• Biology Ecology Interactions Among Organisms Competition
  • Competition

    It’s a struggle, a fight, two entities opposing each other for a desired outcome. We see the forces of competition at work in our everyday lives- feuding political parties, commercial product markets, rivaling athletics. Competition happens when two parties want the same thing, but there isn’t enough of it to go around…so they compete for it.

    What Do Organisms Compete For?

    Organisms compete for the resources they need to survive- air, water, food, and space. In areas where these are sufficient, organisms live in comfortable co-existence, and in areas where resources are abundant, the ecosystem boasts high species richness (diversity). The more generalist an organism is, the better chances it has to co-exist with its conspecifics (other members of the same species) and other taxa. Animals and plants that have specific life history requirements, like cavity-nesting birds, plants with ph-specific soil requisites, or animals with obligate feeding behaviors, have a more difficult time competing. These resources can be limiting factors for where organisms are distributed, and competition for them can be fierce.

    Types of Competition

    A fundamental concept in ecology is the competitive exclusion principle. This states that two species with similar ecological niches cannot exist sympatrically (in the same environment). One will always out-compete the other, so the more competitive species will stay and the subordinate one will either adapt or be excluded (by either emigration or extinction). While competition in the natural world is eminent, it doesn’t always happen in the same way.

    Interspecific competition is when different animals that live in the same geographic area (sympatric species) compete for the same set of resources, mostly food and space. Intraspecific competition is when different species compete with each other, usually for more specific requirements like mates and nesting/denning sites. Direct competition occurs when individuals compete with each other directly for the same resource, ie: two bull moose battling for access to a single female. Indirect competition occurs when organisms use the same resource, but don’t necessarily interact with each other- for example, diurnal cheetahs and nocturnal leopards using the same waterhole in a grassland savanna. Interference competition is when there is a deliberate displacement of individuals by their competitor. The less competitive individuals are forced to go elsewhere to find resources. Studies have shown, however, that if the more competitive animals leave, the displaced individuals will return. Exploitation competition is more subtle. This occurs when a species’ survival or reproduction is suppressed because of the presence of a staunch competitor. There is no actual displacement, as the competitive pressure manifests itself through a reduction in an individual’s ability to survive and reproduce.

    Forces of Competition

    Defensive Behavior

    When an animal has found a space that contains all the resources it needs to survive, it wants to hold on to it. This is why many animals are territorial; they defend their territory which contains those resources. Animals defend territories for many different types of resources: a convenient source of fresh water, an ample supply of vegetation, proximity to a stable source of prey, denning sites, etc. Animals advertise their ownership of these territories by visual and chemical signals that deter their competitors from encroaching on their turf. If these signals are ignored, and the boundaries of the territory are breached, a territorial battle is sure to ensue.

    Aggressive Behavior

    Animals exhibit aggressive behavior when one of their resources is compromised. Males may compete over an existing territory, available females, nesting sites, or breeding rights in a social hierarchy. Defensive behaviors often lead to aggression if problems can’t be sorted out through threatening displays or intimidation. In most cases, animals would prefer to avoid antagonistic encounters because it requires a huge expenditure of energy to participate in an aggressive interaction, but the resources they are aiming to protect are vital enough that they are willing to risk it if necessary.

    Competition of the Herbivorous Kind

    Competition isn’t just a phenomenon in the animal world; plants compete with each other too. They need adequate sunlight, soil nutrients, and fresh water to survive. Though they are stationary, they still have ways of combating each other. Over time plants have evolved ingenious ways of procuring sunlight, attracting pollinators, and obtaining fresh water. They may take an offensive approach, responding to the competition head-on, or a defensive approach, making modifications to increase their chances of survival and reproduction. For example, when sunlight is the limiting factor, some forest trees grow rapidly to tower over their competitors and absorb the most sunlight, others channel their energy into producing many seeds and attempting to spread them so that they increase the chances of their offspring landing in a well-lit area. Plants have developed all kinds of competitive strategies from storing nutrients to becoming parasites to developing disease resistance.

