Promiscuous Mating System Research Articles

Dispersion of adult male Peromyscus leucopus in relation to female reproductive status

We studied dispersion of adult male Peromyscus leucopus in relation to the stage of pregnancy of adult females in natural populations monitored with Longworth live traps. Because postpartum mating is common in P. leucopus and days to parturition measures how far a female is from her next mating, we predicted that a female in early pregnancy (many days to parturition) would have fewer adult males in her neighbourhood than a female in late pregnancy (few days to parturition). Number of adult males caught within 30 m of each adult female was recorded and number of days to parturition for each female was obtained by bringing females back to the laboratory and allowing them to give birth. A negative relationship was found between number of adult males in a female's neighbourhood and days to parturition of the female (r = −0.419, p < 0.01), with the latter accounting for 8.8% of the variance in the former. These results support the hypothesis of a promiscuous mating system in P. leucopus.

A promiscuous mating system in the Blue Bird of Paradise Paradisaea rudolphi

We studied nesting behaviour, spatial dispersion of display areas and home range dynamics in the Blue Bird of Paradise Paradisaea rudolphi. We found that (1) females carried out nesting duties alone; (2) males displayed from solitary and dispersed sites; (3) female home ranges overlapped, and (4) males had access to and displayed to numerous females. These data suggest a promiscuous mating system in the Blue Bird of Paradise and resolve earlier controversy over this issue.

A promiscuous mating system in the Blue Bird of Paradise Paradisaea rudolphi

We studied nesting behaviour, spatial dispersion of display areas and home range dynamics in the Blue Bird of Paradise Paradisaea rudolphi. We found that (1) females carried out nesting duties alone; (2) males displayed from solitary and dispersed sites; (3) female home ranges overlapped, and (4) males had access to and displayed to numerous females. These data suggest a promiscuous mating system in the Blue Bird of Paradise and resolve earlier controversy over this issue.

A sexual selection model for hominid evolution

The following paper develops a sexual selection model for the evolution of bipedal locomotion, canine reduction, brain enlargement, language and higher intelligence. The model involves an expansion of Darwin’s ideas about human evolution based on recent elaborations of sexual selection theory. Modern notions about intrasexual competition and female and male choice and their ecological correlates are summarized along with a new model for the role of sexual selection in speciation. Rapid evolution of bipedal locomotion as a male adaptation for nuptial feeding of females is proposed as a model for ape-hominid divergence through sexual selection; canine reduction is attributed to selection for associated epigamic displays. The analogy with male specialization through sexual selection speciation in hamadryas baboons is noted. Subsequent changes in female reproductive physiology are attributed to female competition for increased male parental investment during the time of early Homo andHomo erectus. The origin of higher intellectual and language abilities inHomo sapiens is attributed to male competition through technology and rule production to control resources and females; intellectual abilities involved in social manipulation are attributed to female competition for male parental investment and maintenance of polyandry. The course of hominid evolution is characterized as involving a trend from a promiscuous mating system toward increasing intensity of adaptations for male control of females, and by increasing intensity of female adaptation to maintain male parental investment while circumventing male control.

Pair Formation in Cowbirds: Evidence Found for Screaming but Not Shiny Cowbirds

Sixty Screaming Cowbirds (Molothrus rufoaxillaris) and 150 Shiny Cowbirds (M. bonariensis) were trapped and banded in Buenos Aires Province, Argentina. Analysis of recaptures provided statistical evidence for pair formation in Screaming but not Shiny cowbirds, a result supported by observations of free-living birds. Pairs of Screaming Cowbirds were stable throughout the breeding season. They are probably monogamous. Shiny Cowbirds showed no pattern of association between the sexes. This is consistent with a promiscuous mating system, although this conclusion is tentative. I also present ancillary data on sexual size dimorphism, sex ratio, and related aspects of behavior. Both species are dimorphic in size to a similar extent, although the Screaming Cowbird is slightly larger. Neither species departs from an adult (quaternary) sex ratio of unity. Pairs of Screaming Cowbirds are conspicuous near host nests. Female Shiny Cowbirds are not accompanied by males at nests, but may be accompanied by other females. Shiny Cowbird females were surreptitious near nests. Differences in host selection behavior may have profound effects on other aspects of the species breeding biology.

