Male Behavior Research Articles

Does the potential strength of sexual selection differ between mating systems with and without defensive behaviours? A meta-analysis.

The Darwin-Bateman paradigm predicts that females enhance their fitness by being choosy and mating with high-quality males, while males should compete to mate with as many females as possible. In many species, males enhance their fitness by defending females and/or resources used by females. That is, males directly defend access to mating opportunities. However, paternity analyses have repeatedly shown that females in most species mate polyandrously, which contradicts traditional expectations that male defensive behaviours lead to monandry. Here, in an extensive meta-analysis, encompassing 109 species and 1026 effect sizes from across the animal kingdom, we tested if the occurrence of defensive behaviours modulates sexual selection on females and males. If so, we can illuminate the extent to which males really succeed in defending access to mating and fertilisation opportunities. We used four different indices of the opportunity for sexual selection that comprise pre-mating and/or post-mating episodes of selection. We found, for both sexes, that the occurrence of defensive behaviours does not modulate the potential strength of sexual selection. This implies that male defensive behaviours do not predict the true intensity of sexual selection. While the most extreme levels of sexual selection on males are in species with male defensive behaviours, which indicates that males do sometimes succeed in restricting females' re-mating ability (e.g. elephant seals, Mirounga leonina), estimates of the opportunity for sexual selection vary greatly across species, regardless of whether or not defensive behaviours occur. Indeed, widespread polyandry shows that females are usually not restricted by male defensive behaviours. In addition, our results indicate that post-mating episodes of selection, such as cryptic female choice and sperm competition, might be important factors modulating the opportunity for sexual selection. We discuss: (i) why male defensive behaviours fail to lower the opportunity for sexual selection among females or fail to elevate it for males; (ii) how post-mating events might influence sexual selection; and (iii) the role of females as active participants in sexual selection. We also highlight that inadequate data reporting in the literature prevented us from extracting effect sizes from many studies that had presumably collected the relevant data.

Biological aging of two innate behaviors of Drosophila melanogaster: Escape climbing versus courtship learning and memory.

Motor and cognitive aging can severely affect life quality of elderly people and burden health care systems. In search for diagnostic behavioral biomarkers, it has been suggested that walking speed can predict forms of cognitive decline, but in humans, it remains challenging to separate the effects of biological aging and lifestyle. We examined a possible association of motor and cognitive decline in Drosophila, a genetic model organism of healthy aging. Long term courtship memory is present in young male flies but absent already during mid life (4-8 weeks). By contrast, courtship learning index and short term memory (STM) are surprisingly robust and remain stable through mid (4-8 weeks) and healthy late life (>8 weeks), until courtship performance collapses suddenly at ~4.5 days prior to death. By contrast, climbing speed declines gradually during late life (>8 weeks). The collapse of courtship performance and short term memory close to the end of life occur later and progress with a different time course than the gradual late life decline in climbing speed. Thus, during healthy aging in male Drosophila, climbing and courtship motor behaviors decline differentially. Moreover, cognitive and motor performances decline at different time courses. Differential behavioral decline during aging may indicate different underlying causes, or alternatively, a common cause but different thresholds for defects in different behaviors.

Jihad and Heroic Hypermasculinity – Recruitment Strategies, Battlefield Experiences, and Returning Home

There is a gap in knowledge when it comes to jihadism and how it is associated with notions of masculinity. Especially empirical studies on masculinity that are based on interviews with active or former jihadists are lacking. This study seeks to analyze the role that notions of masculinity have played in different phases of jihadiship among Swedish jihadist foreign fighters, from recruitment to traveling to the conflict zone, and then eventually returning to Sweden. With a focus on heroic jihadist hypermasculinity, which is a form of hegemonic masculinity that exaggerates male stereotypical behavior such as violence and aggression, the study identifies five themes: Recruitment strategies and masculinity; from masculine failure to protecting sisters in faith; jihad and street culture; the warrior ideal; jihad, patriarchy, and brotherhood; and returning home and preventing re-emasculation. The empirical material is based on interviews with six Swedish jihadists and a former jihadist recruiter.