    How to Avoid Competition- Isolate Yourself

    Nature is am amazing beast; it has mechanisms in place to allow species to exist in the same place at the same time using the similar resources. This is the beauty of niche separation and is the answer to the competitive exclusion principle. Different species have different life requirements, eat different foods, live in different habitats, and behave differently, all in the name of sharing resources. Sometimes, however, there is just no way around it, organisms have to share the same resources, and in this instance, nature has the uncanny ability to adapt. So if you’re an animal or a plant that can’t hack the competition, your best bet is to avoid it, and plants and animals have developed some pretty clever ways to isolate themselves from each other.

    Geographic Isolation

    One method of isolation is geographic isolation- not being in the same place at the same time. Animals that are geographically separated have a better chance of obtaining the resources they need. This isolation can occur through animals having different geographic distributions or by participating in seasonal migrations. Geographic separators might be an expanse of land, a mountain range, a body of water, or an elevation gradient.

    Behavioral Isolation

    This occurs when animals have contradictory behaviors that prevent them from competing with each other. For example, by day, birds rule the air. They forage, maintain territories, reproduce, and compete with each other for the best available resources. By night, however, bats rule the roost. Come dusk there is a taxonomic tango when the diurnal (active by day) organisms retire for the evening and the nocturnal (active by night) organisms commence their daily follies. By the cover of night nocturnal organisms avoid competitive interactions with their diurnal counterparts. In some ecosystems, the nightly taxonomic exchange is quite the spectacle. Certain night-blooming flowers open their blossoms to be pollinated by bats. Insects emerge to forage after spending the day avoiding hungry birds.

    Foraging habits are another way that organisms can avert competing with each other. Take raptors for example. A red-tailed hawk is a generalist predator; they eat anything from rodents to reptiles to other birds. They are good competitors with other birds of prey because they consume a wide variety of prey so their options are many. Specialist predators, however, like the osprey, which eats strictly fish, are limited in their prey selection as well as their geographic range because they have to live in areas where their prey resides. Take two similar animals then that inhabit the same geographic area and eat the same type of food…what then? Herbivorous rhinos deal with this conundrum by consuming different parts of plants. White rhinos have flat, wide lips for grazing grasses while black rhinos have pointed, dexterous lips for browsing shrubs.

    Mechanical Isolation

    The lip morphology of rhinos is an evolutionary expression of a behavioral trait that separated rhinos long ago. Today there are many animals that have morphological differences that directly allow them to avoid competition with other organisms. Like giraffes who’s browse line is way above that of the other browsers it resides with, and hyenas whose jaw structure and musculature is strong enough to consume the hides and bones of carcasses left behind by other predators. Sometimes isolation mechanisms influence each other, adding another impediment to competition. Organisms that have been geographically separated for long periods of time can evolve morphological and behavioral changes that prevent them from breeding with each other.

    All these methods of isolation are changes that have occurred over many generations. Organisms have evolved over time to avoid competition and the changes have become incorporated in their life histories. The most awesome thing about evolution is that it never stops! As the environment changes and new stressors are added to an ecosystem, that pressure influences organisms to change, thus making them better competitors.
    Competition plays a very important role in ecology and evolution. The best competitors are the ones who survive and get to pass on their genes. Their progeny (offspring) will have an increased chance of survival because their parents out-competed their conspecifics. The best competitors have the best fitness, which is a measure of the genes that are passed on to succeeding generations. So the best competitors are the best survivors, which have more offspring, which means that more competitive genes are perpetuated in the gene pool. It is important to note that these changes occur over very long periods of time and the life history characteristics of organisms we see today are the results of changes that happened over millennia.

    The Trade Off

    These rewards are not without consequence. Sometimes being a good competitor in one area means that you are lacking in another. Take Australian lyrebirds for example. They have long, beautiful tail plumes as ornaments to attract female mates. The longer, more colorful their feathers are, the better competitors they are among other males, but this also means that they are more conspicuous. A colorful bird with long, elaborate feathers is not hard to miss, particularly when he is dancing and calling to attract a mate. The very characteristics that make him a good competitor among his male counterparts are also a detriment to him as they also attract potential predators. The question then becomes…is advertising for female mates worth the risk of being discovered by a predator? What do you think?

