scholarly journals Do Local Sex Ratios Approximate Subjective Partner Markets?

Human Nature ◽  
2021 ◽  
Author(s):  
Andreas Filser ◽  
Richard Preetz
Keyword(s):  
Sex Ratio ◽  
Sex Ratios ◽  
Population Data ◽  
Future Research ◽  
Relationship Formation ◽  
Logistic Regression Models ◽  
Fine Grained ◽  
Adult Sex Ratio ◽  
And Behavior ◽  
Partner Market

AbstractSex ratios have widely been recognized as an important link between demographic contexts and behavior because changes in the ratio shift sex-specific bargaining power in the partner market. Implicitly, the literature considers individual partner market experiences to be a function of local sex ratios. However, empirical evidence on the correspondence between subjective partner availability and local sex ratios is lacking so far. In this paper, we analyzed how closely a set of different local sex ratio measures correlates with subjective partner market experiences. Linking a longitudinal German survey to population data for different entities (states, counties, municipalities), we used multilevel logistic regression models to explore associations between singles’ subjective partner market experiences and various operationalizations of local sex ratios. Results suggest that local sex ratios correlated only weakly with subjective partner market experiences. Adult sex ratios based on broad age brackets, including those for lower-level entities, did not significantly predict whether individuals predominantly met individuals of their own sex. More fine-grained, age-specific sex ratios prove to be better predictors of subjective partner market experiences, in particular when age hypergamy patterns were incorporated. Nevertheless, the respective associations were only significant for selected measures. In a complementary analysis, we illustrate the validity of the subjective indicator as a predictor of relationship formation. In sum, our results suggest that subjective partner availability is not adequately represented by the broad adult sex ratio measures that are frequently used in the literature. Future research should be careful not to equate local sex ratios and conscious partner market experiences.

scholarly journals Do local sex ratios approximate subjective partner markets? Evidence from the German Family Panel

2019 ◽  
Author(s):  
Andreas Filser ◽  
Richard Preetz
Keyword(s):  
Sex Ratio ◽  
Scientific Reasoning ◽  
Sex Ratios ◽  
Social Consequences ◽  
Event History ◽  
Future Research ◽  
Multilevel Regression ◽  
Relationship Formation ◽  
Partner Market ◽  
Market Indicator

A growing body of evidence suggests that imbalanced local sex ratios are correlated with social consequences, including the pattern and timing of union formation, fertility and relationship stability. Scholars have argued that these findings can be understood as a result of imbalances in the bargaining power the respective sex holds in male- or female-skewed regions, but they remain vague on the underlying mechanisms. Specifically, the literature implicitly considers individual partner market experiences to be a function of local sex ratios. However, empirical evidence on the correspondence between subjective partner availability and local sex ratios remains scarce. This study addresses this gap by linking individual-level German longitudinal survey data (pairfam) with local sex ratios from population data for different entities (states, counties, and municipalities). Using multilevel regression models, this paper analyses the correlations between a subjective partner market indicator and a variety of local sex ratio measures. Moreover, an event history analysis explored how either indicator relates transitions into relationships. Results revealed that none of the local sex ratio measures, including those for narrow age ranges and/or lower level administrative entities, significantly predicted whether individuals predominantly met individuals of their own sex. Event history models yielded significant correlations between this subjective partner market indicator and relationship formation for both genders, substantiating the validity of the subjective indicator. For local sex ratios, results revealed an additional association between local sex ratios and female relationship formation when the sex ratios were adjusted for age hypergamy. Male relationship formation was uncorrelated with any local sex ratio. Both evolutionary and social scientific reasoning on the consequences of sex ratio imbalances rest on assumptions of subjective partner availability that may not be adequately represented by local sex ratios. Future research should be careful not to equate local sex ratios and conscious partner market experiences.

scholarly journals Recruitment sex ratios in gray-tailed voles (Microtus canicaudus) in response to density, sex ratio, and season

2003 ◽  
Vol 81 (8) ◽  
pp. 1306-1311 ◽  
Author(s):  
Monica L Bond ◽  
Jerry O Wolff ◽  
Sven Krackow
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Resource Competition ◽  
Sex Ratios ◽  
Female Offspring ◽  
High Population ◽  
Reproductive Value ◽  
High Population Density ◽  
Adult Sex Ratio ◽  
Sex Ratio Adjustment

