Sandpiers (family Scolopacidae, order Charadriiformes), have many aspects of reproductive biology in common. Most of the eighty-six species are migratory, and breed in the arctic or north temperate zone. Females typically lay clutches of four eggs in ground nests. The young have well-developed down, legs, and visual senses at hatch, and feed themselves on small invertebrates. Parental care involves brooding very small chicks, and protecting by vocal warning calls or by attacking or distracting predators.

In spite of these common features, members of this family exhibit a wide spectrum of mating and parental care systems. Monogamy with some degree of...

How has the environment shaped the moorhen social system? A social system is essentially a description of two main aspects of animal existence: 1) the spacing pattern of the individuals (e.g., whether they form groups) and 2) the form of the mating system (e.g., whether individuals are monogamous or polygamous). These patterns are a consequence of “decisions” taken by individuals, for example, when an individual finds that the benefits of joining a group outweigh the costs. A social system is a description of the sum of the social behaviors of the individuals that compose it (Gosling and Petrie, 1981). It...

Family Canidae is composed of approximately thirty-seven species with mean female body weight ranging from 1.5 kg (Fennecus zerda, fennec fox) to 31.1 kg (Canis lupus, timber wolf) (Clutton-Brock et al., 1976; Gittleman, 1984a). Among canids, the basic mating system is long-term monogamy, a system that is rare among mammals (< 3%; Kleiman, 1977). However, an examination of the social organization in the continuum of small to large canids reveals major trends in adult sex ratio, dispersal, mating systems, and neonate rearing systems (Table 4.1). Small canids (< 6.0 kg) tend to have an adult sex ratio skewed toward females,...

Florida scrub jays (Aphelocoma c. coerulescens) breed as monogamous pairs. These pairs mate for life, and dwell in large all-purpose territories which they defend the year round. As breeders, males and females experience equal survivorship, and the same appears to be true for fledglings during the first twelve months of life. As young yearlings all jays, male and female, remain in their natal territory where they help the resident breeders (usually their parents) raise a new brood of offspring. Despite these fundamental similarities between the sexes in survivorship and mating strategy, substantial differences exist between the sexes in dispersal and...

All hornbills for which there is information mate monogamously (Kemp, 1979), but in some species a dominant, breeding pair lives in territorial, “cooperatively breeding” groups with auxiliary, nonbreeding helpers-at-the nest (as defined by Emlen and Vehrencamp, 1983; Emlen, 1984). A rich body of long-term empirical studies have been instrumental in integrating behavioral, demographic, and ecological factors into a theory of cooperative breeding in birds (J. L. Brown, 1978; Emlen, 1982a, 1982b; Emlen and Vehrencamp, 1983; Gaston, 1978; Koenig and Pitelka, 1981; Ricklefs, 1975). Exemplary studies include those of J. L. Brown (1974) on Mexican jays, Woolfenden and Fitzpatrick (1978; Chapter...

The mongooses comprise a large and relatively unstudied carnivore group showing considerable diversity in ecology and social organization. They occur in habitats from rain forest to semi-desert, may be either diurnal or nocturnal, and feed on a variety of prey from insects to rats and birds. Most of the thirty-six species of mongooses are solitary, but eight species in four genera travel and den in cohesive groups which usually contain several adult males and females. What ecological factors have been responsible for differences in the social systems of the mongooses and how has sociality evolved in the group? This chapter...

Dabbling ducks (Anatini) pose several intriguing problems for behavioral ecologists. Why do they differ from most birds in that females, rather than males, are philopatric? Why are they basically monogamous, given that males do not incubate and play no part in brood care in most species? Why does pairing occur in winter, often months before breeding begins, and why are new pair bonds usually formed each year? Why do males of certain species defend breeding territories? In the light of current views on sex-biased dispersal (Greenwood, 1980), mating system evolution (Emlen and Oring, 1977), and pair-bond duration (Rowley, 1983), these...

The spatial and temporal distribution of reproductive females and the extent of male parental care needed are increasingly regarded as the primary determinants of avian mating systems (Orians, 1969; Emlen and Oring, 1977; Oring, 1982). Ecological factors that promote clumping of females, such as predation and spatially variable food resources, favor the evolution of polygyny because males have the opportunity to defend more than one female (Emlen and Oring, 1977). Studies of the subfamily Icterinae, which includes New World orioles and blackbirds, have been very important in developing and testing this model (e.g., Orians, 1980). Species in which females nest...

Traditionally, primate social systems have been characterized according to patterns of male residence: that is, as monogamous, uni-male (harem), or multimale (e.g., Crook and Gartlan, 1966; Crook, 1972; Eisenberg et al., 1972; Goss-Custard et al., 1972; Clutton-Brock and Harvey, 1977). However, because of the diversity and complexity of primate social relationships, these classifications are of only limited value in predicting the type of mating system a particular population or species is likely to display.

The mating patterns within any breeding population are determined by the interactions between the reproductive behavior of females and males. Consequently, attempts to understand the causes...

