Many large grazing animals, such as rhinoceroses and buffaloes, form strange partnerships with small birds. These birds, cattle egrets and tick birds are carried about on the backs of larger animals. There, they perform an important service by eating ticks and fleas that otherwise would suck the blood from the animal and cause dangerous diseases. This type of partnership is called symbiosis.
Other symbiotic partnerships exist in the animal world too. The plover, a small bird, lives on a crocodile’s body and even struts into the reptile’s open mouth to perform its valuable service, that of pecking leeches from the crocodile’s gums and cleaning its teeth. The crocodile seems so grateful to the tiny plover that it never harms the small bird.
The small cleaner fish performs the same “toothbrushing” service on larger fish by eating parasites and other rubbish from their teeth and bodies.