Ever wondered why rats, mice and squirrels seem to reproduce at such an alarming rate? Rodents are among the most successful of all the mammal groups. In this unit you will learn more about some of the evolutionary features that make these creatures so plentiful. To get the most out of this unit you will need access to a copy of The Life of Mammals (2002) by David Attenborough, BBC Books (ISBN 0563534230), and The Life of Mammals (2002) on DVD, which contains the associated series of BBC TV programmes. This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.