Development and validation of the relational behavior interactions scale for couples

In this research, we developed and validated a measure of couple-based reported behavior interactions (RBI). Specifically, Study 1 was designed to describe the development of the scale and to examine its reliability; Study 2 (N = 222), was designed to examine factors that could differentiate men and women. Additionally, we tested if women's behaviors could predict their partner's behavior. Results from the exploratory factor analysis (EFA) revealed a three-factor structure for couples' RBI which were labelled: Social Companionship and Affective Behavior Interactions (SAI) (Factor 1), Fulfilling Obligations and Duties of the Partner (FOD) (Factor 2) and Openness in the Relationship (OR) (Factor 3). In linear regression analyses, there was a significant difference between men and women in the second factor, which represents behaviors associated with fulfilling the responsibilities of a partner. On the other hand, neither the SAI factor nor the OR factor showed any distinct gender differences. The SPSS PROCESS analysis revealed that women's Social Companionship and Affective Behavior Interactions (Factor 1), and Openness in the Relationship (Factor 3) significantly predicted their male partner's behaviors. The relationship duration significantly moderated the association between women's and men's behaviors for both factors. Results are discussed in light of the need for a broader understanding of romantic behavioral interactions.

Risk-sensitive learning is a winning strategy for leading an urban invasion.

In the unpredictable Anthropocene, a particularly pressing open question is how certain species invade urban environments. Sex-biased dispersal and learning arguably influence movement ecology, but their joint influence remains unexplored empirically, and might vary by space and time. We assayed reinforcement learning in wild-caught, temporarily captive core-, middle-, or edge-range great-tailed grackles-a bird species undergoing urban-tracking rapid range expansion, led by dispersing males. We show, across populations, both sexes initially perform similarly when learning stimulus-reward pairings, but, when reward contingencies reverse, male-versus female-grackles finish 'relearning' faster, making fewer choice-option switches. How do male grackles do this? Bayesian cognitive modelling revealed male grackles' choice behaviour is governed more strongly by the 'weight' of relative differences in recent foraging payoffs-i.e., they show more pronounced risk-sensitive learning. Confirming this mechanism, agent-based forward simulations of reinforcement learning-where we simulate 'birds' based on empirical estimates of our grackles' reinforcement learning-replicate our sex-difference behavioural data. Finally, evolutionary modelling revealed natural selection should favour risk-sensitive learning in hypothesised urban-like environments: stable but stochastic settings. Together, these results imply risk-sensitive learning is a winning strategy for urban-invasion leaders, underscoring the potential for life history and cognition to shape invasion success in human-modified environments.

Differences in help-seeking behaviour between males and females with multiple pelvic floor symptoms: A qualitative study

BackgroundPelvic floor symptoms (PFS) are common and frequently co-occur, but few patients seek help despite negative effects on their quality of life. Moreover, most studies assessing help-seeking behaviour have only focused on a single PFS. AimWe aimed to explore the barriers to and facilitators of help-seeking behaviour in males and females with at least two PFS. Design and SettingThis interview-based study included participants by age and symptoms (number and type) from a larger group taking part in a survey on PFS in the general population. MethodTwo researchers independently encoded and analyzed the semi-structured interviews, which continued to saturation for both the male and female cohorts. ResultsOf the 25 participants (13 male and 12 female), 9 sought help for all PFS, 10 did not seek help for any PFS, and 6 sought help for some PFS. We identified themes in domains related to the patient, healthcare professional, environment, and symptoms. Although most themes applied to both sexes, some had greater sex specificity. ConclusionMales and females have more similarities than differences in help-seeking behaviour. Healthcare providers should know that patients who seek help for one symptom probably have multiple PFS that the patient has not reported.

The melanin pigment gene black mediates body pigmentation and courtship behaviour in the German cockroach Blattella germanica.

Genes involved in melanin production directly impact insect pigmentation and can affect diverse physiology and behaviours. The role these genes have on sex behaviour, however, is unclear. In the present study, the crucial melanin pigment gene black was functionally characterised in an urban pest, the German cockroach, Blattella germanica. RNAi knockdown of B. germanica black (Bgblack) had no effect on survival, but did result in black pigmentation of the thoraxes, abdomens, heads, wings, legs, antennae, and cerci due to cuticular accumulation of melanin. Sex-specific variation in the pigmentation pattern was apparent, with females exhibiting darker coloration on the abdomen and thorax than males. Bgblack knockdown also resulted in wing deformation and negatively impacted the contact sex pheromone-based courtship behaviour of males. This study provides evidence for black function in multiple aspects of B. germanica biology and opens new avenues of exploration for novel pest control strategies.