Sex-related dispersion of breeding deer mice in the Kananaskis Valley, Alberta

Snap trapping of small mammals in the Kananaskis Valley, Alberta, during the breeding seasons of 1982 and 1983 provided data used to analyse sex-related dispersion patterns of adult Peromyscus maniculatus. A dispersion pattern of regular alternation of males and females, within-sex avoidance, and strong between-sex association was found. Within-sex exclusion was better exhibited by females than by males. These data are consistent with what would be expected for a promiscuous mating system. Intraspecific resource partitioning between different sexes may occur through adjustments in spatial relationships.

Spawning behaviour and sexual dimorphism in the North American cyprinid fishNotropis leedsi, the bannerfin shiner

The spawning behaviour and sexual dimorphism of the little known North American cyprinid fish, Notropis leedsi, is described based on observations made in laboratory aquaria. Notropis leedsi is a crevice spawning species, a trait characteristic of members of the subgenus Cyprinella. Males establish breeding territories through ‘mock battles’ and defend them by chasing away intruding males or, at times, through threat displays or ‘mock battles’. Although wild-caught males are significantly larger than females, sexual dimorphism is more pronounced in the colour pattern and fin size, especially the dorsal and anal fins. The modes of spawning behaviour in the genus Notropis are reviewed. The relationship between the promiscuous mating system (polybrachygamy), the crevice spawning mode, and sexual dimorphism in N. leedsi are discussed in relation to current notions regarding sexual selection.

Iridescent polychromatism in a female hummingbird: is it related to feeding strategies?

Iridescent polychromatism in a female hummingbird: is it related to feeding strategies?

Transience of social affiliations among humpback whales (Megaptera novaeangliae) on the Hawaiian wintering grounds

Observations were made from an elevated shore station and from small boats of membership and of changes in membership in pods of humpback whales, Megaptera novaeangliae, assembling in Hawaiian waters during the winter–spring season of 1980. Pod sizes were small, with many singletons, pairs, and triplets, and a few larger sized pods. For pods having a calf present, the modal size was three: the mother, her calf, and an adult "escort" animal. When the calf was absent the modal size was two animals. On the average, 14% of the pods per hour changed membership, either losing or gaining members; for both pods with and without calf, the modal sizes showed the lowest rate of change. The rate of change was seasonally dependent and was at its maximum between mid-February and mid-March, when the relative abundance of whales was also at its maximum. Pods with calf were much more likely to attract new members than to lose members; pods without calf were equally likely to attract or lose members. Twelve cases of photographic resightings of individuals documented changes in affiliations with intervals as short as 1 h. The driving force for the transient nature of pod membership was hypothesized to be the prospecting behavior of mature males searching for sexually mature, receptive females. The overall pattern and duration of social affiliations was consistent with characteristics of polygynous or promiscuous mating systems.

The breeding behaviour of a northern temperate orconectid crayfish, Orconectes rusticus

Observations of breeding activities of male and female crayfish ( Orconectes rusticus) in a natural stream population during the explosive spring breeding period, and supplemental laboratory observations, indicate a promiscuous mating system characterized by intense intermale aggression. Males wandered extensively over the substrate, fought frequently with each other, and attempted to disrupt copulating pairs. Larger males (as distinguished by large chela size) more frequently initiated and won aggressive encounters and interrupted copulating pairs more successfully than smaller males, but were subjected to greater predation. Intense intermale aggression ceased when females sequestered themselves under rocks in the stream or were removed from the laboratory population. Brief resistance by females to approaching males, along with sequestering behaviour, suggests that female choice may also occur.

Spacing and distribution of bowers in Macgregor's Bowerbird (Amblyornis macgregoriae)

Bowerbirds (Ptilonorhynchidae) have been described as exhibiting exploded lek mating patterns. Quantitative documentation and analysis of spatial dispersion, however, is lacking for most species despite its importance to a fundamental understanding of social organization. We studied Macgregor's Bowerbird (Amblyornis macgregoriae) in eastern New Guinea in 1980 and 1981 to quantify spatial distribution and selection of bower sites in relation to ecological and social factors. Forty-two bower sites were located in approximately 750 ha of mid-montane forest. They were linearly and regularly spaced along ridges with a mean inter-bower distance of 169±64 m SD (range 75–348 m). Statistical analysis showed males to be regularly spaced within available habitat. Discriminant analysis of seven habitat variables measured along utilized ridge lines showed that bower sites differed significantly from potentially available sites with respect to slope and width of ridge, closure of canopy, and density of saplings. Placement of bowers with respect to these factors was not correlated with inter-bower distance. Most males maintained only one bower; four (10%) maintained two bowers simultaneously. Males spent an average of 54% of daylight hours within an activity center of 15–20 m radius surrounding the bower and aggressively defended this area against conspecific males. Marauding pressure on bowers was high, and 39% of all observed mating attempts (n=18) were disrupted by neighboring males. Macgregor's Bowerbird exhibits a social system that appears to be intermediate between lek behavior and territoriality, combining the social dynamics and opportunism of the former and the uniform field of display sites and nests of the latter. We hypothesize that dispersion in this species is partly due to males buffering their display space against intruder pressure. We suggest that strict adherence to the dispersion criterion in classifying promiscuous mating systems may be inappropriate.