We tested predictions associated with three widely used hypotheses for facultative sex-ratio adjustment of vertebrates using eight enclosed populations of gray-tailed voles, Microtus canicaudus. These were (i) the population sex ratio hypothesis, which predicts that recruitment sex ratios should oppose adult sex-ratio skews, (ii) the local resource competition hypothesis, which predicts female-biased recruitment at low adult population density and male-biased recruitment at high population density, and (iii) the first cohort advantage hypothesis, which predicts that recruitment sex ratios should be female biased in the spring and male biased in the autumn. We monitored naturally increasing population densities with approximately equal adult sex ratios through the spring and summer and manipulated adult sex ratios in the autumn and measured subsequent sex ratios of recruits. We did not observe any significant sex-ratio adjustment in response to adult sex ratio or high population density; we did detect an influence of time within the breeding season, with more female offspring observed in the spring and more male offspring observed in the autumn. Significant seasonal increases in recruitment sex ratios indicate the capacity of female gray-tailed voles to manipulate their offspring sex ratios and suggest seasonal variation in the relative reproductive value of male and female offspring to be a regular phenomenon.

scholarly journals Phenotypic and environmental predictors of reproductive success in painted turtles

2020 ◽  
Author(s):  
Jessica M. Judson ◽  
Luke A. Hoekstra ◽  
Kaitlyn G. Holden ◽  
Fredric J. Janzen
Keyword(s):  
Body Size ◽  
Reproductive Success ◽  
Mate Choice ◽  
Sex Ratio ◽  
Sex Ratios ◽  
Female Mate Choice ◽  
Painted Turtles ◽  
Weak Evidence ◽  
Adult Sex Ratio ◽  
Siring Success

ABSTRACTSexual selection is often assumed to elicit sexually dimorphic traits. However, most work on this assumption in tetrapod vertebrates has focused on birds. In this field experiment, we assessed relationships between both sexually dimorphic (body size, claw length) and non-dimorphic traits (forelimb stripe color, baseline corticosterone concentrations) and reproductive success in adult painted turtles to explicate the roles of these phenotypes in mate choice and the evolution of sexual dimorphism. We also modified adult sex ratios in experimental ponds to elucidate the role of biased sex ratios on reproductive success, which is a timely test of the potential threat of biased sex ratios on population persistence in a species with temperature-dependent sex determination. We found no strong influence of male phenotypes on male siring success, but female body size and baseline corticosterone concentrations predicted female clutch sizes. We find weak evidence that adult sex ratio influences male siring success, with a male-biased sex ratio producing lower male siring success than a female-biased sex ratio. This study offers evidence that female mate choice may not be an important selective force on male phenotypes, but that instead selection occurs on female phenotypes, particularly body size and corticosterone concentrations. Further, biased adult sex ratios can influence reproductive success of both sexes. Finally, the use of Kompetitive Allele Specific PCR (KASP) was highly successful in parentage analysis, which adds reptiles to the growing list of taxa successfully genotyped with this new technology.Lay SummaryFemale painted turtles aren’t choosy about traits of their mates. In a field experiment, we find that male traits do not predict male fitness, but key female traits (body size and stress levels) do predict female reproductive success. Further, we find weak evidence that adult sex ratio influences individual fitness in this species with environmental sex determination. Ultimately, we reject the long-assumed importance of female mate choice in this freshwater turtle.

The Behavioral Ecology of Sex Tourism: The Consequences of Skewed Sex Ratios

2020 ◽  
pp. 004728752094610
Author(s):  
Florian Kock
Keyword(s):  
Sex Ratio ◽  
Behavioral Ecology ◽  
Sex Ratios ◽  
Reproductive Age ◽  
Operational Sex Ratio ◽  
Future Research ◽  
Sex Tourism ◽  
Same Sex ◽  
Biological Perspective ◽  
Attitudes Toward Sex

The operational sex ratio (i.e., the ratio of reproductive-age females to males in a population) shapes both animal and human behavior in important ways. Drawing on research in evolution and ecology, the author proposes that a local male-skewed sex ratio (i.e., a surplus of males) influences local men’s attitudes toward sex tourism. Analyzing historical field (study 1) and experimental data (study 2), the author demonstrates that male-skewed sex ratios increase men’s sex tourism rationalization and intent, while women’s predispositions are not sensitive to sex ratios. Sex tourism is explained as a subconscious ecological plasticity in response to perceived increased intensities of same-sex competition for mates, signaled by male-skewed sex ratios. The findings demonstrate a link between mating ecologies and sex tourism, with the latter serving as a compensatory behavior of same-sex mating competition. This research contributes a novel, biological perspective on sex tourism with implications for future research and practice.

