Sperm Competition in Non-Humans

The law of survival of the fittest requires the member who outshines and out rules all other members of the specie only to secure a chance to create progeny. It is reasonable that securing one's desired mate is crucial to this process. Animals have evolved to compete with other members regarding their anatomical structure. One such aspect is the nature, quality, and behavior of their sperms.

The following text will cover different ways the evolutionary process has made organisms adapt to secure the highest chance of reproduction by regulating their sperm. It will cover this phenomenon among insects and primates and discuss the impact of sperm competition and how it leads to reproductive success.

What is Sperm Competition?

When two or more males mate with the same female, their sperm compete to fertilize her eggs. This process is known as sperm competition. In evolutionary psychology, sperm competition has received much attention since it is crucial to the evolution of sexual selection and reproductive action plans in non-human animals. The notion of sperm rivalry among non-human animals will be discussed in the following material, along with its consequences on reproductive success and the development of sexual behavior.

Sperm Competition Among Primates

Sperm competition in primates is a complex and multifaceted phenomenon extensively studied by evolutionary biologists. Primates are a diverse group of animals that includes lemurs, lorises, tarsiers, monkeys, and apes. They exhibit various reproductive strategies, from monogamous pair bonding to polygynous mating systems where one male mate with multiple females. Male chimps have developed enlarged testicles that produce more sperm and more extended periods of copulation, allowing them to deposit more sperm into the female's reproductive canal and increase their chances of passing on their genes. They may also discharge seminal fluid, which contains chemicals that either increase the mobility of their sperm or decrease the mobility of the sperm of other males.

Gorillas are another instance of sperm competition in primates. Gorillas live in tiny groups, and the dominant male usually mates with all the females. Conversely, females may mate with subordinate males, which implies that sperm from multiple males may compete to fertilize their eggs. Male gorillas have enlarged testes and generate more sperm to offset this. They also engage in sperm competition guarding, which involves remaining near the female after mating to prevent other males from mating with her.

Sperm Competition in Insects

The fruit fly (Drosophila melanogaster), another example of sperm rivalry in insects, is a good case. The male will try to mate with a female once he finds her. However, given that females may keep sperm in their reproductive system for a few days, numerous males can fertilize the same female's eggs. Male fruit flies have evolved longer sperm that can outcompete the sperm of other males and larger testes that produce more sperm to resist this.

The bed bug (Cimex lectularius) is a remarkable example of sperm competition in insects. Male bed bugs have developed a unique strategy to guarantee that their sperm fertilize a female's eggs. During mating, a male bed bug injects a gelatinous material known as the mating plugs into the female's reproductive system. This plug blocks the feminine reproductive cavity, inhibiting mating attempts from other males. Other men's sperm cannot fertilize the female's eggs because the plug also contains a substance harmful to male sperm. Additionally, they create seminal fluid, which contains proteins that can compete with other males' sperm and reduce their ability to fertilize eggs.

Insect species, including crickets, beetles, and spiders, have also been found to compete for sperm. Many of these male species have developed complex reproductive features like suction cups or spiny genitalia that allow them to hold onto the female during copulation and stop other males from mating with her. Additionally, they might create substances that displace or poison the sperm of other males.

Impact of Sperm Competition on Reproductive Success

Sperm competition can have a significant impact on reproductive success. Males exposed to sperm competition generate more offspring than males not subjected to competition in some species. For example, males exposed to competition from other males generate more offspring than males not subjected to competition in the fruit fly Drosophila melanogaster. This shows sperm competition can boost reproductive success in males who can compete effectively.

However, the impacts of sperm competition on men are not always good. In rare situations, sperm rivalry might reduce the quality of a male's sperm. Males subjected to competition from other males, for example, in the red junglefowl (gallus), generate sperm that is less motile and has a lower fertilization rate. This shows that the costs of mass-producing sperm in response to the competition may outweigh the benefits

Sperm competition has an impact on the evolution of sexual conduct. In the presence of competition from other individuals, males and females have evolved different tactics to maximize their reproductive success. Men, for example, may physically compete with other men for access to females, while females may mate with many males to maximize their chances of fertilization. Because of the selective pressures exerted by sperm competition, these habits have evolved.


Sperm competition is a phenomenon that occurs when two or more males mate with the same female, and their sperm compete to fertilize her eggs. The concept of sperm competition has been studied extensively in evolutionary psychology, as it plays a significant role in the evolution of reproductive strategies and sexual selection among non-human species. Sperm competition can lead to an increase in reproductive success for males that can compete effectively.

Updated on: 05-May-2023


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