11.1.4.4. Commensalism

This is the interaction in which one species benefits and the other is neither harmed nor benefited. An orchid growing as an epiphyte on a mango branch, and barnacles growing on the back of a whale benefit while neither the mango tree nor the whale derives any apparent benefit.

Commensalism refers to a type of ecological relationship where one species gains benefits while the other species remains unaffected. For instance, when an orchid grows on a mango tree, it does not take resources from the tree to survive, thus not harming it, while it benefits from the elevated position to access sunlight. Similarly, barnacles attach themselves to whales. The barnacle benefits from the whale's movement through the water by gaining access to nutrient-rich waters, while the whale is not impacted significantly by having barnacles on it.

Imagine a friend who always wants to sit on your shoulders during a parade. Your friend can see the event better and celebrate, while you are carrying them without feeling burdened. In this way, your friend enjoys the view (benefit) without causing you any trouble (no harm). This again illustrates commensalism.

The cattle egret and grazing cattle in close association, a sight you are most likely to catch if you live in farmed rural areas, is a classic example of commensalism. The egrets always forage close to where the cattle are grazing because the cattle, as they move, stir up and flush out insects from the vegetation that otherwise might be difficult for the egrets to find and catch.

In the relationship between cattle egrets and grazing cattle, the egrets follow the cattle closely. As the cattle graze, they disturb the ground, revealing insects hidden in the grass. The egrets benefit by having easier access to food while the cattle are largely unaffected by their presence. This mutual arrangement allows the egrets to feed more successfully without posing any risk or competition to the cattle.

Think of it like a group project in school where one student (the egret) works best when another student (the cattle) does all the talking. The first student gains the benefits of clear ideas and contributions without having to do much themselves, while the talkative student is unaffected and gets to lead the project.

Another example of commensalism is the interaction between sea anemone that has stinging tentacles and the clown fish that lives among them. The fish gets protection from predators which stay away from the stinging tentacles. The anemone does not appear to derive any benefit by hosting the clown fish.

In this example, clown fish find safety among the stinging tentacles of the sea anemone. The anemone's stinging cells protect the clown fish from predators, creating a safe sanctuary for the clown fish to thrive. However, the anemone does not gain any advantage from the presence of the clown fish, which is why this interaction is classified as commensalism. It shows how species can interact in ways that benefit one while leaving the other indifferent.

Imagine a scenario where a small dog spends time in a pet shop. The big dogs can’t reach the shelves where the treats are, so they don’t bother the little dog. The little dog benefits by getting all the treats while the big dogs don’t mind and go on about their day, representing a classic commensalistic relationship.

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