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Rodents: Rodentia

Rodents And People

Rodents play a vital role in the ecosystem. They serve as the prey for many animals and some animals will use their burrows for shelter and protection.

People have caused the loss of population of many species of rodents by destroying their natural habitat, harming them directly, or introducing species that prey on rodents. Many species of rodents are considered pests and even dangerous to humans. Rodents cost billions of dollars in lost crops each year, eating the grain stored during the winter and the seeds of plants. Beavers can cause destruction by damming up creeks, causing water to back up into areas where its not wanted.


Fossils show that the first rodents began scampering about an estimated fifty-four million years ago in Asia and North America. These original rodents were themselves descendants of rodent-like ancestors called anagalids, which also gave rise to the rabbits. It was not until about five million years ago that the modern Muridae family of rodents came on the scene. The murids (MYOO-rids) now make up more than half of all rodent species, including rats, mice, and hamsters. These mammals have flourished due to multiple, large litters and their ability to adapt quickly to environmental changes.

Rats carried the fleas that caused the plagues of Europe. Rats and mice help spread other deadly diseases as well, such as bubonic (byoo-BON-ik) plague and typhus (TIE-fus).

Rodents are important as sources of food for many people. Roasted, stuffed, or fried guinea pig, for example, is a popular dish in Ecuador, Peru, and other South American countries. In many parts of the world they have an economical importance for their fur, such as the chinchilla of South America, a rodent almost extinct in the wild but thriving in captivity.

Rodents such as mice and rats are also used extensively in medical research because their bodily processes are similar to humans' and they have a rapid reproduction rate. They are used to study many diseases and test medicines. People also use these and other rodents, such as guinea pigs, to test the safety of cosmetic and human food products. Many people also keep the small and "cute" rodents as pets.


In 1347 a ship from Caffa, on the Black Sea, came ashore at Messina, Sicily. Along with its goods, the ship was also carrying flea-infested rats. Most people on board were already dead, and the ships were ordered out of the harbor, but it was too late—the plague, or Black Death, had reached Europe. The disease, which may have begun in Asia or Egypt, killed within days of infection and the European population was quickly decimated. (The nursery rhyme "Ring Around the Rosy" is traced to the plague's rose-colored wounds). By 1349, the Black Death had swept through nearly every town and village in Britain. It is estimated that the plague killed a quarter of the European population, about twenty-five million people.

At that time, people blamed the plague on many causes, including fumes, God's wrath, and the unlucky alignment of planets. It is now known that the plague was caused by a bacterium that lived in the stomach of fleas. These fleas mainly infect rodents, particularly black rats. When the flea bites, either a rat or a human, it spits some bacteria out into the bite wound. The bacteria were passed from one rat to another by these fleas, causing the bacterium to spread. Large numbers of infected rats died and the fleas began biting humans.

Additional topics

Animal Life ResourceMammalsRodents: Rodentia - Physical Characteristics, Habitat, Diet, Behavior And Reproduction, Rodents And People - GEOGRAPHIC RANGE, CONSERVATION STATUS