A variance-partitioning approach for assessing mate choice and which sex controls mating behavior

Abstract Mating behavior arises from interactions between males and females. The precopulatory stage includes various male and female mating behaviors that are potentially influenced (independently or jointly) by each sex, thereby shaping the dynamics of this stage. However, limited attention has been given to determining the relative contributions of males and females to the expression of precopulatory behaviors. Here, we adopted a variance-partitioning approach to assess which sex controls each precopulatory behavior. This approach also enabled us to evaluate the existence of mate choice by assessing whether the expression of precopulatory behavior depends on the identity of the opposite-sex partner. In our study, using the bean bug Riptortus pedestris, we exposed individual males and females to different opposite-sex partners (i.e., mating assays) up to six times. During the mating assay, we measured multiple precopulatory behaviors (e.g., latency to mount, courtship rate, courtship duration, and duration of position change). Variance partitioning showed that the variation in each precopulatory behavior could be attributed solely to either sex but not to both sexes. Hence, the precopulatory stage of R. pedestris comprises a combination of male-controlled and female-controlled behaviors. We also suggested that mate choice was absent in both sexes of R. pedestris in the postmounting and precopulatory stages. Our findings highlight the importance of the variance-partitioning approach in the study of mating behavior, as it facilitates the investigation of whether mate choice occurs at specific mating stages and enhances our understanding of evolutionary dynamics during mating.

Interactive parallel sex pheromone circuits that promote and suppress courtship behaviors in the cockroach.

Many animals use multicomponent sex pheromones for mating, but the specific function and neural processing of each pheromone component remain unclear. The cockroach Periplaneta americana is a model for studying sex pheromone communication, and an adult female emits major and minor sex pheromone components, periplanone-B and -A (PB and PA), respectively. Attraction and courtship behaviors (wing-raising and abdominal extension) are strongly expressed when adult males are exposed to PB but weakly expressed when they are exposed to PA. When major PB is presented together with minor PA, behaviors elicited by PB were impaired, indicating that PA can both promote and suppress courtship behaviors depending on the pheromonal context. In this study, we identified the receptor genes for PA and PB and investigated the effects of knocking down each receptor gene on the activities of PA- and PB-responsive sensory neurons (PA- and PB-SNs), and their postsynaptic interneurons, and as well as effects on courtship behaviors in males. We found that PB strongly and PA weakly activate PB-SNs and their postsynaptic neurons, and activation of the PB-processing pathway is critical for the expression of courtship behaviors. PA also activates PA-SNs and the PA-processing pathway. When PA and PB are simultaneously presented, the PB-processing pathway undergoes inhibitory control by the PA-processing pathway, which weakens the expression of courtship behaviors. Our data indicate that physiological interactions between the PA- and PB-processing pathways positively and negatively mediate the attraction and courtship behaviors elicited by sex pheromones.

Observations of reproductive behaviors in the Critically Endangered bowmouth guitarfish Rhina ancylostoma

Wedgefishes, family Rhinidae, are collectively identified as one of the most threatened groups of chondrichthyan fishes globally by the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species. Within the family Rhinidae, bowmouth guitarfish Rhina ancylostoma have been designated by the IUCN as Critically Endangered since 2018. Bowmouth guitarfish were first introduced to the Association of Zoos and Aquariums (AZA) in 2005 when the Newport Aquarium, Newport, KY, USA, acquired a single female. In 2007, a male bowmouth guitarfish was added into the collection with the goal of establishing an institutional breeding program and to generate foundational knowledge for future breeding programs. This study presents an ethogram of mating behaviors exhibited by a mixed sex group of bowmouth guitarfish using behavioral observations from December 2017 through August 2022. The observed interactions between male and female bowmouth guitarfish led to the identification of 5 male reproductive behaviors: hovering, chasing, wrapping up, flipping/rolling, and copulation. These 5 behaviors were directly linked with successful reproduction, e.g. active breeding and live parturition, in the imperiled species R. ancylostoma. The breeding behavioral knowledge presented within this study provides the first step to a viable breeding program, a critical tool for conserving wild populations.

