Pheromones have been found in species in almost every part of the animal kingdom, including mammals. Pheromones (a molecule or defined combination of molecules) are species-wide signals which elicit innate responses (though responses can be conditional on development as well as context, experience, and internal state). In contrast, signature mixtures, in invertebrates and vertebrates, are variable subsets of molecules of an animal's chemical profile which are learnt by other animals, allowing them to distinguish individuals or colonies. All signature mixtures, and almost all pheromones, whatever the size of molecules, are detected by olfaction (as defined by receptor families and glomerular processing), in mammals by the main olfactory system or vomeronasal system or both. There is convergence on a glomerular organization of olfaction. The processing of all signature mixtures, and most pheromones, is combinatorial across a number of glomeruli, even for some sex pheromones which appear to have 'labeled lines'. Narrowly specific pheromone receptors are found, but are not a prerequisite for a molecule to be a pheromone. A small minority of pheromones act directly on target tissues (allohormone pheromones) or are detected by non-glomerular chemoreceptors, such as taste. The proposed definitions for pheromone and signature mixture are based on the heuristic value of separating these kinds of chemical information. In contrast to a species-wide pheromone, there is no single signature mixture to find, as signature mixtures are a 'receiver-side' phenomenon and it is the differences in signature mixtures which allow animals to distinguish each other.

We are entering one of the most exciting periods in the study of chemical communication since the first pheromones were identified some 40 years ago. This rapid progress is reflected in this book, the first to cover the whole animal kingdom at this level for 25 years. The importance of chemical communication is illustrated with examples from a diverse range of animals including humans, marine copepods, Drosophila, Caenorhabditis elegans, moths, snakes, goldfish, elephants and mice. It is designed to be advanced, but at the same time accessible to readers whatever their scientific background. For students of ecology, evolution and behaviour, this book gives an introduction to the rapid progress in our understanding of olfaction at the molecular and neurological level. In addition, it offers chemists, molecular and neurobiologists an insight into the ecological, evolutionary and behavioural context of olfactory communication.

As humans are mammals, it is possible, perhaps even probable, that we have pheromones. However, there is no robust bioassay-led evidence for the widely published claims that four steroid molecules are human pheromones: androstenone, androstenol, androstadienone and estratetraenol. In the absence of sound reasons to test the molecules, positive results in studies need to be treated with scepticism as these are highly likely to be false positives. Common problems include small sample sizes, an overestimate of effect size (as no effect can be expected), positive publication bias and lack of replication. Instead, if we are to find human pheromones, we need to treat ourselves as if we were a newly discovered mammal, and use the rigorous methods already proven successful in pheromone research on other species. Establishing a pheromone relies on demonstration of an odour-mediated behavioural or physiological response, identification and synthesis of the bioactive molecule(s), followed by bioassay confirmation of activity. Likely sources include our sebaceous glands. Comparison of secretions from adult and pre-pubertal humans may highlight potential molecules involved in sexual behaviour. One of the most promising human pheromone leads is a nipple secretion from the areola glands produced by all lactating mothers, which stimulates suckling by any baby not just their own.

Pheromones and Animal Behavior Chemical Signals and Signatures SECOND EDITIONPheromones and other kinds of chemical communication underlie the behavior of all animals. Building on the strengths of the first edition, widely recognized as the leading text in the subject, this is a comprehensive overview of how pheromones work.Extensively revised and expanded to cover advances made over the last ten years, the book offers a thorough exploration of the evolutionary and behavioral contexts of chemical communication, along with a detailed introduction to the molecular and neural basis of chemosensory perception. At a time of ever increasing specialization, Wyatt offers a unique synthesis, integrating examples across the animal kingdom. A final chapter critically considers human pheromones and the importance of olfaction to human biology. Its breadth of coverage and readability make the book an unrivaled resource for students and researchers in a range of fields from chemistry, genetics, genomics, molecular biology, and neuroscience to ecology, evolution, and behavior.A full list of the references from this book is available for download from www.cambridge. org/pheromones. Preface page xi Acknowledgments xv List of SI prefixes xvi List of abbreviations xvii 1 Animals in a chemical world 1 1.1 Intra-specific semiochemicals: pheromones and signature mixtures 2 1.2 "Innateness" of pheromones 16 1.3 How pheromone signals evolve from chemical cues 18 1.4 Pheromone diversity, specificity, and speciation 24 1.5 Production of pheromones 31 1.6 Pheromones: signal honesty and costs 32 1.7 Chemical profiles from which signature mixtures are learned for individual and colony recognition 37 1.8 Differences in response to pheromones 43 1.9 Releaser and primer effects of pheromones 43 1.10 Multimodal signals 44 1.11 Allohormone pheromones bypassing olfaction and taste 45 1.12 Pheromones and signature mixtures in humans? 45 1.13 Pollution disrupts chemical communication in aquatic organisms 45 Summary 46 Further reading 48 2 Methods for identifying and studying semiochemicals 49 2.1 Bioassays 49 2.2 Collection and analysis of semiochemicals 55 2.3 Using genetic and other techniques from molecular biology 59 Summary 63 Further reading 63 3 Pheromones, chemical cues, and sexual selection 65 3.1 Which sex should advertise? 66 3.2 External fertilization and chemical duets 69 3.3 Scramble competition 69 3.4 Pre-copulatory mate guarding 71 3.5 Contests 72 3.6 Mate choice: overview 73 3.7 Mate choice for good genes, mate quality, and direct benefits 75 3.8 Mate choice for genetic compatibility revealed by chemical cues 81 3.9 Coolidge effects and rejection of past mates: been there, done that 86 3.10 Alternative mating strategies 86 3.11 Post-copulatory sexual selection 87 3.12 Sex pheromones and speciation 90 Summary 103 Further reading 103 4 Coming together and keeping apart: aggregation pheromones and host-marking pheromones 105 4.1 Aggregation pheromones and Allee effects 105 4.2 Host-marking pheromones 110 Summary 112 Further reading 112...

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The reality of invisible chemical signals, pheromones, between members of the same species was recognized long before they could be identified. Charles Darwin proposed that the breeding season sexual smells of male crocodiles, goats and other animals, too, could have evolved by sexual selection of the smelliest males through female choice. But it's not just sex. We now know that pheromones are used by species all across the animal kingdom, in every habitat, and in a wide range of biological contexts, from trail, alarm, and queen pheromones in social insects to the mammary pheromone produced by mother rabbits. Pheromones have provided fascinating examples of signal evolution. In some model organisms, such as moths, Drosophila, Caenorhabditis elegans, and Mus musculus, a complete signaling system can be genetically dissected, from the enzymes producing pheromones, perception by chemosensory receptors, through to the neural circuits processing the signals.