The Evolution of Monogamy: Hypotheses and Evidence

Recent theoretical insights are helping to clarify how animal mating sys­ tems evolve. An integrated theory is beginning to emerge from the realiza­ tion that males and females have overlapping but nonidentical reproductive interests and that the type of mating system shown by a species results from interactions between the individual interests of each sex. The optimal mat­ ing system for promoting individual reproductive interests often differs for each sex, and when it does, the interests of one sex constrain the reproduc­ tive options open to the other. Thus, mating system theory revolves around two major issues: the factors determining which sex predominates in shap­ ing each mating system, and the factors determining which mating system is optimal for members of the controlling sex. The greatest progress has been made in explaining how polygynous mat­ ing systems evolved, particularly among territorial vertebrates, and more recent work is clarifying the specific environmental conditions involved (4, 46, 145, 146, 161, 227, 244, 246, 247). Promiscuous and polyandrous mating systems are less well understood, but several promising avenues toward a general theory have begun to develop (7 1, 9 1 , 126, 240, 245, 246). In contrast, theoretical work on the evolution of monogamy lags far behind, despite an enormous literature on monogamous animals.

Adaptive significance of postcopulatory guarding of mates and nonmates by male Calopteryx maculata (Odonata)

1. The postcopulatory behavior of the damselfly Calopteryx maculata (De Beauvois) (Odonata: Calopterygidae) was studied in field populations to determine the adaptive significance of guarding of ovipositing females by males. Of particular interest was an explanation for the guarding of ovipositing nonmates by males. A promiscuous mating system and the large variation in mating success (Table 1) among territorial males indicated that sexual selection may have been a significant factor in the evolution of C. maculata postcopulatory behavior. 2. Territorial males defend ovipositing mates by chasing and displaying toward conspecific males attempting takeovers. Guarded mates averaged 12–15 min of undisturbed oviposition while unguarded females averaged only 1–2 min of oviposition prior to disturbance by males. Postcopulatory guarding is advantageous to both sexes because it allows undisturbed oviposition. 3. During mating, 88%–100% of the sperm stored by a female from a previous mating was removed by a male before he transferred his own sperm to her storage organs. Given this potential for sperm displacement, postcopulatory guarding is advantageous to the guarding male since it assures him of fertilizing a substantial number of eggs prior to a subsequent mating by his mate. 4. The duration of guarding (interval between matings) for males was 10–15 min. It did not differ significantly between two populations in on year. Guarding duration did not significantly change with (a) time of day, (b) time devoted to defensive behavior, (c) female arrival rate, and (d) presence of absence of an ovipositing female (Table 2). 5. Males frequently guarded females with which they did not mate. Nonmates were guarded only when the male was simultaneously guarding a mate or had recently mated. These nonmates deposited eggs fertilized by rival males. Their presence did not significantly increase the time and energy expended by guarding males but did attract additional females (Table 3). However, these additional females did not lead to an increase in mating frequency for the guarding male. 6. Three factors appeared to limit the ability of guarding males to exclude or attempt matings with arriving nonmates: (a) a lack of individual recognition, (b) a risk of losing a previous mate while failing to copulate with an arriving female, and (c) a probable physiologic limit to mating frequency. These limitations in male postcopulatory behavior were exploited by females. 7. Some males were not territorial. While appearing less effective at obtaining mates, they devoted no time and energy to defending territories or mates. Because of sperm displacement, their reproductive success depended upon the ability of their mates to exploit the limitations in guarding behavior of territorial males.