Microglial sex differences in innate high anxiety and modulatory effects of minocycline

Microglia modulate synaptic refinement in the central nervous system (CNS). We have previously shown that a mouse model with innate high anxiety-related behavior (HAB) displays higher CD68+ microglia density in the key regions of anxiety circuits compared to mice with normal anxiety-related behavior (NAB) in males, and that minocycline treatment attenuated the enhanced anxiety of HAB male. Given that a higher prevalence of anxiety is widely reported in females compared to males, little is known concerning sex differences at the cellular level. Herein, we address this by analyzing microglia heterogeneity and function in the HAB and NAB brains of both sexes. Single-cell RNA sequencing revealed ten distinct microglia clusters varied by their frequency and gene expression profile. We report striking sex differences, especially in the major microglia clusters of HABs, indicating a higher expression of genes associated with phagocytosis and synaptic engulfment in the female compared to the male. On a functional level, we show that female HAB microglia engulfed a greater amount of hippocampal vGLUT1+ excitatory synapses compared to the male. We moreover show that female HAB microglia engulfed more synaptosomes compared to the male HAB in vitro. Due to previously reported effects of minocycline on microglia, we finally administered oral minocycline to HABs of both sexes and showed a significant reduction in the engulfment of synapses by female HAB microglia. In parallel to our microglia-specific findings, we further showed an anxiolytic effect of minocycline on female HABs, which is complementary to our previous findings in the male HABs. Our study, therefore, identifies the altered function of synaptic engulfment by microglia as a potential avenue to target and resolve microglia heterogeneity in mice with innate high anxiety.

The effects of paternal dietary fat versus sugar on offspring body composition and anxiety-related behavior

Increasing evidence suggests that the pre-conception parental environment has long-term consequences for offspring health and disease susceptibility. Though much of the work in this field concentrates on maternal influences, there is growing understanding that fathers also play a significant role in affecting offspring phenotypes. In this study, we investigate effects of altering the proportion of dietary fats and carbohydrates on paternal and offspring body composition and anxiety-related behavior in C57Bl/6-JArc mice. We show that in an isocaloric context, greater dietary fat increased body fat and reduced anxiety-like behavior of studs, whereas increased dietary sucrose had no significant effect. These dietary effects were not reflected in offspring traits, rather, we found sex-specific effects that differed between offspring body composition and behavioral traits. This finding is consistent with past paternal effect studies, where transgenerational effects have been shown to be more prominent in one sex over the other. Here, male offspring of fathers fed high-fat diets were heavier at 10 weeks of age due to increased lean body mass, whereas paternal diet had no significant effect on female offspring body fat or lean mass. In contrast, paternal dietary sugar appeared to have the strongest effects on male offspring behavior, with male offspring of high-sucrose fathers spending less time in the closed arms of the elevated plus maze. Both high-fat and high-sugar paternal diets were found to reduce anxiety-like behavior of female offspring, although this effect was only evident when offspring were fed a control diet. This study provides new understanding of the ways in which diet can shape the behavior of fathers and their offspring and contribute to the development of dietary guidelines to improve obesity and mental health conditions, such as anxiety.

Men working through mobile applications in Brazil: Reflections from occupational health

Work through mobile applications emerged as an alternative for many Brazilian men during the economic crisis and rising unemployment. However, these workers operate informally, without a formal employment relationship, leading to labor precariousness and a lack of workers' rights. Using a theoretical-reflexive, this study analyzes the intersection between occupational health, the platformization of work, and the specific challenges faced by male delivery app workers, especially during the COVID-19 pandemic. Reflective categories are divided into two thematic sections: "Labor insertion through mobile applications in Brazil and the algorithmic work model" and "men, health, and motorcycles: occupational health and male behavior in app-based delivery work." The study examines the expansion of this type of work in the Brazilian socio-economic context, the lack of security and labor protection for these workers, as well as the risks faced, particularly during the pandemic, within a male-centric culture.

