Did you know that Tasmanian hens have two husbands? That vampire bats will share food with hungry fellow bats and that Hanuman langurs commit infanticide? Why creatures great and small behave in such fascinating and seemingly perplexing ways is explained in this delightful account of the evolutionary foundations of animal social behaviour. Illustrated with both photographs and explanatory diagrams, this expert and inviting tour of the social world of animals will inform and charm anyone curious about the motivations behind the amazing range of activity in the animal kingdom.