Publisher Summary This chapter discusses the information contained in the odorous secretions of mammals and provides a classification system based on the behavioral and chemical analyses. This classification divides social odors into two groups: identifier and emotive. Identifier odors are defined as those produced through the regular metabolic processes of the animal, without specific stimulation. The emotive odors are those produced as the result of some transient emotional state or external stimulus. The chapter categorizes nine different types of information contained in mammalian social odors: species, age, sex, colony membership, individuality, social status, reproductive state, maternal state, and stress odors. Social odors are modified by diet and hormone levels and by bacterial action. When the chemicals and bacteria responsible for producing the social odors have been identified, the responses of test animals show large individual differences. Responses to olfactory stimuli depend on hormonal and experiential factors. Theoretical models in the study of population regulation, sexual selection, kinship recognition, altruism, parental care, and territoriality infer that animals recognize particular individuals and specific relationships, and such recognition may depend to some extent on the information contained in olfactory signals.

Mammalian Social Odors: A Critical Review

The odor-guided behaviors selected for presentation in this paper encompass the major areas of animal behavior, and illustrate the important principal that complex relations exist between odor-guided behaviors, hormonal state, and experiential factors. Clearly, experiences with odors at several life stages results in profound influences upon later behaviors, including those related to eating, mating, fighting, and nesting. Interestingly, only brief social encounters are needed in rats to induce such phenomena as ultrasonic calling to conspecific estrous females or their odors, preferences for estrous over non-estrous odors, and the short-term modification of feeding behaviors. Although the mechanisms behind these intriguing phenomena are poorly understood, it is noteworthy that rats can learn relatively complex concepts on the basis of odors, rivaling even the ability of our own species to learn analogous tasks by visual cues. Despite the fact that close relationships can be demonstrated between odor-guided behaviors and variables such as endocrine state and sexual experience, caution is warranted in assuming that simple causal relations exist between such variables. In normally cycling women, for example, the correlation between olfactory sensitivity and plasma levels of estradiol during the menstrual cycle is relatively high; however, attenuation of the cyclical estradiol fluctuations by oral contraceptives does not eliminate the olfactory fluctuations, suggesting the relation is not causal. In house mice, social experience can override hormonal factors in their odor-guided urine marking and submissive behaviors. Thus, even though androgen titer usually correlates with such measures, a mouse made subordinant in a social encounter will not exhibit scent marking even when its circulating testosterone is maintained at a high level by a silastic implant. Further reason for caution comes from studies that suggest olfactory input influences the endocrine systems of sexually experienced and sexually inexperienced animals in different ways. For example, in sexually experienced male rats, anosmia decreases testosterone and estradiol levels and increases corticosterone levels, whereas in sexually inexperienced ones it has no significant influence on the levels of these steroids. Taken together, such observations suggest that the causal bases of a number of the odor-guided behaviors described in this paper are complex.(ABSTRACT TRUNCATED AT 400 WORDS)

Odor-guided behavior in mammals.

1 The olfactory system of vertebrates.- 1.1 Anatomy.- 1.2 Odorant characteristics.- 1.3 Function of the external nares and related structures.- 1.4 Evolutionary trends.- 1.5 Summary.- 2 Sources and chemistry of vertebrate scent.- 2.1 The sites of odour production.- 2.2 Chemical composition of odorants.- 2.3 Threshold levels of perception.- 3 Detection of food.- 3.1 Responses of young to food odours.- 3.2 The detection of plant food by odorous cues.- 3.3 The detection of animal food by odorous cues.- 3.4 Scavengers.- 3.5 Quasi-parasites.- 3.6 Summary.- 4 Reproductive processes.- 4.1 Sex attraction and recognition the advertisement of sexual status.- 4.2 Detection and induction of oestrus, ovulation and lordosis.- 4.3 Courtship, mating and related behaviours.- 4.4 Pregnancy.- 4.5 Parental behaviour imprinting.- 4.6 Growth physical and psychosexual development.- 4.7 Summary and conclusions.- 5 Odour discrimination and species isolation.- 5.1 Individual odour.- 5.2 Family, population and racial odours.- 5.3 Species odours and sexual isolation.- 5.4 Summary and conclusions.- 6 Dispersion and social integration.- 6.1 Intraspecific aggression.- 6.2 The social hierarchy.- 6.3 Territoriality.- 6.4 Correlation between aggression-motivated behaviour and scent deposition.- 6.5 Summary and conclusions.- 7 Alarm and defence.- 7.1 Detection of the predator.- 7.2 Transmission of alarm or warning signals.- 7.3 Active defence.- 7.4 Protection from intraspecific attack.- 7.5 Summary.- 8 Olfactory navigation and orientation.- 8.1 Olfactory navigation.- 8.2 Homing orientation.- 8.3 Summary.- 9 Applications of researches into olfactory biology.- 9.1 Pest repellents and attractants.- 9.2 Animal husbandry.- 9.3 Miscellaneous applications.- References.- Taxonomie index.

Carol Sue Carter

Papers

Olfactory imprinting and age variables in the guinea-pig, Cavia porcellus.

Effects of olfactory experience on the behaviour of the guinea-pig (Cavia porcellus).