben Lovick

Rat files

Mar 21st, 2006

5 Star

Great model. You have to log in using your UPD8 username and password to be able to download the Excel file, otherwise it tries to do it as a Word file.

Reviewer: Louise McLaren


Mar 12th, 2006

5 Star

Unable to open or save. Disaappointed as it would fit in well with the BTEC course we propose to run in Sept. Any suggestions.
PS i love the upd8 scenarios, I have used many in my KS3 and hope to use them in BTEC courses next year. Keep producing this incredibly valuable teaching resource.

Reviewer: Linda Worrall


Mar 7th, 2006

5 Star

Looks good but unable to use macros. This is disappointing

Comment from UPD8 Team:

Sorry to hear that the macros didn't work on your machine. I have tried downloading the spreadsheet and the macros worked fine on my pc which runs on Windows 2000. This has been similarly tested by colleagues at the ASE. We
can only suggest that it might be due to the version of Windows that you are running on your computer?

Reviewer: David Ford

The upd8 store
200 lessons and assessments from as little as £4.95

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