Increased gene dosage of RFWD2 causes autistic-like behaviors and aberrant synaptic formation and function in mice

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interactions, communication deficits and repetitive behaviors. A study of autistic human subjects has identified RFWD2 as a susceptibility gene for autism, and autistic patients have 3 copies of the RFWD2 gene. The role of RFWD2 as an E3 ligase in neuronal functions, and its contribution to the pathophysiology of ASD, remain unknown. We generated RFWD2 knockin mice to model the human autistic condition of high gene dosage of RFWD2. We found that heterozygous knockin (Rfwd2+/−) male mice exhibited the core symptoms of autism. Rfwd2+/− male mice showed deficits in social interaction and communication, increased repetitive and anxiety-like behavior, and spatial memory deficits, whereas Rfwd2+/− female mice showed subtle deficits in social communication and spatial memory but were normal in anxiety-like, repetitive, and social behaviors. These autistic-like behaviors in males were accompanied by a reduction in dendritic spine density and abnormal synaptic function on layer II/III pyramidal neurons in the prelimbic area of the medial prefrontal cortex (mPFC), as well as decreased expression of synaptic proteins. Impaired social behaviors in Rfwd2+/− male mice were rescued by the expression of ETV5, one of the major substrates of RFWD2, in the mPFC. These findings indicate an important role of RFWD2 in the pathogenesis of autism.

Systemic histone deacetylase inhibition ameliorates the aberrant responses to acute stress in socially isolated male mice.

Adverse experiences in early life can induce maladaptive responses to acute stress in later life. Chronic social isolation during adolescence is an early life adversity that can precipitate stress-related psychiatric disorders. We found that male mice after 8weeks of adolescent social isolation (SI) have markedly increased aggression after being exposed to 2h of restraint stress (RS), which was accompanied by a significant increase of AMPA receptor- and NMDA receptor-mediated synaptic transmission in prefrontal cortex (PFC) pyramidal neurons of SIRS males. Compared to group-housed counterparts, SIRS males exhibited a significantly decreased level of histone H3 acetylation in PFC. Systemic administration of class I histone deacetylase inhibitors, romidepsin or MS-275, ameliorated the aggressive behaviour, as well as general social interaction deficits, of SIRS males. Electrophysiological recordings also found normalization of PFC glutamatergic currents by romidepsin treatment of SIRS male mice. These results revealed an epigenetic mechanism and intervention avenue for aggression induced by chronic social isolation. KEY POINTS: Adolescent chronic social isolation can precipitate stress-related psychiatric disorders. A significant increase of glutamatergic transmission is found in the prefrontal cortex (PFC) of socially isolated male mice exposed to an acute stress (SIRS). Treatment with class I histone deacetylase (HDAC) inhibitors ameliorates the aggressive behaviour and social interaction deficits of SIRS males, and normalizes glutamatergic currents in PFC neurons. It provides an epigenetic mechanism and intervention avenue for aberrant stress responses induced by chronic social isolation.

The role of fruitless in specifying courtship behaviors across divergent Drosophila species.

Sex-specific behaviors are critical for reproduction and species survival. The sex-specifically spliced transcription factor fruitless (fru) helps establish male courtship behaviors in invertebrates. Forcing male-specific fru (fruM) splicing in Drosophila melanogaster females produces male-typical behaviors while disrupting female-specific behaviors. However, whether fru's joint role in specifying male and inhibiting female behaviors is conserved across species is unknown. We used CRISPR-Cas9 to force FruM expression in female Drosophila virilis, a species in which males and females produce sex-specific songs. In contrast to D. melanogaster, in which one fruM allele is sufficient to generate male behaviors in females, two alleles are needed in D. virilis females. D. virilis females expressing FruM maintain the ability to sing female-typical song as well as lay eggs, whereas D. melanogaster FruM females cannot lay eggs. These results reveal potential differences in fru function between divergent species and underscore the importance of studying diverse behaviors and species for understanding the genetic basis of sex differences.

Heatwaves inflict reproductive but not survival costs to male insects.

