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12 Examples of Commensalism Relationships

Commensalism is a type of symbiotic relationship in which one organism benefits while the other organism is not affected either positively or negatively. In other words, the commensal organism benefits from the relationship, while the host organism is neither helped nor harmed. Commensalism most often occurs between two different species, but can occasionally be seen between members of the same species. In this article, we provide 12 examples of commensalism relationships.


Commensal relationships can be seen in a variety of ecosystems and environments, from the deep sea to the rainforest canopy. While commensalism is generally considered a neutral relationship, it can have important ecological implications, including affecting the distribution and abundance of species.

12 Examples of commensalism relationships

1. Barnacles and whales

Barnacles on humpback whale tail
Barnacles on humpback whale tail | image by Barb Ignatius via Flickr | CC BY 2.0

One example of commensalism is the relationship between barnacles and whales. Barnacles are small crustaceans that attach themselves to the skin of whales, where they feed on plankton and other tiny organisms in the surrounding water.

The barnacles benefit from the protection provided by the whale’s skin, which shields them from predators and helps them move through the water more easily. While the whale is not directly affected by the barnacles, the additional weight may increase drag and require more energy to swim.

2. Remoras and sharks

Remora and shark
Remora and shark | image by Brian Snelson via Flickr | CC BY 2.0

The Remoras are fish that latch onto sharks using a unique suction cup, where they feed on scraps of food left over from the shark’s meals. In addition to feeding on scraps, remoras benefit from the protection provided by the shark’s from predators, while also saving considerable amounts of energy by being pulled through the water.

There is no benefit to the shark by having the remoras around, but they are not affected by their presence and don’t waste energy by trying to prey on such small fish.

3. Pilot fish and sharks

Pilot fish and shark underwater
Pilot fish and shark underwater | image by OldakQuill via Wikimedia Commons | CC BY-SA 3.0

Very similar to the remoras example, pilot fish benefit from the protection provided by the shark’s presence, as they are less likely to be eaten by other predators. The pilot fish also feed on the scraps of food left over from the shark’s meals. The main difference with the pilot fish and remoras relationships with sharks is that pilot fish will swim alongside sharks, rather than attaching themselves.

4. Epiphytes and trees

Epiphytes on tree
Epiphytes on tree | image by Bernard DUPONT via Flickr | CC BY-SA 2.0

The Epiphytes are plants that grow on other plants without harming them. These plants obtain nutrients and water from the air and rain, rather than from the host plant, and use the host plant only for support.

Examples of epiphytes include orchids, mosses, and ferns. Epiphytes are typically transported to trees via birds or strong winds, and they further benefit by being closer to immediate sunlight in the higher canopy.

5. Birds and trees

Pileated woodpecker
Pileated woodpecker

Birds often use trees for nesting, roosting, and feeding, without affecting the tree in any significant way. Birds such as woodpeckers, for example, drill holes in trees to create nesting sites, while other species of birds use the branches of trees for perching or feeding.

There may be some damage to the bark, branches and leaves of trees as a result of some bird species, particularly woodpeckers. Fortunately the damage is so little that this is still considered a commensal relationship.

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6. Cattle egrets and livestock

cattle egrets and cows

The Cattle egrets are birds that are commonly found in fields and pastures where livestock graze. The birds feed on insects and other small organisms that are stirred up by the movement of the livestock.

As the name suggests, cattle egrets are usually found around cows and other cattle species. The cattle egrets benefit from the easy availability of food, while having no noticeable impact on the livestock.

7. Bacteria and human skin

Man with skin disease
Man with skin disease

There are trillions of bacteria that live on the surface of human skin, and many of these bacteria are commensal. While some bacteria can cause infections, many species of bacteria live on human skin without causing any harm.

Some bacteria may even benefit humans by producing compounds that help to protect against harmful pathogens. The commensal bacteria benefit from the warm, moist environment provided by human skin, while humans are not affected by the presence of these bacteria.

8. Shrimps and sea urchins

Sea urchins surrounded with algae
Sea urchins surrounded with algae | image by Gary Todd via Flickr

Some species of shrimp are known to live on the spines of sea urchins. The shrimp benefit from the protective environment provided by the sea urchin, which shields them from predators, while the sea urchin is not harmed or benefited by the presence of the shrimp.

9. Hyenas and lions

Young male lion and hyenas
Young male lion and hyenas

Lions are proficient hunters that are capable of taking down large prey items, often too big to be fully consumed. Hyenas are known to scavenge the kills of lions once they have had their fill, and in doing so benefit from the easy availability of food.

While the presence of hyenas may be seen as a nuisance by lions, they are not affected by their presence in a commensalistic sense.

10. Sea cucumbers and emperor shrimp

Emperor shrimp on sea cucumber
Emperor shrimp on sea cucumber | image by Bernard DUPONT via Flickr | CC BY-SA 2.0

The Emperor shrimp are small, brightly colored crustaceans that are often found living on the surface of sea cucumbers. The shrimp are able to use the sea cucumber as a place to hide from predators, as well as a source of food.

The sea cucumber is not affected by the presence of the shrimp. It continues to go about its normal activities, such as feeding and moving along the seafloor.

11. Beetles and pseudoscorpions

Pseudoscorpion on wood
Pseudoscorpion on wood | Photo credits: Deposit Photos

The Pseudoscorpions are small arachnids that live in decaying wood on the forest floor. They are incredibly small, which makes travelling to new patches of decaying wood difficult.

However, the pseudoscorpions will attach themselves to the abdomen of beetle species, sometimes up to 30 individuals, and detach when they arrive at a new wood pile. Although a minor inconvenience, the beetle is not negatively affected by the small hitchhikers.

12. Hermit crabs and shell

Hermit crab and shells
Hermit crab and Shells

The Hermit crabs are intriguing creatures that have a unique relationship with shells. They have a vulnerable abdomen that requires protection, and they use their sharp claws to grasp onto the shell. Hermit crabs exhibit a diverse range of colors and sizes, with some species having intricate patterns on their shells.

Shells, on the other hand, serve as a perfect solution for hermit crabs’ protection. They are the rigid external skeletons of marine animals, such as snails, and are available in different shapes, sizes, and colors. The shells act as a safe haven for hermit crabs, and they can even switch shells as they grow.