Foster Russell G. - Seasons of life : the biological rhythms that enable living things to thrive and survive

Much has been written about the circadian clock. Foster and Kreitzman focus on the less familiar circannual clock, which governs responses to seasonal changes and tells animals when to mate, migrate or hibernate and plants when to grow and shed leaves. A complicated story but a joy to read. Financial Times

Seasons of Life is compelling. Beneath the litany of statistics and scientific evidence there is a profound awe of the subtle rhythms and invisible mechanisms of the natural world, knowledge that may prove vital in the coming years. P. D. Smith, Guardian

Readable and enlightening as the world has turned over millions of years, plants and animals have adapted to seasonal change and weather patterns. This might sound technical but in these authors hands, turns out to be deeply compelling. Jonathon Wright, Herald (Glasgow)

This tour-de-force addresses everything from feedback regulation of clock proteins to how migrating animals who navigate by the sun compensate for its apparent daily motion. The chapter on seasonal affective disorder helps explain our own winter trips. Elegant prose and clear diagrams make even the most complex physiology comprehensible. A must read for anyone who has ever looked up at a migrating skein of geese and wondered how do they know ? Adrian Barnett, New Scientist USA

RUSSELL FOSTER FRS is a Professor of Circadian Neuroscience, Chair of the Nuffield Laboratory of Ophthalmology and a Senior Kurti Fellow at Brasenose College at the University of Oxford. LEON KREITZMAN is a scientific writer and broadcaster, a widely respected futurologist and author of The 24 Hour Society. The authors also co-wrote Rhythms of Life which describes the rhythms of the daily cycle and was translated into five languages.

ALSO BY RUSSELL G. FOSTER AND LEON KREITZMAN

Rhythms of Life

The biological rhythms that enable living things to thrive and survive

Russell G. Foster & Leon Kreitzman

First published in Great Britain in 2009 by
PROFILE BOOKS LTD

3A Exmouth House

Pine Street

London EC1R 0JH

www.profilebooks.com

This eBook edition published in 2010

Copyright Russell G. Foster and Leon Kreitzman, 2009, 2010

The moral right of the authors has been asserted.

Typeset by MacGuru Ltd

This eBook is copyright material and must not be copied, reproduced, transferred, distributed, leased, licensed or publicly performed or used in any way except as specifically permitted in writing by the publishers, as allowed under the terms and conditions under which it was purchased or as strictly permitted by applicable copyright law. Any unauthorised distribution or use of this text may be a direct infringement of the authors and publishers rights and those responsible may be liable in law accordingly.

A CIP catalogue record for this book is available from the British Library.

eISBN 978 1 84765 279 9

Dedicated to the memory of
Professor Eberhard (Ebo) Gwinner
19382004

Founding director Max-Planck-Institut fr Ornithologie

He was not only one of the most influential ornithological researchers
of the second half of the twentieth century, but also a remarkable friend,
colleague and mentor (Brandstaetter & Krebs, 2004).

In their first book on biological time, entitled Rhythms of Life, Russell Foster and Leon Kreitzman told how cells measure the time of day with what is called a circadian clock. That truly remarkable clock has a periodicity of 24 hours and shows all the hallmarks of a watch devised by us humans. Each day the pips make sure that it keeps precisely in tune with the rotation of the earth and it is temperature compensated. Its role is to ensure that the myriad events of life occur in sequence each day. In this volume Seasons of Life they take us on to the story of how life adapts to changes of season. Those changes are dramatic indeed at the poles, and it is obvious that without great alterations life in these extreme regions would be impossible. That applies to a slightly lesser extent in the temperate zones but it is still critical to survive cold winters and hot summers, and to produce young at just that season of the year for them to survive to maturity. It comes as no especial surprise, therefore, that animals and plants not only have a daily clock but also possess a calendar that tells the organisms what time of year it is.

We understand much about the calendars involved but not yet enough. As this book shows, there are (at least) two sorts of calendar. One is based on circadian clocks and allows the organism to work out daylength, which is a sound proxy for time of year. If that is not remarkable enough, then the other way of measuring time surely is! Many organisms seem to possess a clock with an innate periodicity of about one year and, by analogy with the daily clock, it is called a circannual clock. How it is constructed is unknown but for animals that hibernate or spend their winters in the deep tropical forests away from changes in daylength, it offers a precise calendar.

That may be how organisms time the year, but this is where seasonality really starts to become intriguing. Virtually every process is best carried out at one time or other of the year and that is not something to take lightly. Survival depends on it, and transmitting ones genes into the next generation certainly does. Much of this book is devoted to the wonderful processes that occur seasonally. The most obvious examples are the migration of birds and large mammals to avoid unpleasant winters and yet who return with unerring accuracy the following year. The alternative strategy is to avoid inclement winters altogether by hibernation in rodents, diapause in insects, dormancy in plants. Finally one has to breed at that time when the young stand the best chance of themselves surviving to maturity. This is invariably determined by the availability of food for the newly born offspring, and so the seasonal cycles of many species become inextricably connected. This is where climate change is intruding into this carefully evolved system. Earlier springs cause caterpillar emergence to advance in Wytham Woods near Oxford, and so the great tits had better track these changes and advance the date of egg-laying or they will become extinct.

There is much more to seasonality, though, than breeding or migration. Virtually every internal process alters. Male red deer restrict food consumption quite drastically during Alpine winters as part of their survival strategy, even though, of course, they do not hibernate. This does not happen because food is absent, although one might imagine so. Take the deer down to lower altitudes and still it eats less.

We humans were clearly highly seasonal beasts until the coming of electric light but traces remain. So-called seasonal affective disorder (SAD) is an example, although as in so many stories one has to disentangle fact from supposition. Foster and Kreitzman attempt this and many other challenges in what is a wonderful story.

Sir Brian Follett FRS, Department of Zoology, University of Oxford

Several summers and autumns and winters and springs for that matter have passed since we first thought of writing this book. We tried the patience of family, friends and publishers but we managed to finish, with no small thanks to academic colleagues who reviewed our work with a critical eye.