Climate change is having a dramatic effect on the environment, with rising global temperatures and more frequent extreme climatic events, such as heatwaves, that can hamper organisms' biological functions. Although it is clear that sudden and extreme temperatures can damage reproductive processes, there is limited understanding of the effects of heatwaves on male mating behaviour and reproductive success. We tested for the effects of heat stress induced by ecologically relevant heatwaves (33°C and 39°C for five consecutive days) on the mating behaviour, reproductive success, body mass and survival of male field crickets Gryllus bimaculatus, paired with untreated females. We predicted life-history and reproductive costs would increase with increasing heatwave intensity. Consistent with our expectations, males exposed to the highest heatwave temperature produced the fewest offspring, while having to increase courtship effort to successfully mate. Males also gained relatively more weight following heatwave exposure. Given that we found no difference in lifetime survival, our results suggest a potential trade-off in resource allocation between somatic maintenance and reproductive investment. Taken together, our findings indicate that sublethal effects of heatwaves could reduce the growth and persistence of animal populations by negatively impacting reproductive rates. These findings highlight the need for considering thermal ecologies, life history and behaviour to better understand the consequences of extreme climatic events on individuals and populations.

"Girl Math, Boy Math": The Presence of Toxic Masculinity in TikTok and X Jargon

Jargon or slang words have become a norm in everyday online discourses and conversations, with a recent emergence of gendered terminology classifying activities and fashion aesthetics into a type of “girl” or “boy”, both heavily popularized thanks to social media. A notable example is seen in the recent rise of gendered-specific jokes called “girl math”, which is a comedy created by women on the justification of impulse shopping. This phenomenon began to give way to its counterpart called “boy math”. Initially, mockery on male behavior began to expand into the areas of critiquing toxic masculinity and misogyny in society as a whole. Through sampling data from accounts that receive high traction from using such terms on the platforms of X and TikTok, the researcher is interested in conducting an intertextual research using the framework of appraisal and feminist theory in order to elucidate the linguistic nuances and cultural influences stored within these gender-specific terms, ultimately unveiling how they critique male hegemony. This research is hoped to contribute to furthering the understanding of how technology, social media, and language intersect, shaping both learning environments and societal perceptions of gender roles.
 Keywords: X, TikTok, appraisal theory, language evaluation, misogyny, toxic masculinity

Synaptic pruning during adolescence shapes adult social behavior in both males and females.

Evolutionarily conserved, peer-directed social behaviors are essential to participate in many aspects of human society. These behaviors directly impact psychological, physiological, and behavioral maturation. Adolescence is an evolutionarily conserved period during which reward-related behaviors, including social behaviors, develop via developmental plasticity in the mesolimbic dopaminergic "reward" circuitry of the brain. The nucleus accumbens (NAc) is an intermediate reward relay center that develops during adolescence and mediates both social behaviors and dopaminergic signaling. In several developing brain regions, synaptic pruning mediated by microglia, the resident immune cells of the brain, is important for normal behavioral development. We previously demonstrated that during adolescence, in rats, microglial synaptic pruning shapes the development of NAc and social play behavior in males and females. In this report, we hypothesize that interrupting microglial pruning in NAc during adolescence will have persistent effects on male and female social behavior in adulthood. We found that inhibiting microglial pruning in the NAc during adolescence had different effects on social behavior in males and females. In males, inhibiting pruning increased familiar exploration and increased nonsocial contact. In females, inhibiting pruning did not change familiar exploration behavior but increased active social interaction. This leads us to infer that naturally occurring NAc pruning serves to reduce social behaviors toward a familiar conspecific in both males and females.

No fitness effects of same-sex copulations in male red flour beetles.

Same-sex sexual behavior occurs in diverse animal taxa, yet its evolutionary maintenance is poorly understood as such behavior seems to be costly and does not directly increase reproductive success. We used male Tribolium castaneum beetles, which frequently engage in same-sex copulations, to test if same-sex sexual behavior influences future male mating behavior and reproductive success of males. Furthermore, we tested whether same-sex sexual behavior has benefits via indirect sperm translocation. We conducted a series of mating trials demonstrating that males exposed to same-sex behavior did not sire less offspring compared to control males that did not engage in same-sex behavior. This suggests that same-sex copulations did not lead to fitness costs in subsequent mating interactions. In addition, we found no evidence that indirect sperm translocation via an intermediate male occurs in T. castaneum. Taken together, these results imply that same-sex sexual behavior in males is associated with no costs in terms of lower mating rate and reduced siring success and does not seem to entail benefits. Moreover, our data conform to the hypothesis that sexual indiscrimination is prevalent in this species, which may explain the relatively high frequency of same-sex sexual behavior in T. castaneum.