Intrasexual Selection in Animals-AnimalBehaviorCorner

Intrasexual Selection in Animals

Intrasexual selection refers to the competition between individuals of the same sex within a species for access to mates or resources.

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In this article, we will delve into the captivating world of intrasexual selection in animals. We will uncover the various forms and mechanisms through which individuals vie for reproductive success and explore the fascinating implications it has for evolution.

By gaining a deeper understanding of intrasexual selection, we can unlock the secrets behind the development of extravagant physical attributes, the evolution of mating strategies, and the relentless battles for dominance within species.

So, join us as we embark on this enlightening journey into the realm of intrasexual selection and discover the hidden complexities that drive the evolutionary dynamics of the animal kingdom.

I. Intrasexual Selection in Mating Competitions

A. Male-Male Competition

Male-male competition is a fascinating aspect of intrasexual selection, where males vie for access to mates in a relentless battle for reproductive success. This phenomenon is widespread in the animal kingdom, with numerous species exhibiting remarkable examples of competition among males.

Intrasexual Selection in Animals-AnimalBehaviorCorner

Take, for instance, the powerful clashes between male elephants during musth, where they engage in intense fights to secure dominance and mating opportunities.

Similarly, male elk engage in fierce battles, locking antlers to establish their superiority and gain access to receptive females.

In male-male competitions, physical and behavioral traits play crucial roles in determining the outcomes.

Strong and robust individuals often possess an advantage, as their physical prowess enables them to overpower their rivals. They may have larger body sizes, impressive weaponry like antlers or horns, or intricate adornments such as colorful feathers or extravagant displays.

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Additionally, behavioral traits such as dominance, aggression, and territoriality can aid males in gaining an upper hand in the competition. These traits not only intimidate competitors but also signal their fitness to potential mates.

B. Female-Female Competition

While male-male competition often takes center stage, female-female competition is equally intriguing and influential.

In some species, females compete for limited resources or highly desired mates. This competition can manifest in various ways, depending on the species and the specific circumstances.

For example, in many bird species, females fiercely contest nesting sites that provide suitable conditions for raising offspring.

Intrasexual Selection in Animals-AnimalBehaviorCorner
Female Moorhens Fighting

The competition involves elaborate displays, aggressive behaviors, and vocalizations to establish dominance and secure the most advantageous nesting territories.

In other cases, females compete directly for access to high-quality males, particularly in species where male resources, such as food or territories, are limited.

Female spotted hyenas engage in intense competition for the opportunity to mate with the dominant male in their social group, and they display assertive behaviors to establish their position within the hierarchy.

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The strategies and tactics employed by females in competition can be diverse. They may exhibit enhanced reproductive capabilities, such as synchronized estrus cycles or heightened fertility signals, to attract and monopolize the attention of males.

Females may also engage in cooperative behaviors, forming alliances or coalitions to gain an advantage over competitors.

Additionally, subtle cues, such as body size, coloration, or physical condition, may be used to signal their competitive abilities and reproductive potential.

Understanding the dynamics of female-female competition adds depth to our knowledge of intrasexual selection, showcasing the diverse strategies and adaptations that have evolved to maximize reproductive success in females.

It highlights the complex interplay between individuals of the same sex, as they navigate the challenges and trade-offs associated with competing for limited resources or desirable mates.

II. Sexual Dimorphism and Intrasexual Selection

A. Sexual Dimorphism and Its Relationship with Intrasexual Selection

Sexual dimorphism refers to the pronounced differences in physical characteristics between males and females of a species. These differences can include size, shape, coloration, ornamentation, or weaponry.

Intrasexual Selection in Animals-AnimalBehaviorCorner
Female (left) and Male (right) Elephant Seals

Sexual dimorphism often arises due to the pressures of intrasexual selection, as individuals compete for access to mates or resources. It serves as a visual signal that aids in mate choice and competition, allowing individuals to assess the quality and fitness of potential partners.

B. Examples of Sexually Dimorphic Traits and Their Role in Intrasexual Competition

Numerous examples of sexually dimorphic traits exist across the animal kingdom, and these traits play critical roles in intrasexual competition. For instance, in many bird species, males possess vibrant plumage or elaborate courtship displays that capture the attention of females.

Peacocks flaunt their magnificent tail feathers during courtship, showcasing their genetic quality and attracting mates.

Similarly, male deer grow impressive antlers, which they use to engage in intense battles, demonstrating their strength and dominance to win access to females.

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Intrasexual competition among males can also be observed in the animal world through the presence of weaponry or physical adaptations.

Male elephant seals develop enormous size differences, with the dominant males growing significantly larger than their competitors.

These size disparities contribute to fierce battles for access to breeding territories and harems of females. The larger size and strength of the dominant males provide them with a competitive advantage, enabling them to fend off rivals and secure reproductive success.