Kinship, promiscuity, and communal breeding in the acorn woodpecker

1. Acorn woodpeckers typically live in permanent social groups in which most adults help to incubate and feed the young of a single nest. The selective basis of communal breeding in this species is examined. 2. At the study area in New Mexico, most juveniles did not remain on their natal territories during subsequent breeding seasons. There was also a high rate of turnover among adults within each group. The groups were not composed entirely of extended families, and unrelated adults fed young. Kin selection alone does not appear to be adequate to explain all instances of communal breeding. 3. Immigrants that joined groups before courtship in the spring participated in all phases of reproduction in their new groups. However, immigrants that joined groups after eggs were laid did not incubate or feed the young. This, combined with the high rate of turnover within groups, indicates that hypotheses based upon individual benefits through increased production of young and/or reciprocity are also not sufficient for this species. 4. An examination of the reproductive behavior within groups suggests that the mating system may be promiscuous. It was not possible to identify which individuals were the parents of the young, and all group members normally participated in every phase of reproduction. A promiscuous mating system means that each group member could make a genetic contribution to the young and that all would help to raise the young to protect their genetic investment. 5. Larger groups successfully fledged more young than did smaller groups, and promiscuity may be an individual strategy to insure that all individuals remain within the group and participate in reproduction.

Adaptive Significance of Sexual Dimorphism in Weasels

Field data on Mustela erminea L. were used to examine the adaptive basis for the sexual dimorphism in weasels. Two hypotheses were considered: one proposed by Brown and Lasiewski, and which regards the dimorphism as a result of intersexual selection favouring different food exploitation by males and females; both sexes possibly exploiting and defending an area in common. An alternative hypothesis is suggested in this paper and considers the dimorphism primarily as an adaptation for different roles of males and females in reproduction; small females being selected for on bioenergetic grounds and large males in connection with competitive mating. Intersexual selection favouring different food exploitation has given further advantage to small females and large males and might have increased the dimorphism. Field data showed no long-lasting pair bonds between males and females; movements and behaviour of males during the breeding season indicated a polygynous or promiscuous mating system with the females alone rearing the young. The two sexes exploited different average size of prey and used different hunting techniques (females hunted more in small rodent tunnels). Food of males and females greatly overlapped in autumn and winter when both sexes exploited small rodent populations in the same habitat. In spring and early summer males partly switched to alternative prey, associated with different habitat selection and extensive movements at mating time. Scarcity of basic food small rodents and increased availability of alternative prey tended to encourage habitat and food segregation. The data support the author's hypothesis.

Models of parent-offspring conflict. II. Promiscuity

The population genetics of Trivers (1974) concept of parent-offspring is examined for species in which the effects of the conflict are felt by future half-sibs, as in promiscuous mating systems in which the male shows no parental care. Whether or not a rare conflictor gene will spread in a non-conflictor population depends on ƒ(m) > (m + 1) (0.5m + 1.5) for a dominant gene, and on ƒ(m) > 1 4 (m + 3) for a recessive gene; f( m) is the fitness gained by a conflictor relative to a non-conflictor offspring [ ƒ(m) >1], and m is the amount of parental investment taken by a conflictor relative to m = 1 for a non-conflictor. The ESS value for conflict ( m o) in promiscuous species with zero male parental care has m o = ƒ(m o ) 4[ dƒ(m o ) dm o ] . However, where the male maintains the same harem for several breeding seasons, or where there is promiscuity but both sexes contribute equally to parental care, conditions for conflict are equivalent to monogamy.

SOCIAL FACILITATION OF MALE SEXUAL BEHAVIOR, INTRASEXUAL COMPETITION, AND SEXUAL SELECTION IN THE GUPPY, POECILIA RETICULATA (PISCES: POECILIIDAE).

Sexual selection, as defined by Darwin (1871), consists of two components-competition among individuals of one sex for the opposite sex and an ultimate choice of mates by the latter. Because females generally invest more in offspring production than do males, intrasexual competition is most intense among males, and females ultimately choose among the competing males (Fisher, 1930; Trivers, 1972). Bateman (1948) demonstrated experimentally that intermale competition exists in laboratory populations of Drosophila. In his experiments, most females found mates, but only a low proportion of males did so. Because of intermale competition, most males were unsuccessful in mate acquisition, while a few mated more than once. Generally, a promiscuous mating system is seen in species in which males invest much less in offspring production than do females. Where males and females are equal in reproductive effort, males cannot afford to be promiscuous, so selection favors monogamy (Trivers, 1972). The live-bearing teleost family Poeciliidae is an example of a group of organisms in which males and females exhibit disparate reproductive investments. Females produce large yolky eggs which are fertilized and retained in the ovarion follicles until the young are self-sufficient. Males, on the other hand, invest nothing but gametes, playing no role in care of their offspring. Thus, it would be advantageous for a male to mate with as many females as possible, but for a female to be selective

Social Interactions in Flocks of Courting Wilson's Phalaropes (Phalaropus tricolor)

