MadSci Network: Zoology

Re: What is a rodent?

Date: Mon Jan 13 15:51:58 2003
Posted By: Allison J. Gong, Ph.D., Lecturer
Area of science: Zoology
ID: 1042406615.Zo

Untitled Hello Allison!

What a nice name you have! Thank you for asking this question. I'll do my best to answer it for you.

First of all, a rodent is a mammal. Mammals are vertebrate animals (that is, they have a backbone) that are warm-blooded, have hair or fur, and feed their young with milk that is produced by the mother's mammary glands. Cats, dogs, monkeys, elephants, dolphins, bats, and YOU are all mammals. So am I. One of the characteristics that distinguishes mammals from other vertebrates (reptiles, fishes, birds, and amphibians) is something called heterodont dentition. That's just a fancy way of saying that they have different kinds of teeth -- for example, incisors for biting, canines for ripping and shredding, and molars for grinding.

This link will take you to a nice photo and explanation of mammalian teeth.

All mammals have different kinds of teeth, and a look inside your own mouth will confirm this. However, rodents have something special about some of theirs. Rodents have incisors -- these are the teeth in the very front of your mouth that you use when you bite into an apple -- that grow continuously throughout the animal's life. Common examples of rodents are mice, rats, hamsters, and beavers. If you get a chance to observe these animals, you'll see that they spend a lot of time chewing on things. They do that to keep their incisors from growing too long. If for some reason a rodent is unable to gnaw on things, its incisors can overgrow its mouth and cause difficulty in feeding or even damage to the animal's jaws.

Now I should probably warn you that there is another group of mammals, the lagomorphs (rabbits and hares), that also have incisors that keep growing. However, the lagomorphs have two pairs of incisors in the upper jaw only, and rodents have one pair of incisors in each jaw. It sounds like a minor difference, but if anyone ever says to you that a rabbit is a rodent, you'll be able to tell him or her very convincingly that it's not.

If you'd like to read more about rodents, this site has a lot of good information.

Thanks again for the question.

Allison J. Gong
Mad Scientist

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