C. Evolutionary Implications of Sexual Dimorphism

The evolution of sexual dimorphism through intrasexual selection has profound implications for the survival and reproductive success of species.

Intrasexual Selection in Animals-AnimalBehaviorCorner

By investing in elaborate traits or weaponry, individuals signal their genetic quality, health, or ability to secure resources, which in turn influences their attractiveness to mates. This selection pressure can drive the evolution of exaggerated and extravagant traits over time.

Sexual dimorphism also contributes to the diversification of species and the maintenance of genetic variation. Through intrasexual competition, certain individuals gain an advantage in mating opportunities, leading to differential reproductive success.

This process can result in the selection of specific traits, which become more prevalent in the population.

Over generations, sexual dimorphism may become more pronounced, as individuals with exaggerated traits continue to outcompete their rivals and pass on their genes to the next generation.

In conclusion, sexual dimorphism and intrasexual selection are intricately linked. Sexually dimorphic traits serve as signals in the competition for mates and resources, shaping the dynamics of reproductive success within a species.

The evolutionary implications of sexual dimorphism highlight its role in driving the diversification of species and the perpetuation of genetic variation.

By understanding the mechanisms behind sexual dimorphism and its relationship with intrasexual selection, we gain valuable insights into the fascinating world of animal behavior and evolution.

III. Intrasexual Selection and Mating Strategies

A. Alternative Mating Strategies in Males

In the realm of intrasexual selection, males employ a variety of alternative mating strategies to maximize their reproductive success. These strategies often emerge when direct competition with dominant males is challenging or risky.

Intrasexual Selection in Animals-AnimalBehaviorCorner

One such strategy is exhibited by “sneaker males” who adopt a stealthy approach to reproduction. Sneaker males avoid direct confrontations by mimicking females or adopting inconspicuous appearances to gain access to females during their receptive periods.

By exploiting the distractions or vulnerabilities of dominant males, sneaker males can successfully mate and pass on their genes.

Another alternative mating strategy observed in males is the role of “satellite males.” These individuals forgo direct competition and instead adopt a satellite position near dominant males.

Satellite males may exhibit subdued behaviors or mimicry to avoid detection, enabling them to intercept mating opportunities with receptive females when the dominant male is occupied or distracted.

This strategy allows satellite males to circumvent the fierce competition for dominance while still securing reproductive success.

Examples of Species that Exhibit Alternative Mating Strategies

Various species showcase these alternative mating strategies in males. For instance, in certain fish species like cichlids and wrasses, sneaker males exploit the spawning territories of dominant males to fertilize eggs.

Intrasexual Selection in Animals-AnimalBehaviorCorner

Meanwhile, in elephant seals, smaller satellite males position themselves near the dominant males, patiently waiting for an opportunity to mate with the females in the harem.

These alternative tactics highlight the remarkable adaptability and resourcefulness of males in the face of intrasexual competition.

B. Alternative Mating Strategies in Females

Females, too, employ alternative mating strategies to navigate the intricacies of intrasexual selection and secure reproductive success.

One such strategy is known as “cryptic female choice”. Cryptic female choice refers to the ability of females to exert selective pressure on male sperm or embryos after mating has occurred.

This strategy allows females to control paternity and favor the sperm or embryos of higher-quality males, ensuring that their offspring have the best genetic advantages.

Cryptic female choice often involves physiological or anatomical mechanisms that enable females to bias fertilization or selectively retain certain sperm.

Another alternative mating strategy observed in females is “mate preference.” Mate preference refers to the active selection of specific males based on their desirable traits, behaviors, or resources.

Females may exhibit preferences for certain physical attributes, such as vibrant colorations or elaborate displays, which can serve as indicators of male genetic quality or fitness.

Intrasexual Selection in Animals-AnimalBehaviorCorner
Fruit Flies

Mate preference also extends to behavioral traits, where females choose mates based on courtship rituals, vocalizations, or displays of parental care.

By selecting high-quality mates, females enhance their offspring’s chances of survival and reproductive success.

Examples of Species Where Females Exhibit Alternative Mating Strategies

Numerous species demonstrate alternative mating strategies in females. For example, in certain bird species like peahens, females exhibit mate preferences for males with vibrant and elaborate tail feathers. Female birds use these physical attributes as indicators of male health and genetic quality.

Additionally, in insects like fruit flies, females possess the ability to selectively store and utilize sperm from preferred mates while discarding sperm from less desirable males.

These examples highlight the active role that females play in shaping the outcomes of intrasexual selection and their ability to exercise choice in reproductive processes.

By employing alternative mating strategies, both males and females can navigate the complexities of intrasexual selection and increase their reproductive success.

These strategies showcase the diverse mechanisms and tactics employed by individuals to overcome competition and secure mating opportunities.