A remarkable diversity of mating systems and related social behavior patterns is found in the sandpiper family Scolopacidae (including the Phalaropodinae, after Jehl, 1968). Mating systems range from territorial monogamy in the Willet (Cataptrophorus semipalmatus) (Vogt 1938), possible polygyny in the Pectoral Sandpiper (Calidris melanotos) (Pitelka 1959), polyandry in the Northern Phalarope (Phalaropus lobatus) (Raner 1972; Hilden and Vuolanto 1972) to lek promiscuity in the Ruff (Philomachus pugnax) (Hogan-Warburg 1966). In such species as the Pectoral Sandpiper (Pitelka 1959) and the Whiterumped Sandpiper (Calidris fuscicollis) (Parmelee et al. 1968), males play the active role in courtship and only females incubate, whereas the reverse is true in the phalaropes (Tinbergen 1935; H6hn 1967; Bengtson 1968). Between these extremes, other species exhibit varying degrees of role-sharing by the sexes. The strategy of pair formation in a given species probably represents a series of adaptations to a set of social and environmental conditions. Holmes and Pitelka (1966) have presented an ecological classification of social systems in calidridine sandpipers based upon the relative conservatism or opportunism in the manner of environmental exploitation. Their classification attempts to explain in particular the adaptiveness of spacing patterns of individuals during pair formation and the resulting monogamous, polygamous, or promiscuous mating system. In this paper the social phases of early pair formation in Wilson's Phalarope (Phalaropus tricolor) are examined in some detail with a view to interpreting the adaptiveness of the social behavior patterns exhibited. No attempt will be made at this stage to explain the reversal of sex roles, for which this species and its congeners are well known (Bent 1927). A later paper will deal with the interactions of the sexes during the subsequent period of avoidance of conspecifics, during which time the pair bond is completed and nesting initiated. This study follows and supplements earlier investigations into the breeding biology of W lson's Phalarope, most notably those of H6hn (1967) and Johns (1969). Names of taxa follow the classification of Jehl (1968).

Home-Range Size and Overlap in Sceloporus undulatus erythrocheilus (Reptilia: Iguanidae)

A population of the rock-inhabiting lizard, Sceloporus undulatus erythrocheilus, was studied over two activity seasons in the eastern Colorado foothills. The convex polygon method was used to determine home range and figures were adjusted to eliminate sample size bias. Ninety-seven lizards (53 8 and 44 9) were captured. On the basis of ten or more observations, resident adults (= 50 mm snout-vent length) had an average home-range size of 826 m2 for 12 males and 363 m2 for 9 females. Male home-range size decreased significantly after the breeding season. The large degree of male home-range overlap (52%) suggests that home range is not equal to territory in this population. A promiscuous mating system is implied from the overlap of male and female home ranges and from behavioral notes.

Density, habitat, and the mating system of the Western Sandpiper (Calidris mauri).

The hypothesis that intense predation, variable food availability, and increased social interactions in high density populations have been important factors promoting the evolution of polygynous and promiscuous mating systems in certain Calidridine sandpipers (Holmes and Pitelka, 1966) is examined in breeding populations of the Western Sandpiper (Calidris mauri) in subarctic Alaska.Western Sandpipers breed in a habitat consisting of a complex mosaic of wet low-lying marshes and relatively well-drained, heath-covered tundra. They defend small territories and nest on the latter, while some feeding also occurs there. Most foods however are obtained off territory in the wet marshes and along the shores of lakes, rivers and sloughs.Densities in the nesting areas ranged from 132-196 pairs/40 ha at the base of a low range of hills to 200-300/40 ha on hummocks surrounded completely by marsh. These densities, the highest reported for a Calidridine sandpiper, are relatively constant from year to year.The mating system of the Western Sandpiper is monogamous, both sexes incubate and care for young. Correlated with a strong single pair-bond and stable populations is a strong tendency to return to the same site. Of sandpipers marked, an average of 57.6% of males and 48.8% of females returned in succeeding years, frequently to the same territory or its immediate vicinity. Of the pairs returning to the study area in subsequent years, 61.5% reunited.The restriction of nesting activities to heath tundra is considered to be a result of the protection it provides for nests. With the separation of nesting and feeding areas and with relatively abundant food sources that are not significantly affected by weather, a large nesting area is not required, allowing high densities of Western Sandpipers to occupy the patches of heath-covered tundra. In this ecological context, the high intensity of social interactions has not resulted in the evolution of a nonmonogamous mating system. Indeed, the increased protection afforded offspring by the presence of both parents is probably the most important selective force promoting the evolution of the monogamous mating pattern in Western Sandpipers.