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Konrad Lorenz wrote engagingly of the antics of his ducks and geese. Now biomathematicians write computer programs on the costs and benefits of fighting over food or travelling in search of other prey. It鈥檚 all part of the growing science of animal behaviour, summarised neatly for students by Mark Ridley (Animal Behavior, 2nd edition, Blackwell Scientific, 拢16.50, ISBN 0 86542 390 3). An excellent, clear introduction with plenty of good illustrations.