Understanding the intricacies of these alternative mating strategies provides a deeper insight into the fascinating world of sexual selection and the evolution of reproductive behaviors.

IV. Intrasexual Selection and Evolutionary Arms Race

A. The Concept of an Evolutionary Arms Race in Intrasexual Selection

In the realm of intrasexual selection, a captivating phenomenon known as the evolutionary arms race unfolds. This concept refers to a continuous cycle of adaptation and counter-adaptation between individuals of the same sex engaged in competition.

Intrasexual Selection in Animals-AnimalBehaviorCorner
Cendrawasih (A species of Birds of Paradise)

As males compete for access to mates or resources, they evolve traits and behaviors that confer advantages in the competition. In response, females develop counter-strategies to resist or overcome these male adaptations.

This back-and-forth escalation drives the perpetual refinement and diversification of traits, leading to the evolution of more elaborate and complex adaptations over time.

B. Examples of Coevolutionary Dynamics Between Males and Females

The coevolutionary dynamics between males and females in intrasexual selection are exemplified by remarkable adaptations and counter-adaptations.

For instance, male birds of paradise exhibit extravagant displays and intricate plumage to attract females. In response, females have developed discriminating preferences for specific display traits, leading to the evolution of even more elaborate displays in males.

This coevolutionary process drives the perpetual refinement of traits in both sexes as males strive to outcompete rivals, and females become increasingly selective.

Another example can be seen in the evolution of genitalia in certain species. Male and female genitalia often exhibit complex morphologies that have evolved as a result of sexual conflict.

In some cases, males possess elaborate genital structures that increase their reproductive success by physically manipulating or removing the sperm of previous mates.

In response, females have evolved reproductive tracts with various mechanisms, such as barriers or structures that hinder or counteract these manipulations.

This arms race between male and female genitalia has led to intricate coevolutionary dynamics and remarkable diversity in reproductive traits.

C. Role of Intrasexual Selection in Driving Speciation

Intrasexual selection plays a pivotal role in driving the process of speciation, the formation of new species.

Intrasexual Selection in Animals-AnimalBehaviorCorner

The intense competition among individuals of the same sex for mates or resources can result in reproductive isolation and the divergence of populations.

As males and females evolve traits and behaviors that maximize their reproductive success within their specific ecological contexts, they may become incompatible with individuals from other populations or species.

For example, in certain insects like crickets or fireflies, distinct male courtship signals have evolved, which are finely tuned to the preferences of specific female populations.

Females of different populations become highly selective and responsive to the signals of their local males, leading to reproductive isolation and the eventual formation of separate species.

The arms race between males and females in intrasexual selection can also drive the evolution of reproductive barriers, such as differences in mating behaviors or reproductive timing, further contributing to speciation.

As individuals with different adaptations and preferences become reproductively isolated, genetic divergence occurs, eventually resulting in the emergence of distinct species.

By understanding the role of intrasexual selection in driving speciation, we gain insights into the fascinating mechanisms that fuel the diversity of life on Earth.

The interplay between competition, adaptation, and reproductive isolation shapes the evolutionary trajectories of species, highlighting the intricate dynamics of intrasexual selection and its profound implications for the evolution of biodiversity.

V. Intrasexual Selection Beyond Reproduction

A. Intrasexual Selection in Non-reproductive Contexts

Intrasexual selection, typically associated with competition for mates and reproductive success, extends its influence beyond the realm of reproduction. It also plays a significant role in shaping interactions and dynamics in non-reproductive contexts among individuals of the same sex.

Intrasexual Selection in Animals-AnimalBehaviorCorner

This form of selection occurs in various social species where individuals engage in competition for resources, social status, or access to desirable group positions.

B. Examples of Intrasexual Selection in Social Hierarchies and Group Dynamics

Social hierarchies and group dynamics provide rich examples of intrasexual selection in non-reproductive contexts.

In many species, individuals within a social group compete for dominance or high-ranking positions, which offer access to valuable resources or preferred mates.

Dominance contests, ritualized displays, or aggressive interactions are common strategies employed by individuals to establish and maintain their status within the group.

For instance, in primate societies such as chimpanzees, males engage in intense battles for dominance within their group.

Dominant males enjoy preferential access to food, mates, and social privileges. They display their dominance through vocalizations, displays of physical strength, and intimidation tactics.

Similarly, in certain bird species, individuals compete for prime territories or coveted perching sites, which provide better access to food resources or enhanced mating opportunities.

C. Adaptive Significance of Non-reproductive Intrasexual Selection

Non-reproductive intrasexual selection carries significant adaptive significance in shaping social structures and influencing individual fitness.

Intrasexual Selection in Animals-AnimalBehaviorCorner

Competition for resources, dominance, or social status ensures efficient resource allocation and promotes group cohesion.