    According to the ‘closed community concept’ in the world of bird behavior, established communities are one way to avoid competition. For example, when an aggregation of birds can successfully co-exist without significantly compromising each other’s ability to acquire resources, they prefer this stability. By maintaining the community they resist invasion by other potential competitors. Communities can be made up of a single species, or there can be mixed species colonies.

    mixed-colony-birds-es

    Mixed seabird colony- great crested terns and brown boobies
    Kia Island, Fiji

     

    Competition as a Regulator

    When two organisms or populations compete with each other, whether it be directly or indirectly, one of several outcomes can be expected. In extreme cases one population (or individual) out-competes the other and the ‘losing’ organism becomes extinct from the area. If, however, the competition event is spread over time and the losing animal has time to respond and recover, they may relocate to another geographic area (emigrate). If the losing organism is not displaced, it may change its behavior or requirements to utilize different resources so that it is no longer in competition with its opponent.
    Intraspecific competition can serve as a regulator for population size. If a particular source of prey, or abiotic habitat feature is not readily available, then competition for the ones that are will be heavy. If the requirements are scarce enough, this will cause the population to remain stable, or decrease. If resources are readily available, then competition will be low and a population may increase.

    Foreign Contenders

    Sometimes competition can have a serious impact on an ecosystem, especially when invasive or exotic species are involved. When non-native organisms colonize a new area, they are sometimes better suited to compete with native organisms for resources. Once able to overcome the transition of the relocation, they can become very successful and out-compete native organisms, causing their populations to decline, or in extreme cases, become locally extinct.

    Human Competition

    As the human population continues to increase, humans are in competition with nature. Our requirements for survival are just as basic as those of plants and animals. We breathe the same air, drink the same water, and use the same space. Fortunately for us, we have intellect, which is the greatest competitive advantage to be had. We can use our brains to build tools and technologies that make us seemingly undefeatable. Unfortunately for us, our utilitarian attitude has cost us millions and millions of acres in forests, wetlands, coral reefs, and other precious habitats around the globe. While we might not be directly competing with plants and animals for food or potential mates, we are indirectly competing with them by consuming space, and while our population is increasing, theirs are declining.

    Humans directly compete with animals also; a prime example is the global overfishing conundrum. Oceans world-wide are experiencing massive declines in fish populations due to human over-harvest. Commercial fishing operations are way better suited to fish for prized commercial fish like tuna, cod, salmon, and crustaceans like shrimp and lobster. People out-competing natural predators means that we are taking too many, too rapidly, and populations of predator and prey are suffering.

    The Big Picture

    Understanding competition is a huge component of ecology. The way organisms compete with each other determines species distributions, population dynamics, community structure, food webs, and social dominance hierarchies. Competitive interactions over time manifest themselves in physical and behavioral adaptations that shape the evolution of a species. Human activity, invasive species, climate change, and environmental pressure are constant stressors on ecosystems, making resources less available and of less quality. These stressors affect the way that organisms compete with each other and their ability to survive and co-exist.

    Even Dr. Seuss Understood the Complexities of Competition

    And NUH is the letter I use to spell Nutches,
    Who live in small caves, known as Niches, for hutches.
    These Nutches have troubles, the biggest of which is
    The fact there are many more Nutches than Niches.
    Each Nutch in a Nich knows that some other Nutch
    Would like to move into his Nich very much.
    So each Nutch in a Nich has to watch that small Nich
    Or Nutches who haven’t got Niches will snitch.

    Dr. Seuss – On Beyond Zebra (1955)

    Questions to Ponder???

    If an animal in a given habitat has a similar ecological niche to another species, how would direct competition influence their interactions?

    What possible outcomes could there be if an exotic species is accidentally introduced to a stable, mixed-bird community?

    Can you give an example of another way that humans compete with nature?

    Written by Rob Nelson

    Rob is an ecologist from the University of Hawaii. He is also an award-winning filmmaker. As principle director of Untamed Science productions his goal is to create videos and content that are both entertaining and educational. When he's not making science content, he races slalom kayaks and skydives.

    You can follow Rob Nelson
    Comments

    Leave a Reply

    Your email address will not be published. Required fields are marked *

    − 3 = 5

    This site uses Akismet to reduce spam. Learn how your comment data is processed.