Sex ratio variation in gastrointestinal nematodes of Svalbard reindeer; density dependence and implications for estimates of species composition

Parasitology ◽  
2004 ◽  
Vol 130 (1) ◽  
pp. 99-107 ◽  
Author(s):  
A. STIEN ◽  
M. DALLIMER ◽  
R. J. IRVINE ◽  
O. HALVORSEN ◽  
R. LANGVATN ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Species Composition ◽  
Density Dependence ◽  
Sex Ratios ◽  
Gastrointestinal Nematodes ◽  
Late Winter ◽  
Adult Males ◽  
Svalbard Reindeer ◽  
Ratio Variation ◽  
Adult Sex Ratio

Estimates of the intensity and abundance of species provide essential data for ecological, evolutionary and epidemiological studies of gastrointestinal nematode communities. These estimates are typically derived from the species composition of adult males when only males have readily scorable species-specific morphological traits. Such estimation assumes that all species in the community have the same adult sex ratio. We evaluated this assumption for the trichostrongyle nematodes Ostertagia gruehneri and Marshallagia marshalli in infracommunities in Svalbard reindeer by identifying to species adult females using a polymerase chain reaction assay. The proportion of males was found to be slightly higher in O. gruehneri than in M. marshalli. Evidence for seasonal variation and density dependence in the adult sex ratio was only found for O. gruehneri. Possible demographic mechanisms for such sex ratio variation are discussed, and stochastic models that generate density-dependent sex ratios proposed. Sex ratio variation caused substantial bias in some male-based estimates of intensity of infection, while substantial and consistent bias in estimates of abundances was only evident in late winter samples. Our results suggest that estimating sex ratios can be particularly important in individual host level studies of nematode species of low abundance.

scholarly journals Estimating adult sex ratios in nature

2017 ◽  
Vol 372 (1729) ◽  
pp. 20160313 ◽  
Author(s):  
Sergio Ancona ◽  
Francisco V. Dénes ◽  
Oliver Krüger ◽  
Tamás Székely ◽  
Steven R. Beissinger
Keyword(s):  
Sex Differences ◽  
Sex Ratio ◽  
Evolutionary Biology ◽  
Adult Population ◽  
Sex Ratios ◽  
Estimation Methods ◽  
Spatial And Temporal Variation ◽  
Animal Populations ◽  
Adult Sex Ratio ◽  
Males And Females

Adult sex ratio (ASR, the proportion of males in the adult population) is a central concept in population and evolutionary biology, and is also emerging as a major factor influencing mate choice, pair bonding and parental cooperation in both human and non-human societies. However, estimating ASR is fraught with difficulties stemming from the effects of spatial and temporal variation in the numbers of males and females, and detection/capture probabilities that differ between the sexes. Here, we critically evaluate methods for estimating ASR in wild animal populations, reviewing how recent statistical advances can be applied to handle some of these challenges. We review methods that directly account for detection differences between the sexes using counts of unmarked individuals (observed, trapped or killed) and counts of marked individuals using mark–recapture models. We review a third class of methods that do not directly sample the number of males and females, but instead estimate the sex ratio indirectly using relationships that emerge from demographic measures, such as survival, age structure, reproduction and assumed dynamics. We recommend that detection-based methods be used for estimating ASR in most situations, and point out that studies are needed that compare different ASR estimation methods and control for sex differences in dispersal. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies’.

scholarly journals Adolescent school injuries and classroom sex compositions in German secondary schools

2021 ◽  
Author(s):  
Andreas Filser ◽  
Sven Stadtmüller ◽  
Robert Lipp ◽  
Richard Preetz
Keyword(s):  
Sex Ratio ◽  
Secondary Schools ◽  
Risk Taking ◽  
Regression Models ◽  
Sex Ratios ◽  
Peer Groups ◽  
Positive Association ◽  
Logistic Regression Models ◽  
Adolescent Students ◽  
Males And Females

School injuries are an important adolescent health problem. Previous research suggests that relevant risk behaviors for school injuries, risk-taking and aggression, are highly susceptible to peer effects. Specifically, evidence suggests that the ratio of males and females in peer groups (sex ratio) affects individuals’ propensity for aggression and risk-taking. However, research so far has ignored potential associations of classroom sex ratios with adolescent school injury risks. In this paper, we investigate the association of classroom sex compositions with adolescent school injuries in a longitudinal survey dataset containing 13,131 observations from 9,204 adolescent students (ages 13-16) from secondary schools in Germany. The data also allow us to identify injuries that were due to aggressive behavior and analyze these injuries in detail. Results from multilevel logistic regression models reveal that adolescent students’ risk for school injuries is significantly and positively associated with male-skewed classroom sex ratios. Moreover, we find an even stronger positive association between male-dominated classrooms and aggression-injury risks. Finally, we find that both boys’ and girls’ injury risks equally increase with a higher proportion of males in their classroom. We discuss the implications of our findings with regard to the sex ratio literature and potential interventions.

scholarly journals Adolescent school injuries and classroom sex compositions in German secondary schools

