Termites eat wood, but cannot break down wood on their own. They must have a small microbe in their intestine to break it down for them. The microbe in turn receives food and shelter.

Ostriches and gazelles feed next to each other. They both watch for predators. Because the visual abilities of the two species are different, they can each identify threats that the other animal may not see as readily. Both species benefit.

A tapeworm in humans is not all that uncommon. The tapeworms will hook on to the inner lining of the small intestine and absorb food from the human.

Most holes used by bluebirds for nesting are chiseled out by woodpeckers. Bluebirds never use a woodpecker hole unless it has been abandoned.

The spider crab and the algae can be found together in the ocean. Spider crabs live in shallow areas of the ocean floor, and greenish-brown algae lives on the crabs' backs, making the crabs blend in with their environment, and unnoticeable to predators.

Wasp larvae, as they hatch, will feast on a caterpillar. The caterpillar is weakened from the lack of food.

The oxpecker bird and the rhinoceros have a relationship. The oxpeckerreceives protection and obtains food from the ticks and other pests infecting the rhino’s skin. The rhino receives in return cleaning and early warning of approaching danger.

Leeches cling to a turtle’s skin and suck blood and microorganisms from the turtle, not to mention valuable food and nutrients.

The plover bird sits in a crocodile’s mouth and eats the food in the crocodile’s teeth. Meanwhile, the crocodile gets a clean mouth and can continue hunting.