By engaging in intrasexual competition, individuals with higher competitive abilities or advantageous traits secure preferential access to resources, increasing their chances of survival and reproductive success.

Furthermore, non-reproductive intrasexual selection promotes the maintenance of diversity and the evolution of specialized adaptations.

As individuals within a population or group vary in their competitive abilities or traits, this diversity allows for the exploration of different ecological niches and the exploitation of a wider range of resources.

Variation and competition among individuals can drive innovation and facilitate adaptation to changing environmental conditions.

Intrasexual selection in non-reproductive contexts also contributes to social learning and the transmission of advantageous behaviors or cultural practices within a group.

Individuals observe and learn from successful competitors, enhancing their own competitive strategies and increasing overall group efficiency in resource acquisition or defense.

Understanding the significance of intrasexual selection beyond reproduction provides valuable insights into the complex dynamics of social interactions and the adaptive processes that shape individual and group behaviors.

By studying the intricate mechanisms of competition and selection in non-reproductive contexts, we gain a deeper understanding of the evolutionary forces that influence the behavior and survival of species across various ecological settings.

VI. Frequently Asked Questions about Intrasexual Selection

What is intrasexual selection?

Intrasexual selection refers to the competition and mate competition that occurs between individuals of the same sex within a species. It involves the evolution of physical and behavioral traits that give individuals a competitive advantage in securing mates or resources.

How does intrasexual selection work?

Intrasexual selection works through various mechanisms such as direct combat, ritualized displays, or competitive behaviors.

Males or females within a species compete with each other to gain access to mates or resources, which can include territories, food, or social status. The individuals with the most favorable traits or strategies often outcompete their rivals and have increased chances of reproductive success.

What are examples of intrasexual selection in animals?

There are numerous examples of intrasexual selection in animals. In species like lions and elephant seals, males compete for control over a group of females by engaging in physical battles.

Male birds often display elaborate courtship behaviors or possess vibrant plumage to attract females, creating intense competition among males.

These are just a few examples of how intrasexual selection shapes behaviors and traits in animals.

What are the outcomes of intrasexual selection?

The outcomes of intrasexual selection can include the evolution of exaggerated traits, increased fitness of successful individuals, and the potential for speciation.

Through intrasexual competition, certain individuals gain an advantage in mating opportunities, leading to the selection and amplification of specific traits over time.

How does intrasexual selection contribute to species diversity?

Intrasexual selection plays a significant role in driving species diversity. Through competition and selection, individuals with advantageous traits or strategies have better reproductive success, passing on their genes to the next generation.

This process leads to the diversification of traits within a population and, over time, can contribute to the emergence of new species through reproductive isolation and genetic divergence.

Can intrasexual selection occur in females as well?

Absolutely. Intrasexual selection is not limited to males; females also engage in competition for mates or resources.

Females may exhibit mate choice preferences, engage in aggressive behaviors, or develop alternative mating strategies to increase their reproductive success.

Intrasexual selection in females can lead to the evolution of traits and behaviors that enhance their access to desirable mates or resources.

Is intrasexual selection exclusive to sexual reproduction?

Intrasexual selection primarily operates in the context of sexual reproduction, where individuals compete for mating opportunities. However, it can also occur in non-reproductive contexts, such as competition for social status, access to resources, or dominance within a group.

Intrasexual selection beyond reproduction contributes to the shaping of social structures and individual fitness within a species.

How does intrasexual selection relate to sexual dimorphism?

Intrasexual selection often drives the evolution of sexual dimorphism, which refers to pronounced differences in physical characteristics between males and females.

Traits selected through intrasexual competition can become exaggerated and differ between the sexes.

Male-male competition may lead to the evolution of larger size, weaponry, or elaborate displays, while female-female competition can shape traits related to mate choice and reproductive success.

Sexual dimorphism is a result of the interplay between intrasexual selection and the preferences of the opposite sex.

What is the role of intrasexual selection in animal behavior and evolution?

Intrasexual selection is a crucial driver of animal behavior and evolution. It shapes the development of physical traits, mating strategies, social hierarchies, and even the formation of new species.

By understanding intrasexual selection, we gain insights into the diverse adaptations and strategies that animals employ to enhance their reproductive success and survival in competitive environments.


Intrasexual selection in animals is a fascinating and dynamic process that drives competition and mate selection within a species.

Through intense rivalries and the evolution of advantageous traits, individuals strive to secure mating opportunities and gain access to resources.

This form of selection shapes behaviors, physical characteristics, and social structures, contributing to the diversity and complexity of animal life.

Understanding intrasexual selection provides valuable insights into the evolutionary forces that shape animal behavior and the remarkable strategies they employ to ensure reproductive success.

By unraveling the intricacies of intrasexual selection, we gain a deeper appreciation for the fascinating world of sexual selection and the role it plays in shaping the animal kingdom.

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