Human social systems have been studied extensively. We probably know more about the particular patterns of human pair-bond formation than about the patterns of any other species. Nevertheless, there have been few attempts to use this knowledge of human behavior to test hypotheses from biological theory.

Other chapters in this volume summarize current knowledge of male and female reproductive strategies in a number of species of birds and mammals. In this chapter we examine data from 849 human societies. Our aim is to test predictions about human mating and marriage systems derived from the same evolutionary principles used in the...

The theme of this chapter is that variation in the mating strategies of male antelopes is a consequence of differing adaptations to maximize encounters with sexually receptive females. The argument thus depends to a large extent on female behavior and, while this has not been studied in detail, it is possible to make generalizations which are sufficient for the present aims. The first is that almost all parental care is by females; males that accompany females might contribute to the survival of their own offspring by detecting or repelling predators but, in general, male parental investment is limited to the...

For a family containing only seven species, the Equidae show a remarkable diversity of social systems. Horses (Equus przewalskiiandE. caballus), plains zebra (E. burchelli), and mountain zebra (E. zebra) typically live in closed membership harem groups consisting of adult females, a single adult male, and their young (Klingel, 1974). In contrast, Grevy’s zebra (E. grevyi) and the asses (E. africanusandE. hemionus) typically exhibit social systems in which female bonds are more ephemeral. Temporary aggregations of one or both sexes are common, but most adult males live alone in large territories (Klingel, 1974). Even though in both...

Much of the focus on the nature of mating systems has centered on determining the conditions under which polygyny evolves. One model, the polygyny threshold, states that a female should choose to mate with an already mated male when she can expect greater reproductive success than if she mated with a remaining unmated male (Verner and Willson, 1966; Orians, 1969). In this model, both males and females benefit. The underlying assumption in the study of mating systems is that individuals attempt to maximize fitness. An analysis of the mating system of the yellow-bellied marmot revealed that the fitness of individual...

During the 1960s, one of the main preoccupations of field workers was to relate the range of social systems they observed in nature to underlying environmental determinants. This endeavor, known generally as socioecology, was particularly associated with the name of John Crook (see Crook, 1970; Crook and Gartlan, 1966). Subsequently, the rise of sociobiology in the later 1970s altered the emphasis from group-level phenomena to the behavior of the individual. There was a consequent shift in the problems that interested field workers, with species-based studies giving way to problem-based studies in which the identity of the species was often incidental....

For a family containing only four species, the social systems of the great apes are strikingly diverse. Orangutans (Pongo pygmaeus) are essentially solitary. Gorillas (Gorilla gorilla) form stable bisexual groups with rarely more than two males or six females. Chimpanzees (Pan troglodytes) and bonobos (or pygmy chimpanzees) (P. paniscus) live in closed social networks (communities) with as many as one hundred or more individuals. Within communities the mating systems and association patterns of the two chimpanzee species differ substantially.

These social variations present an attractive problem because the ecology of the four species is similar in many ways. All are...

Leks, male assemblies that females visit for mating, are a spectacular, but uncommon promiscuous mating system that occurs in a diverse set of vertebrate and invertebrate taxa (Bradbury, 1981; Oring, 1982; Thornhill and Alcock, 1983). Lek systems are commonly defined by four criteria: absence of paternal care, clusters of displaying males, location of mating aggregations away from resources required by females, and apparent freedom of females to choose mates. Additional, but not defining, characteristics of most vertebrate Iek species are highly skewed male mating success and, presumably as a result, pronounced sexual dimorphism.

These features are classically illustrated by sage...

The eastern grey kangarooMacropus giganteusis one of the largest of the Macropodidae, a family of Australasian marsupial herbivores whose species occupy niches equivalent to those of the medium and small ungulates on other continents. Eastern grey kangaroos are among the most social macropodid species, yet their groups are usually small, despite their preference for mesic, lightly wooded, or savanna habitats. To a biologist familiar with the social organization of ungulates of similar size, organization of kangaroo society is remarkably obscure. Overtly defined and defended territories, leks, temporary or permanent monopolization of a group of females by one adult...

Perhaps no mammals are as conspicuously solitary as members of the Felidae, yet the felids include one of the most remarkably social of all mammalian species: the African lion. Because almost all cat species are strictly carnivorous and females are solitary in all species except lions, comparison of the ecology of female lions with that of other felids should reveal the conditions that have resulted in lion sociality.¹ Until now, most reviews of felid sociality have ascribed group living in lions to the “advantages” of cooperative hunting of large prey (e.g., Schaller, 1972; Kruuk, 1972; Bertram, 1978, 1979; Gittleman, 1984;...

One aim of this book is to examine the extent to which social evolution in different taxonomic groups can be understood through a series of common principles. At the most general level the same fundamental rules presumably relate ecology and social organization in all animals: social behavior evolves as an adaptation to maximize fitness, given a particular set of ecological pressures. However, the precise way in which ecological pressures generate social organization in different taxa is not yet firmly known. Furthermore, the problem of understanding socio-ecological principles has in some respects been made more difficult than it was twenty years...