2022 ◽  
Vol 22 (1) ◽  
Author(s):  
Andreas Filser ◽  
Sven Stadtmüller ◽  
Robert Lipp ◽  
Richard Preetz
Keyword(s):  
Sex Ratio ◽  
Secondary Schools ◽  
Risk Taking ◽  
Sex Ratios ◽  
Peer Groups ◽  
Positive Association ◽  
Male Students ◽  
Logistic Regression Models ◽  
Adolescent Students ◽  
Intervention Planning

Abstract Background School injuries are an important adolescent health problem. Previous research suggests that relevant risk behaviors for school injuries, risk-taking and aggression, are highly susceptible to peer effects. Specifically, evidence suggests that the ratio of men and women in peer groups (sex ratio) affects individuals’ propensity for aggression and risk-taking. However, potential associations of classroom sex ratios with adolescent school injury risks have not been studied so far. The purpose of this paper is to investigate the association of classroom sex compositions with adolescent school injuries. Methods We investigate the association of classroom sex ratios with school injuries in a longitudinal survey dataset containing 13,131 observations from 9,204 adolescent students (ages 13-16) from secondary schools in Germany. The data also allow us to identify injuries due to aggressive behavior and analyze these injuries in detail. We use multilevel logistic regression models to analyze risks of both overall and aggression-related school injuries. Results Adolescent students’ risk for school injuries is significantly and positively associated with male-skewed classroom sex ratios (OR = 1.012, p=0.012). Specifically, the risk of sustaining a school injury increases by 33.5 percent when moving from the 10th to the 90th classroom sex ratio percentile. Moreover, we find an even stronger positive association between male-dominated classrooms and aggression-related injury risks (OR = 1.022, p=0.010). Compared to classroom sex ratios at the 10th percentile, the risk of an aggression-related injury is 78 percent higher in classrooms with a sex ratio at the 90th percentile. Finally, we find that both boys’ and girls’ injury risks equally increase with a higher proportion of male students in their classroom. Conclusions Our findings indicate that sex composition of classrooms is an important contextual factor for adolescent school injuries, in particular school injuries resulting from aggression. These findings illustrate the need to integrate a contextual perspective on school injuries among adolescent students both into research and into intervention planning.

Male-biased adult sex ratios in a red squirrel population

1987 ◽  
Vol 65 (5) ◽  
pp. 1284-1286 ◽  
Author(s):  
T. Andrew Hurly
Keyword(s):  
Sex Ratio ◽  
Habitat Use ◽  
Sex Ratios ◽  
Sexual Differences ◽  
Differential Mortality ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Male Mortality ◽  
Adult Sex Ratio ◽  
Sampling Biases

A 3-year study of a red squirrel population revealed that the adult sex ratio was biased towards males. There is no evidence that the skewed sex ratio was prejudiced by sampling biases due to sexual differences in mobility, observability, trappability, or habitat use. The tertiary juvenile sex ratio was even and therefore not the cause of the biased adult sex ratio. The data suggest that the skewed sex ratio may be the result of differential mortality. This is consistent with other reports of higher female than male mortality in red squirrels.

scholarly journals Adult sex ratios and reproductive strategies: a critical re-examination of sex differences in human and animal societies

2017 ◽  
Vol 372 (1729) ◽  
pp. 20160309 ◽  
Author(s):  
Ryan Schacht ◽  
Karen L. Kramer ◽  
Tamás Székely ◽  
Peter M. Kappeler
Keyword(s):  
Sex Differences ◽  
Sex Ratios ◽  
Relative Proportion ◽  
Relative Number ◽  
Future Research ◽  
Theme Issue ◽  
Wide Audience ◽  
Adult Sex Ratio ◽  
Introductory Paper ◽  
Animal Societies

It is increasingly recognized that the relative proportion of potential mates to competitors in a population impacts a range of sex-specific behaviours and in particular mating and reproduction. However, while the adult sex ratio (ASR) has long been recognized as an important link between demography and behaviour, this relationship remains understudied. Here, we introduce the first inter-disciplinary collection of research on the causes and consequences of variation in the ASR in human and animal societies. This important topic is relevant to a wide audience of both social and biological scientists due to the central role that the relative number of males to females in a population plays for the evolution of, and contemporary variation in, sex roles across groups, species and higher taxa. The articles in this theme issue cover research on ASR across a variety of taxa and topics. They offer critical re-evaluations of theoretical foundations within both evolutionary and non-evolutionary fields, and propose innovative methodological approaches, present new empirical examples of behavioural consequences of ASR variation and reveal that the ASR plays a major role in determining population viability, especially in small populations and species with labile sex determination. This introductory paper puts the contributions of the theme issue into a broader context, identifies general trends across the literature and formulates directions for future research. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.

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